Criteria for attractive musical scales (overview)

What is this about?

According to the theory of the three worlds, mathematics (ideal world) plays a part in physical processes (physical world). Without our subjective perception (mental world), however, we would not be able to notice any of this. I examine the way in which these very different worlds converge in reality with the example of musical scales. There are some riddles here, for instance why human cultures have created thousands of different musical scales, but every one of them uses the octave.

This constancy of the octave can easily be explained by resonance, which in the case of the octave is particularly striking because it corresponds to a mathematical ratio of 2:1. The higher tone of the octave vibrates with twice the frequency of the fundamental tone – an obvious example of how physics, mathematics and subjective perception come together.

In the preceding post I examined whether, with the help of mathematical considerations, we can find further intervals which occur in real musical scales. With only a few mathematical criteria, we found a first pool of intervals which have a high degree of affinity to resonance, i.e. the musical scale tone and the fundamental tone are in a frequency ratio which very easily produces a strong resonance.

Criteria for musical scale tones

Tone range

All musical scales known to me are situated within the range of an octave. This alone is amazing, and we have seen that all three worlds are involved in their creation.The crucial factor for the musical scale tones is their frequencies (f). What is decisive is not the absolute height of the frequency, but only its relative height in comparison with other tones. Below, the number 1 will denote the frequency of the fundamental tone and the number 2 the (doubled) frequency of the octave. All the musical scale tones must be situated between the fundamental tone and the octave; in mathematical terms, this means for the relative frequency f(ST)of the scale tone (ST) in relation to the fundamental tone:

    1 ≤ f(ST) ≤  2

2.  Resonance

The physical precondition for resonance to occur is that two frequencies are in a “rational” ratio. In number theory, “rational” describes a number which can be written as a fraction of two integers. In other words: f2 = m/n f(m andn are integers, f1 and f2 are the two frequencies). We now hypothesise that a musical scale tone (ST) is preferably in a ratio (M/N) to the fundamental tone (FT) in which a resonance can develop. In mathematical terms, this is expressed as follows:

    f(ST)  =  m/n   f(FT)

This precondition is part of the physical and mathematical worlds and, independently of subjective and cultural perception, a generally valid physical precondition for resonance, also in the non-acoustic sphere.If calculating with interval fractions is new to you, I would like to recommend the annexes, in which the calculation processes and their backgrounds are described in detail.

3.  Strong resonance

A resonance does not always occur equally quickly and equally strongly. Some intervals can therefore develop a resonance more quickly and more strongly than others. I hypothesise that a resonance is the stronger, the smaller m and n are, and I have examined, starting from number 1, what intervals we obtain with as small values as possible for m and n.Surprisingly, it turns out that all the small denominators up to 5 result in musical scale tones which we already know as the most important ones in our traditional European musical scales.The search also reveals that the absolute height of m and n is not the sole determining factor; rather, it comes down to the prime numbers which result from the integer factorisation of m and n. Here it turns out again that among the prime numbers, 5 is also the limit for the numerator.  With this in mind 6, 8 and 9, which are not prime numbers, can be factorised (6=2×3, 8=2×2×2 und 9=3×3) and used for resonances. 7, however, which is a prime number, cannot be factorised and is therefore already too high for m and n in practice.

  m and n should be as small as possible,

Or more precisely: In the integer factorisation of m and n, 5 should be the highest number.

Why integer factorisation? – The musical scale tone does not exist on its own, i.e. it should not only have a resonance in relation to the fundamental tone, but also in relation to the other musical scale tones. This results in compound resonances, mathematically speaking in fractions, in which numerator and denominator can often be reduced. This quickly turns an 8 into a 4, a 15 into a 3, and we again have very small m and n values. Examples will follow.

4. Further criteria

Resonance is not the only requirement for attractive musical scales. Musicians and listeners must also be able to distinguish between the tones. This is easier if there are not too many tones and if they are not too close together. These are not mathematical requirements, nor have they anything to do with resonance. The origin of this demand on a musical scale has something to do with our reception, i.e. with what we are able to perceive – that is, our mental world. With regard to this, our perception depend on the physics of our inner ear and on the physics of our brain. These criteria are thus a demand from the mental world, on the basis of the physical world. Evidently, all three worlds are involved in the creation of the many thousand different musical scales. The following are criteria that are not related to resonance:

4a)
 The number of the musical scale tones must not be too high.

4b) The musical scale tones must not be too close to each other.

Neither the number of tones nor their minimum distance from each other are the same in every culture. Besides resonance, there are further principles in music, namely that of interference and the higher/lower principle. If the tones are close to each other, music-related training provided by cultural experience may make precisely such tones interesting. However, this does not happen across the whole octave range of the musical scale, for if tones are very close to each other, the overall number of tones in the scale must still not become excessive. The distance between other tones must occasionally be wider again. A musical scale with quarter tones across the whole octave is conceivable but is unlikely to become prevalent in practice.Besides interferences and the higher/lower principle, there is a further principle, the variety principle. This has neither a mathematical nor a physical basis, but a mental one. If everything is the same, things become boring – and this also applies to the distances within a musical scale. This is why we do not experience the whole tone musical scale, which solely consists of identical intervals, as particularly exciting. Yet in combination with other scales with more variants, it is precisely that same whole tone musical scale which can provide an interesting contrast. Pieces of music that would only use whole tone musical scales would not be interesting for long. We thus have a further criterion which is not related to resonance:

4c) The distances in the musical scale should not all be identical.

4d) Fundamental tone principle:

The fundamental tone is the tone which holds the musical scale together. We will have a closer look at this in the section about ecclesiastical modes. As a consequence of the fundamental tone principle, we will always relate the musical scale tones to the fundamental tone.

We compare all the musical scale tones through the fundamental tone.


With the help of these conditions, we will examine our pool of intervals from the preceding post and filter out some first musical scales. Not surprisingly, they are musical scales which do not only have a simple mathematical structure, but also exist worldwide. They are certain pentatonic scales which are not only in use in their pure forms around the globe, but are also contained as a basic structure in more complex musical scales, such as our standard major scale. Firstly, we will have a look at the most resonant musical scales.


Here you can find an overview of the texts about the theory of the three worlds.


 

Fractions and Resonances

Resonance works through shared overtones

Resonance occurs when two vibratory physical objects vibrate together. What matters is the two objects’ natural frequency:

  • 1st degree resonance: both objects vibrate in the same frequency (f2 = f1).
  • 2nd degree resonance: one object vibrates in an overtonefrequency of the other
    (f2 = n * f1).
  • 3rd degree resonance: both objects vibrate in a shared overtone frequency
    (f2 = n/m * f1).

The 3rd degree resonance reveals itself by the fact that the ratio of the two frequencies corresponds to a fraction of integers (n/m). This 3rd degree resonance is what interests us, for it has an effect on musical scales and chords rather than the 2nd degree frequency, as is often assumed (for this, cf. previous post).

Example: the fifth

One string a' has a basic frequency of 440 Hz and a string e" the frequency of 660 Hz. In this case, the second overtone on string a' vibrates with 3 × 440 = 1320 Hz and the first overtone on string e" vibrates with 2 × 660 = 1320 Hz. The overtones on the two strings have the same frequency and string a' can stimulate string e" through this common overtone. The ratio of the two basic frequencies is 3/2.

Proposition

For resonance to be generated, the frequencies must have a ratio of a fraction with integers.

 Why integers?

When a vibration medium (string, basilar membrane) vibrates, standing waves are produced. These are characterised by the fact that the string does not vibrate at either end, but only in the middle, with one or several antinodes (bellies). The number of the vibration bellies in the middle must be an integer since otherwise the standing wave would not be zero at either end.

Assessing musical scale tones with the help of resonances

 As we can hear, octaves and fifths can easily be made to resonate (fifth experiment) and are characterised by very simple resonance ratios (f2/f1), namely 2/1 for the octave and 3/2 for the fifth. With very few mathematical preconditions, we can now find further musical scale tones:

Criteria for the tones of a musical scale

In the cases below, we look at the interval between the tone and its fundamental tone.

  1. The interval must be situatedwithin an octave: this means that the fraction of the two frequencies (musical scale tone to fundamental tone) must be ≥ 1 and ≤ 2.
  2. The interval must be able to resonate: numerator and denominator must be integers.
  3. The resonance should be as vibrant as possible: the denominator of the fraction should be as small as possible.

The last two criteria are crucial but require some explanation, and I will illustrate the reasons for this later. For the time being, however, I will take all three mathematical criteria as given and see whether they enable us to find further well-known intervals.

Generation of a pool of possible musical scale tones with the help of the three criteria

 We begin with the denominators, starting with denominators 1 and 2. Our musical scale already includes:

All the other tones with denominators 1 or 2 are situated outside our octave range (1-2). Therefore we look whether further well-known intervals result from denominator 3:

All the other tones with denominator 3 are situated outside our octave range. We therefore continue with denominator 4:

All the other tones with denominator 4 are situated outside our octave range. We therefore continue with denominator 5:

Any further fractions with denominator 5 are situated outside our octave range.

A thought in between  

What is striking here is the fact that fractions with the numerator 7 do not exist as intervals here in Europe. My proposition is that this has something to do with the fact that seven is a prime number. This can explain why 8/5 and 9/5 are intervals that we are accustomed to although the denominator and numerators in these fractions are higher than with 7/5. Eight is 2×2×2 and nine is 3×3. We will see later that we can also compare several intervals with each other to assess the resonance. In frequency analysis, a comparison of two intervals means that the fraction of one interval is divided by the fraction of the other interval. In this situation it is of advantage that we can reduce the fraction. A prime number does not provide us with this option, but with figures such as 8 or 9, a reduction is often possible, particularly if, with fifths and fours, we have 2 or 3 in the denominator. Examples will follow.

In the case of our generation of resonant musical scale tones, however, it follows that we ignore 7/4 and 7/5 because the 7 in the numerator is too high a prime figure.

We continue with denominator 6:

Denominator 6 thus does not produce any new tones.

We omit denominator 7 as a high prime number and go directly to denominator  8:

Thus denominator 8 produces two new intervals, namely the major second (9/8 and the major seventh (15/8). The numerator and the denominator may be quite high in both fractions, but they can be divided by 2, 3 and 5. Thus the fractions of the intervals in combination with musical scales and chords become reducible, and the intervals prove to be resonant.

This is the end of our search for tones, and we can list our findings in the order of ascending frequencies:

Pool of the strongly resonating intervals

The following is striking in this pool:

a) Most intervals used by us have very simple frequency ratios.

b) The fourth, with a low denominator and numerator, is the “fourth most logical” musical scale tone. However, this tone is never an overtone. Nonetheless it makes sense, both in the mathematical world (simple fraction), in the physical world (simple resonance ratios) and mentally (subjective musical hearing experience).

c) The minor second and the tritone are missing from our pool. Mathematically speaking, these tones are not simple fractions and sound correspondingly sharper.

In music, such sharpness is interesting, because it brings change and diversity, but these intervals definitively fail to reach the ideal of a smooth resonance.

We will see later how the tritone nonetheless fits well into the resonances in certain conditions, whereas the minor second always sounds sharp and thus becomes the actual leading tone in European music.

For the time being, however, we are leaving it at our pool of ten tones. This is sufficient for many musical scales, particularly those which are used most frequently.

Further thoughts in between

As is well known, mathematicians like prime numbers. In this respect, we can define the above-mentioned criterion 3 (as small as possible numbers for numerator and denominator) more precisely:

The 3rd criterion in more precise terms:

For an interval to be able to resonate well in combination with other intervals, the prime factorisation of the numerator and the denominator should result in the smallest prime numbers possible:

2 is better than 3
3 is better than 5
5 is better than 7
7 is already too high for practical purposes.

Intervals and rhythms

This is different from rhythms, where fraction ratios also play a part. Why this is different there, and why rhythms with 7 or 11 beats sound good, can be plausibly explained with the theory of the three worlds. More about this later.

From a pool to musical scales

We now look for further criteria for attractive musical scales. The pool we have found is not a musical scale yet, but merely our starting point from which tones for different musical scales can be compiled. Here, further criteria are applicable.

Further criteria

4th criterion: preferably, the musical scale tones should also to be able to enter into resonances with each other.

5th criterion: the musical scale has a fundamental tone (a so-called tonality), which has a very special function in the musical scale.

6th criterion: the musical scale tones must not be too close to each other; if they are, we as human beings (lay people) cannot distinguish between them any longer. This is a practical constraint from the mental world. In a purely mathematical world, any number of differentiations would be conceivable; in a real situation, this is not the case. More about the criteria for musicl scales on the following page.


This is a post about the theory of the three worlds.

“Breaking down” the Fifth

The fifth

Let us first have a look at the fifth. It is a feature of  practically all the musical scales of human cultures. Musical scales without this pure fifth do exist, but these musical scales strike me either as artificial and deliberately designed like the whole tone scales or rather uncommon like the Locrian mode. The blues scale makes use of the “blues note” – the “flat five”, a note close to the fifth known as the diminished fifth – but also uses the perfectly normal fifth. After the octave, the fifth is certainly the interval that occurs most frequently in all the thousands of musical scales on this earth.

Fifth and twelfth

Can this normal fifth be generated by resonance like the octave? Although it is not an overtone, it can still be reached through the overtones. Below, I will show how this works, namely with a short detour through the twelfth, the third overtone.

The graph with the vibrating overtones will serve to illustrate this:

Fig. 1: A vibrating string with the fundamental tone and the first four harmonics (overtones)

In Fig. 1 I have even described the third overtone as a fifth, which is actually wrong, for in reality it is a twelfth. Nonetheless, this tone immediately strikes us as a fifth when we hear it. In Fig. 2, you can see an example of fifths and twelfths on a piano keyboard:

Fig. 2: Octave and twelfth on the piano

In our example, the fundamental tone is a (capital) C. The first overtone, the octave, is a (small) c and the second overtone, the twelfth, a (small) g. In relation to the fundamental tone C, the small g is a twelfth, but in relation to the first overtone, i.e. the small c, the g is a fifth.

The frequency of the fifth

What about this c-g interval in terms of frequency? To find out, let us compare Figures 1 and 2: Tone 3 (g) is three times the fundamental vibration (C) and tone 2 (c) twice the fundamental vibration. Thus tone 3 (g) vibrates 3/2 times as fast as tone 2 (c). If we take the small c rather than the capital C as the fundamental tone, then the small g is the fifth. And in the fifth, the upper tone (g) vibrates 3/2 times as fast as the lower tone (c). This is generally applicable:

A tone which vibrates 3/2 times as fast as another sounds a fifth higher to us.

The three worlds in the fifth

The fraction 3/2 is the mathematical aspect of the fifth. We have deduced it through the physics of the string vibrations. At the same time, we complied with the previously mentioned conditions (constraints) from the mental world: if the quint is meant to be a tone of a musical scale, it must not be too far away from the fundamental tone. This applies to every tone of a musical scale; it must be within an octave. In mathematical terms, this means that the ratio between its frequency and the frequency of the fundamental tone must be between 1 (= fundamental tone) and 2 (= octave). The fifth satisfies this requirement with the frequency ratio of 3/2 = 1.5. In the case of the twelfth, the frequency ratio is 3, i.e. greater than 2, and thus the twelfth is not a note of the musical scale. We perceive it as a fifth, but as mentioned before, in the mental world we perceive the octave as the “same” tone.

The resonance experiment for the fifth

To illustrate the relationship between the fundamental tone, the fifth and the twelfth, I propose a further resonance experiment on the piano:

Fig. 3: Resonance experiment for the fifth. In comparison to Fig. 2, the key on which we investigate the resonance is now the fifth – the capital G – and not the small g.

To begin with, we again test the twelfth and press the twelfth (the small g) with the right hand like in the octave experiment . The string should not make a sound, but the key must be kept depressed. With the left hand, we briefly and vigorously hit the C, i.e. the fundamental tone. Like in the octave experiment, the depressed string (g) should make a sound although it was not hit. This is pure resonance; the string makes a sound because it was stimulated by sound waves. This works because the small g is an overtone of the capital C.

But what about the capital G, i.e. the fifth? To test this, keep the capital G mutely depressed while vigorously hitting the fundamental tone, i.e. the capital C. You can now hear a high tone. If you listen carefully, you will notice that this is not the fifth, i.e. the capital G, but the twelfth, i.e. the small g. How come this tone sounds although you don’t keep the key of the small g depressed at all?

In fact the sound of the small g is produced on the string of the capital G! This means that the string does not vibrate in its fundamental vibration but in its first upper vibration, the octave. This works well because the string can vibrate almost as well with two antinodes (bellies) as with one. This is the so-called flageolet-note.

In other words: you have stimulated a harmonic on the string whose frequency is twice the speed of the fundamental frequency of the string. But where did the stimulus for this frequency come from? – It is the capital C string which initiated the overtone. The vibration of this C string contains the small g as a harmonic, namely the second overtone. This second overtone stimulates the (capital) G string to resonate, but not with its fundamental vibration (G), but with its first overtone, the small g, for only this can be stimulated as a harmonic of the (capital) G string. You can hear this tone (g) on the G string as long as you keep the G key depressed.

Table 1: The resonance of the fifth

Thus the resonance of the fifth is generated by the detour of the overtones. Neither string is involved in its fundamental vibration, but both strings are involved through their harmonics. The fact that this works has been demonstrated with the fifth experiment.

The fifth, a simple fraction

In Table 1, the fifth is represented as a fraction: 3/2.

As we have seen, all the tones of a musical scale must be within the range of an octave, i.e. their frequency must be between the single value and the double value of the frequency of the fundamental note. This has been achieved with the frequency ratio of 3/2 = 1.5. We have thus found the first tone within the octave range which has a very simple interval relation to the fundamental note. Whereas the octave vibrates at twice the speed of the fundamental note, the fifth vibrates 3/2 times as fast.

With the exception of the octave, the overtones do not fulfil the conditions for musical scales. Nonetheless, they play a role as transmitters of resonance. We have produced the fifth by simply breaking down the twelfth (the second overtone) by one octave. This breaking down by an octave manifests itself as the 2 in the denominator. The 3 in the numerator is the “inheritance” of the second overtone, the twelfth, which vibrates at three times the rate of the fundamental tone.

Summary

With the fraction of 3/2, which defines the fifth, we have obtained a strikingly simple ratio. This is no accident. We will see how these simple ratios (ideal world!) also play a part for the other notes of a musical scale.

The fact, however, that we are no longer able to use ratios of single integers, like with the overtones, for the musical scales and that instead, fractions (of two integers) are used, is due to the constraint of the octave limitation, which is a constraint of the physical/mental world.

The fifth is not the sole fraction among our musical scale intervals. Integer fractions define the most important tone intervals. We can find them with a simple design rule. On the following page, I will show how this design rule works.


This is a post about the theory of the three worlds.

The overtone series is not a muscal scale

The series of overtones

As we know, the octave is the first overtone. The physical phenomenon of resonance has helped us understand the role played by the overtones: in the physical world, vibrating media such as strings or pipes can vibrate with their basic frequency, but also with an integral multiple of this frequency. In this way the octave results as the first integral multiple of the basic frequency – i.e. by the fact that its frequency is doubled.

It would now be obvious to add the further overtones, which are also integral multiples of the basic frequency, and to explain the single notes of the musical scales in this way.

Fig. 1: The fundamental tone and the first four harmonics

Fig. 1 shows how a string vibrates and how the octave and further overtones are added. Whereas the fundamental tone vibrates with precisely one “belly”, the overtones vibrate with two, three, four and more bellies. If we start with the fundamental tone C, this will result in the following series of overtones:

Fig. 2: Overtone series ranging from the fundamental tone C (note 1) to c“‘ (note 16)

The musical scale works in a closed frequency range

Resonance explains the overtone series, including the octave. How, though, does a musical scale come about, which is meant to fill the narrow range between the fundamental tone and the first overtone, i.e. the octave? As mentioned in the previous post, the notes of the musical scales are subject to this constraint whereby they all have to be within the range of an octave. The overtone series, however, leads far beyond an octave.

In addition, Fig 2 also reveals that the distances between the overtones vary a great deal. Whereas initially, they are very far apart, they get closer and closer as the series proceeds. This would be highly impractical for a musical scale to be applied in reality.

We see, however, that the overtones from note 4 onwards, and even more between notes 8 and 16, constitute something like a kind of major scale: c, d, e, (f), g (a), (h), h, c: nearly our major scale, but not exactly, since the tones in brackets (11, 13, 14) don’t quite fit.

The natural “musical scale” of the alphorn

In fact, the musical scale between notes 8 and 16 corresponds to the natural musical scale of the alphorn – including, however, the “off” notes 11, 13 and 14, and without the actually important fourth, namely the f. Nonetheless, the natural tone series of the alphorn – but also only between notes 8 and 16 – is almost something like a natural musical scale in that it packs a reasonable number of notes into the range of an octave, and this even on the basis of resonance.

Yet the overtone series that can be played on the alphorn is still not a real musical scale. Only the musical scale between notes 8 and 16 can be played on this instrument; most notes of the musical scale below this range are missing while above it, there is a confusing array of many more tones, which are increasingly closer to each other. This is not tantamount to a musical scale which repeats itself octave after octave. Additionally, the instrument is somewhat impractical. In order for the notes to be played at a normal pitch, the horn must of necessity be very long. This is different with a violin or a flute, i.e. substantially more practical. With these smaller instruments, however, we cannot achieve the tones of the musical scale as overtones (which would be flageolet tones with the violin, and with the flute pure overblows like with the alphorn), but by means of deliberate mechanical manipulation of the physical object that vibrates, namely the strings of the violin and the air column of the flute.

But do the overtones and resonances play a role in the musical scales nonetheless? – They do! You can read about this in the next post, which explains how a fifth comes about.

This is a post about the theory of the three worlds.

Real Constraints for Musical Scales

This is a post about the theory of the three worlds and continues the post about the perception of the octave.

Does the coincidence of the three worlds only work for the octave?

The octave demonstrates how mathematics (Platonic world) enters the physical world, and how this convergence of mathematics (integral numbers) and physics (vibrating matters) gives rise to a very special phenomenon, namely resonance. This resonance, in turn, is perceived by us human subjectively (Penrose: mental world) in quite a special way: We subjectively recognise two tones at an octave’s distance from each other as identical tones. Each of us – regardless of our cultural background – perceives a tone with twice the frequency as the “same” tone (Happy Birthday experiment).

If the frequency ratio (mathematics) deviates even only very slightly, the resonance will disappear (physics) and the tones will (mentally) strike us as different, and their simultaneous sound as a dissonance.

The octave as the first overtone thus combines the three worlds. Can we extend this success and use the further overtones following the octave for our musical scale too? The answer to this question is not a simple yes, for the mathematical series of integers has to fit in with the constraints of the physical and mental worlds.

What constraints are these? And what is a musical scale in the first place?

Constraints in the physical and mental worlds

Sounds are used to communicate, and mammals and human beings communicate acoustically. They are able to generate sounds and to hear them. These physical/mental circumstances must be taken into account if we consider how musical scales came into being.

We are unable to produce pitches of any frequency with our voices. And if two tones are far apart from their frequency, we find it difficult to measure their mutual distance (mental, subjective world). Therefore the notes of a musical scale must not be too far apart. This is the first constraint of the physical and mental world in the formation of musical scales.

This physical/mental constraint can be further substantiated and specified: since we perceive a second note an octave higher as the “same” tone (Happy Birthday experiment), a musical scale must not exceed the range of an octave. If it did, the musical scale would overlap with itself because tones outside the octave would immediately find a “same” tone within the octave. For this reason, a musical scale is always limited to the range of an octave, as is the case in all musical cultures.

On the other hand, the notes must not be too close together, for if they were, we would not be able to differentiate between them any longer. A musical scale must therefore not have any number of notes – even though this would be perfectly conceivable in mathematical terms. Yet not everything that is mathematically possible makes sense in reality.

The consequences of these conditions for musical scales can be summarised in two points:

  1. The notes of a musical scale must be inside the range of an octave.
  2. A musical scale must not consist of too many notes.

This is the physical/mental constraint for musical scales.


How can convincing musical scales come into being under these constraints? Can they still be scales with simple mathematical ratios?  →  next post

This is a post about the theory of the three worlds.

The Perception of the Octave in the Mental World

This is a post about the theory of the three worlds and continues the post about the resonance of the octave.

The subjective side

The mathematical world (Pythagoras) with its simple ratios and the physical world with its resonance phenomena provide us with an understanding of the octave but still fail to explain why this interval is the basis of all musical scales in all cultures. To understand this, we will also have to look at the mental world, i.e. the world of our subjective perception.

This world is accessible to everyone, but it will always remain your own and subjective perception. I can’t read your mind. Although imaging techniques such as MRI or PET are capable of observing which areas of the brain are active at what time, what they thus make perceptible is the flow of blood in a specific place, not the thought of how you experience it.

Happy Birthday

The mental world is your very personal world, but it makes quite a contribution to the primacy of the octave. Again, I propose a little experiment, not an objective one as in the preceding post, but still one that is verifiable. It has the advantage that in all likelihood, you will already have conducted it several times.

It can also be a Christmas carol in a family setting. Several people sing together, and if we are lucky, we sing with one voice. At any rate, this is usually our intention. It works better if all the singers have roughly the same register. But what if women and men and children sing together? We still recognise it if they all sing in unison. Although we do not sing in the same frequencies, but with frequencies that are an octave distant from each other, we practically don’t notice it. We perceive the distance of an octave as the same tone. If I, as a bass singing beside an alto, fail to hit the lower octave, I’m out of tune; if I do hit it, I sing in tune. This is the subjective effect of the octave: it is the same note.

The resonance in the physical world facilitates this subjective concurrence of the tones that are an octave distant from each other, and the resonance ratios on the basilar membrane of the inner ear support us in subjectively bringing the two frequencies together in our mental world, too.

First and second overtone

The octave is the first mathematically and physically possible overtone and in this respect it differs from the second overtone, which in the musical scale coincides with a fifth. To illustrate this mathematical correlation, I will again show the vibration ratios of the fundamental tone and the first overtones:

Fig. 1: Octave and fifth as overtones

Why, though, is the octave the characteristic of monophony rather than the fifth, although both of them are most closely related to the fundamental tone in mathematical and physical terms? Although mathematically the fifth is slightly farther distant from the fundamental tone than the octave, the double octave is still farther away, and yet we mentally perceive the double octave as the “same” tone as the fundamental tone, precisely like the octave.

In the mental world, i.e. in what we experience, there is a clear difference between the octave and the fifth. In this world, the octave (and all the multiple octaves) are the “same” tone, whereas the fifth is another tone. This applies all over the world, in all cultures. Since a tone which is an octave higher is perceived as the same tone, the musical scales repeat themselves an octave higher, but not a fifth.

An experiment to distinguish the octave from the fifth in the mental world

The Happy Birthday experiment described above can be extended to demonstrate the difference between the fifth and the octave, as well as the special role of the fifth. At the next birthday party, singers may try, for example, to sing the song not an octave, but a fifth lower (or higher). This is likely to be very difficult for you, precisely because you don’t sing the “same” notes as the others. And if you succeed, the others will look at you in amazement, precisely because you sing the fifth and “not the same tone”. The octave is the same tone, the fifth isn’t.

About access to the mental world

As is well known, the mental world is difficult to prove since it is completely subjective. Although all of us permanently live in this world with our thoughts and feelings, it is only indirectly accessible to objective scientific exploration. You can communicate the contents of your mental experience to other people, but you can never be quite sure that others will experience them in the same way. You can only hope that others will be able to understand your experience. Yet precisely this subjective experience and its comprehension make music so interesting: we share our subjectivity in a very specific way.

Conclusion

We can see how the mathematical, physical and mental worlds precisely meet in the octave. The uniform significance of the octave in all the world’s musical cultures can only be understood when we include all three worlds.


The next post will be about the other notes of the musical scales. Can they also be explained as simply as the octave?

This is a post about the theory of the three worlds.

Resonance and Octave

This is a post about the theory of the three worlds and continues the post about the octave.

We generate a resonance

If you regard resonance as an abstract phenomenon – or as a musical phenomenon that you have not yet experienced – I recommend that you should conduct the following simple experiment: look for a piano (not a digital one) and for a tone on that piano that you can sing well. Press the key of this note and sing it. Of course, this already requires the resonance in your inner ear, otherwise you would not hit the tone. Then press the piano key again, but in such a manner that no sound is produced, and keep the mute key depressed. In this way, the string can vibrate freely. Now sing the tone again. If you have struck the pitch of the key, then the tone will sound in the piano without you pressing the key again. This works best when the piano is open; possibly, you may merely have to sing a bit louder. Now you can sing various tones, for instance a short melody, and you will see that the tone will sound in the piano whenever your voice has the same pitch as the key.

This experiment gives you a sensuous (= physico-mental) impression of the phenomenon of resonance. If you find it difficult to hit the note, there is a simpler way. Depress the piano pedal on the right. Now all the strings can vibrate freely. Now shout at the piano, preferably with the lid open. Again, you will hear how the strings vibrate as an echo of your voice.

Simple resonance

 The “long-distance effect” in the above experiment is not magic but produced by sound waves. These waves resonate with the strings. The typical feature of this is the fact that resonance does not occur with any frequency but precisely when the sound wave hits the string’s natural frequency. Natural frequencies are properties of many physical systems; for example, a bridge can have its natural frequency, as can a glass, a piece of wood or a pot. String and wind instruments are perfected in such a way as to resonate particularly well, i.e. to ensure that their natural frequencies are particularly strong and sonorous.

Higher-level resonances

 Again I propose a small experiment, and again you will need a piano, which should be tuned this time.

Fig. 1: Two Cs on the piano at the distance of an octave

 Now depress the higher C key on the piano (the one on the right). Of course there are many such Cs on the piano; it would be best to take two neighbouring Cs in the middle of the keyboard, where the experiment can be heard most clearly. You can also take tones other than C; the experiment works with all tones, provided that the distance between the two tones is precisely an octave. You will now also realise why the octave is so called: the higher C is at a distance of eight (Latin octo) tones from the lower one (when you count the musical intervals, the starting tone is always counted as well).

Now keep the higher (right-hand) C key mutely depressed. Now hit the lower C key briefly and strongly. You will again hear a “long-distance effect”. Clearly, the string of the higher C started to vibrate when you hit the lower C. Now hit the keys immediately to the right and left of the lower C. You will not be able to get the higher C to vibrate with those keys; no resonance occurs.

Why resonance occurs precisely with an octave

 Fig. 2:  Possible vibrations of a string

In Fig. 2, you can see five possible vibration patterns for a stretched string. At the bottom (at 1), the string vibrates with precisely one wave peak. At 2, there are two peaks; at 5, there are five. Yellow represents the vibrating string; the black line shows the corresponding sound wave, i.e. the travelling sound wave which has the same frequency as the standing wave, which is represented by the resonant string.

State 1 in Figure 2 is the basic state, i. e. the tone which you hear when you press the piano key. State 2 is the next permitted state of the vibration. Here, the string vibrates with two peaks; at 3, there are three, etc. All states in which the string at its two fixed ends does not vibrate are states that permit the string to vibrate unimpeded. Thus it is not only the state of simple string vibration that is possible, but in principle every state that corresponds to a wavelength that fits integrally into the string length.

In state 2, the wavelength is half as long as in the basic state and thus the frequency is twice as fast/high. State 2, with its frequency twice as high, corresponds to the tone that sounds an octave higher; state 4 corresponds to the tone that sounds two octaves higher.

Now why does the higher C also resonate when you hit the lower C as in the experiment proposed above? The reason for this is the fact that the string of the lower C – like any other string – does not only generate sound in the basic state (state 1 in Fig. 2), but more or less in all the permitted vibrations. These vibrations are thus superimposed on each other. When the sound waves emitted from the lower string reach the string of the higher C, then they do not only contain the basic vibration, but a bit more faintly also the higher vibrations and therefore precisely also the vibration of the higher C string. Thus a resonance is generated.

Sine vibrations and overtones

 In mathematical terms, the two black curves in Fig. 2 are sine curves. With a technical device, it is possible to generate such curves acoustically; we then speak of a sine vibration. In natural resonating bodies such as piano strings, the human voice or everywhere else in nature, such pure sine vibrations do not exist; rather, the sound waves produced by them always also contain higher vibrations (levels 2ff. in Fig. 2) in complex superimpositions. They are called overtones. The proportions of the individual overtones, i.e. the extent to which the vibrations of levels 2ff. resonate besides the fundamental tones in the sound mixture, are highly variable and are determined by the sound-producing medium. These mixtures account for the character of the sound of the individual instrument.

Interpretation of the string vibrations in the three worlds

Platonic → physical (from simple to complex)

 The example of the vibrating string shows us how mathematical laws from the Platonic world determine the physical world. In the physical world, however, they manifest themselves in many different ways, and a great diversity emerges: several vibrations are simultaneously generated on the string; besides the fundamental tone, there are always many overtones at the same time. Each single one of these vibrations can be described very simply in mathematical terms. The mixture, however, is very complex.

What is very simple in the mathematical world, i.e. in the Platonic world, quickly becomes complex as soon as it takes effect in the physical world.

Penrose’s endless staircase and the “anti-Penrose” direction

In my view, the funnels in Penrose’s sketch represent only one direction of the relationships. Penrose emphasises in his explanation that a description of physics does not require the whole of mathematics and thus arrives at proportions such as those represented in the sketch with the funnels and which appear to contradict logic as in the endless staircase.

In my view, however, the funnels can also be seen in the opposite direction when we focus on the volume of information. This is larger in the physical world than in the Platonic one. When mathematics enters physics, new things emerge, namely the complex diversity of the mixing ratios. This concrete diversity in the physical world constitutes a piece of information which far exceeds the information of the original mathematical world. The volume of information increases in the direction from Platonic to physical. In terms of volume, this represents a countermovement to Penrose’s funnel. Thus when we take a closer look, the endless staircase of the three worlds loses some of its paradoxical terror.

Platonic → mental 

Presumably you have heard technically generated sine vibrations. They were the beginning of electronic music and had the charm of something new and technical at the time. It was precisely their naked purity that was impressive. However, these tones also become very boring very quickly. The purity and the sterile banality of these technical sounds is caused by the lacking resonance of the overtones. As listeners, we perceive the rich information of these additional vibrations, and they account for the wealth of natural sounds. I wouldn’t want to have to do without them.

In the next post, I would like to explain why the octave is so important in the mental world and what contributes to the fact that musical scales in all cultures are always based on the octave.


This is a post about the theory of the three worlds.

The Octave

A remarkable common feature

All the musical scales known to me encompass an octave. Even scales which tones unusual to us Europeans – Arabic, Indian, Japanese and African ones – encompass precisely an octave, i.e. the deepest and highest tones have a distance of precisely an octave, whatever scale this may be.

I find this extremely remarkable. This is as if all the world’s languages, which after all have very different words, used the same word for a certain concept, had always done so, and done so independently of each other. What is the reason for this?

The theory of the three worlds is capable of providing a plausible explanation of the unusual common feature of the musical scales of all human cultures.

The octave in Platonic terms

 If you pluck a string on a violin, you will produce a tone. If you press a finger onto the fingerboard exactly in the middle of the string, the tone will be one octave higher. The same applies to pipes. A pipe that is half as long as another one sounds an octave higher. Obviously, the octave is based on a ratio of 1:2. This is the Platonic, i.e. mathematical side of the octave. Simple mathematical ratios (= fractions) also play a part in connection with other intervals, which will be discussed later.

These mathematical ratios of the relationships between the tones – i.e. the intervals – have long been known and were taught by the Greek Pythagoras, who founded an influential school in southern Italy before Socrates and Plato.

Fig. 1: A vibrating string. In the upper graph, the string is attached on the left and on the right (0 and 1) and is consequently incapable of vibrating there. The farther away it is from the attachment points, the more strongly it vibrates, most strongly in the middle. In the lower graph, a finger has been pressed onto the string, and it now vibrates in half its length and an octave higher. (With these descriptions, however, we have already left the Platonic world and entered the physical world.)

The simple ratio doesn’t yet explain the uniqueness of the common feature, the octave, across all human cultures. Why does the ratio play a part in musical scales at all?

To explain this, we’ll have to have a look at the other two worlds, namely the physical, in which the tones are produced, and the mental, in which we perceive them.

The octave in physical terms

 Tones

Tones are material vibrations in a transmission medium such as air. As a rule, a tone contains a superimposition of several vibrations (fundamental tone plus overtones). At this moment, however, we are only looking at the fundamental vibration, which determines the recognisable pitch.

This fundamental vibration is a sine wave, and the pitch is indicated as a frequency, for instance 440 Hz. This frequency means that the sine wave vibrates at a rate of 440 movements per second. The same is done by the string.

When the string vibrates in a fixed place, we speak of a standing wave (cf. Fig. 1 above). Conversely, the vibration in the air moves away from this fixed place (travelling wave). The string is able to move the air by means of its stationary vibration and thus produces a vibration in the air, a sound wave. The string transmits the properties of its vibration, particularly its frequency, to the sound wave.

The wavelength in a travelling wave, i.e. a sound wave, but also a wave on a water surface, for example, is the distance between the antinodes (or wave peaks). In a standing wave such as the string in Fig. 1, the wavelength equals the (double) length of the vibrating string.

If the speed of a travelling wave is constant, then more antinodes must follow each other, the shorter the distances between them are. The distances between the wave peaks represent the wavelength, the number of peaks per time unit represent the frequency of the wave. The more peaks pass a specific place, the smaller their distances.

Thus there is an inversely proportionate ratio between wavelength and frequency, i.e. the shorter the wavelength, the higher the frequency must be. This is why the string that is half as long vibrates at twice the speed. This is the physical origin of the octave.

Tone generation

How does the vibration get into the string? This is the consequence of the fact that a stretched string has a tendency towards natural oscillation. The tension in the string leads to a situation whereby a stimulus, for instance the plucking of a string, triggers off a movement which does not stop at either end of the string but is pushed back. In this way, the standing wave is produced. The wavelength, i.e. the distance between the antinodes, is determined by the length of the string. The reason for this is the fact that no motion is possible any longer at either end of the string since it is attached there. The wave can only vibrate in between. The wavelength must therefore fit precisely into the length of the string. 

The octave in mental terms

The inner ear

 We perceive sound with our two inner ears. These are organs of an extremely refined design with the structure of a snail, which is why they are called cochlea (Greek for snail). The sound wave comes from outside and travels into the cochlea, which is filled with liquid, and by means of resonance generates a vibration in the so-called basilar membrane, which runs through the entire cochlea. Along the basilar membrane, so-called hair cells receive the vibrations of the basilar membrane and transmit them into the brain as electrical signals. The complex and refined structure of the cochlea, which is only cursorily described here, enables the acoustic signals to be analytically separated so that depending on the frequency, different hair cells are stimulated: the higher the frequency, the closer to the entrance of the cochlea; the lower the frequency, the deeper inside the cochlea.

 Mental tone perception

 Up to this point, tone perception through the inner ear has nothing to do with the mental world as yet; these are merely the anatomical requirements, i.e.  the physical apparatus which specifically prepares the physical signals (the sound waves) for actual perception. This latter takes place in the brain and is a subjective process.

Subjective processes are characterised by the fact that they cannot be understood from the outside. I don’t know how you hear or feel something; this is entirely your own world. However, we have so many common properties as human beings that I may assume that you will experience many things very similarly to me. We have the same anatomy and the same living conditions. Why do many people perceive the same music as beautiful? If we are moved by the same music and apprehend it as cheerful, sad, comforting, rousing, etc. like other people, this demonstrates that our mental worlds are strongly connected to each other despite their subjectivity.

In this context, cultural aspects – learned habits – play a very important role. Ultimately, culture is also part of the mental world; it is the spirit, i.e. the subjectivity, that we share.

This individual and collective subjectivity, our mental world, is not least also based on the physical preconditions, i.e. the physical world.

Thus we are back with our topic: why do all human cultures have the octave in their musical scales, which are so different in other respects? The reason for this can now be explained in terms of physics and lies in resonance.

Resonance

 Resonance is required for tones to arrive in the inner ear at all, for the basilar membrane in the inner ear receives the vibrations of the sound waves in a very specific manner. Not all the frequencies find the same resonance in the basilar membrane. The inner ear is structured in such a way that the basilar membrane resonates with high frequencies at its entry and with low frequencies in its depth. In this way, the ear analyses the various pitches. But resonance is responsible for much more, inter alia also for the fact that the octave is always present in the thousands of different musical scales.

This conspicuous observation will be the subject of the next post.

In a further post, I will then deal with the perception of the octave in the mental world, i.e. our subjective world.


This is a post about the theory of the three worlds.

The next post will deal with resonance in the three worlds.


Translation: Tony Häfliger and Vivien Blandford

The bit has no meaning

The bit is the basis of IT

Our information technology is based on the bit. Everything that happens in our computers is based on this smallest basic element of information. If someone asks you what a single bit means, you may well answer that the bit can assume two states, of which one means 0 and the other means 1. As is generally known, this enables us to write numbers of any size; all we have to do is to line up a sufficient number of bits.

But is this really true? Does the one state in the bit really mean 0 and the other 1? Can these two states not also assume completely different meanings?

A bit can be attributed arbitrary meanings

In fact, the two states of the bit can assume any meaning. Besides 0/1, true/false, yes/no and positive/negative are also popular; but in principle and in practice, a bit can be attributed any meanings from the outside. Of course, inversions are also possible, i.e. 0/1 and 1/0.

The attribution of the meaning of the bit comes from the outside

Whether the specific bit in the computer programme means 0/1 or 1/0 or something else, does of course play a crucial part. However, the meaning is not in the bit itself, for the bit is a most radical abstraction. It only says that two states exist and which is currently active. What the two mean, however, is a completely different story, which goes far beyond the single bit. In a computer program, it can be declared, for instance, that the bit corresponds to the TRUE/FALSE pair of values; but the same bit, together with another bit, can also be interpreted as part of a number or a letter code – very different meanings, then, depending on the program context.

Digital and analogue context

The software program is the digital context, and of course it consists of further bits. The bits from the surroundings can be used to determine the meaning of a bit. Let’s assume that our bit and other bits are involved in defining the letter ‘f’. Our program is also organised in such a manner that this letter will appear in a table, in a column which is headed ‘Gender’. All this is clearly set out in the software. Now, does the software determine the meaning of the bit? You will doubtless not be surprised if the ‘f’ means ‘female” and the table probably lists various people who can be male (m) or female (f). But what do male and female mean? It is only in the analogue world that these expressions receive a meaning.

The bit, the perfect abstraction

In fact, the bit represents the final point of a radical abstraction of information. In a single bit, information is reduced to what is absolutely elementary in that the information about the meaning has been completely removed from the bit. The bit merely says that two states exist that have been described outside it and which of the two is active at a specific point in time.

This radical abstraction is intentional and makes a great deal of sense in a software, for in this way, the same physical bit in the chip of the computer can be put to a new use again and again, once as a TRUE/FALSE pair, once as 0/1, once as YES/NO, etc. This is very practical and enables the computer to solve any task whatsoever. The perfect abstraction that has thus been achieved, however, simultaneously deprives the single bit of its individual meaning, which can and must be attributed to it anew for every application.

The endless regress

When the meaning of the bit is given from the outside, then of course other bits can take on this task and define the meaning of a bit. For this purpose, however, these outside bits must have the necessary effective power, which of course they cannot have without their own meaning. And naturally, the meanings of the bits of this outer circle are not in these bits themselves – for the same reason as above – but have to be given from the outside, i.e. by a further circle of bits. The bits of this second outer circle must be explained in a further circle, and the meanings of the bits of this further circle in another outer circle… Of course this process of attributing meanings never reaches an end in a world of bits: the regress is endless.

The endless regress only ends in the analogue world

Only when we step out of the program into the real world are we really able to attribute a meaning to the information from the computer.

Selective and descriptive information content

If we recapitulate the above, we can make the following distinction in the bit:

The descriptive information content says what the bit means; it describes the two states of the bit but does not say which state has currently been selected. The selective information content says which of the two states is currently active but does not know anything about the properties of the two states and thus about their individual meanings.

The distinction between the selective and descriptive information content was coined by the British radar pioneer and information scientist Donald McKay in the 1940s, practically at the same time as the first mention and description of the classic bit by the American Shannon. McKay also clearly recognised that Shannon’s bit only carries a selective information content and that the descriptive information content must be given from the outside.

Surprisingly, this insight of McKay’s has almost fallen into oblivion today.

Conclusion:

  1. The bit supplies the selective information content.
    2. The descriptive information content is not located in the bit.
    3. Thus the bit on its own does not have any meaning.
    4. The meaning of the bit is always given from the outside.
    5. This initiates an endless regress.
    6. Only in the analogue world does the endless regress end.

Musical Scales in the Theory of the Three Worlds

Scales are patterns

When you hear a melody, it is based on a musical scale, i.e. a number of a few distinct notes which may occur in the melody. In a linear sequence, these tones constitute the scale. Most melodies that can be heard in our cultural area can be traced back to one single scale, the Ionian or major scale, which is made up of seven notes in very specific scale steps.

Thousands of scales

However, there are thousands of different scales. Presumably you are familiar with the minor as well as with major scale and may have heard something about pentatonic scales or about whole tone scales, Lydian and Phrygian scales, Indian ragas, Japanese and African scales. All these scales differ from each other.

As we will see, however, they have some astounding similarities. Why should people all over the world, in all cultures and with all their differences, comply voluntarily and strictly with these similarities? The reasons for this are easy to explain if we don’t merely look at one world, but at the interaction of all three worlds.

In which of the three worlds do the scales exist?

Scales are part of our reality, no matter how we define reality – unless we define reality as that which we call matter. In that case, the scales are not part of matter. They may manifest themselves in the physical world, for instance if a human being sings or plays them, but they have an identity which is independent of the individual way they are performed. In this sense, scales are non-local, as is typically the case with entities of the Platonic world. Between the scale and its performance, there is thus the relationship of an abstract, i.e. Platonic pattern with its material instance. This is always a 1/n relationship, for the pattern is unique but can be the source of any number of instances.

As a pattern, scales are part of the Platonic world, even though they manifest themselves in the material world. Mathematics, in particular, has much to do with the form of scales, which can be demonstrated easily, yet you don’t need to know anything at all about this kind of mathematics in order to recognise the scales correctly or to sing them. Your mental world in which you experience these scales has no need of figures and formulae.

Scales thus exist in all three worlds:

Platonic world: here, a scale exists as an entity, i.e. as a unity and as a whole. Here, every scale exists only once.

Physical world: here, a scale exists as any number of occurrences – whenever melodies are produced on the basis of it.

Mental world: here, i.e. in your head, you recognise the melodies and the scales.

Of course, each world is organised in its very own way. Now, how do the three worlds interact?


This is a text in the series about the theory of the three worlds.

Translation: Tony Häfliger and Vivien Blandford

The Physical World

The world of the natural sciences

The physical world is what is explored by the natural sciences and by physics in particular. The successes of the natural science programme are obvious, both with regard to its insights into how the world works, i.e. theory, and with regard to the technologies this enables, i.e. practice. The natural sciences have changed our world fundamentally ever since Galileo Galilei.

Objectivity

The success became possible because from the Renaissance onwards, the thinkers and explorers in Europe did not solely refer to what had been handed down since ancient times, but conducted unprejudiced research and looked for results themselves. Whereas the monks in the monasteries interpreted and compiled old manuscripts (scholasticism), the free spirits dared to believe what they themselves could see in nature – even if it was in contradiction to the monastic authorities.

However, the loss of the old authorities called for a new guiding principle to prevent a situation whereby everyone would be able to claim anything. Therefore researcher’s proposition should be independently verifiable, and solely what was discernible by everybody beyond any doubt should in future be true and applicable. Thus the ideal of objectivity was born.

Measurability

But the world should not only be able to be described objectively, but also measured with the highest possible precision. This has two advantages: a) A proposition is all the more credible the more precise its predictions are. The more precisely we are able to measure things, the more significant the observations. b) Besides more precise insights, precise measurements also enable us to build increasingly precise instruments and machines.

The world from the outside

The natural sciences thus focus on what can be seen and measured from the outside. This is what Penrose describes as the physical world. Not my internal view, my feeling or my belief is what is called for, but what can be observed and measured from the outside beyond any doubt. This is the physical world.

The physical world in interaction

We could consider the physical world to be the sole true reality, but our view of the world becomes more inclusive if we add the other two worlds. How do the three worlds interact? – There are bridges from one to the other, there are crossovers, and there are effects from one world on the others. I would like to illustrate how these interactions work with examples from the field of music – a field in which obviously all three worlds are involved.


This is a text in the series about the theory of the three worlds.

Translation: Tony Häfliger and Vivien Blandford


 

The Platonic world

Why “Platonic”?

Penrose calls one of the three worlds in the theory of three worlds as Platonic. Why?

Plato

The rich Athenian citizen Plato was a follower of the philosopher Socrates. He set up a school of philosophy in the 4th century B.C., which was fundamental for European philosophy and has crucially shaped philosophical discussions until the present day. If Roger Penrose thus calls one of the three worlds “Platonic”, he refers to Plato and specifically to one particular question and the discourse about it, which is still of great significance today. This question is, “Are ideas real?”

Plato’s realism of ideas

Subsequent philosophers often presented the issue as a conflict between Plato and his disciple Aristotle. Plato is ascribed the attitude that ideas were not only real but even constitute actual reality, while what we describe as reality were mere shadows of the original ideas. Penrose calls the abstract world of mathematics “Platonic”, thus referring to Plato’s thought that abstract ideas had the quality of reality.

The world of ideas as one of the three worlds

Of course the Platonic reality of ideas was also disputed, and Europe’s history of philosophy is full of pros and cons about it, which under the headings of realism, nominalism and the problem of universals have shaped the philosophers’ discourse for many centuries and exert an influence in the background even now. Like Plato, Penrose’s theory attributes a reality to the abstract Platonic world, but not an exclusive reality, as would an uncompromising Platonic realism, but as one of the three real worlds, which interact with each other. Thus the theory of the three worlds is not about which world is the real and true one – which was discussed at length as the problem of universals – but about how the interaction takes place between them.

But let’s return to the Platonic world. What distinguishes it from the other two worlds?

Characteristics of the Platonic world

 Nonlocality

Where is the number “3”? Can you point your finger at it somewhere in your environment?

Of course you can point at three apples, at three pencilled lines or at three coffee cups, but this is not the number three; rather, they are apples, pencilled lines and coffee cups. The number three remains abstract. No one can point at it.

Naturally, you can also point at the word “three” or at the “3” in this text, but these are only symbols of the number and not the number itself. The number itself remains abstract; it simultaneously exists everywhere and nowhere.

Symbols are always in a certain place, they are thus localised. The number itself, however, is non-local, i.e. there is no place in the universe wh  ere the number is found; rather, it can be found everywhere. It exists on earth, on the moon and equally in Andromeda. This nonlocality is a very elementary property of the objects of the Platonic world; in particular, it distinguishes them from the objects in the physical world, in which objects are locally defined, i.e. localised.

Timelessness

 The Platonic world’s relationship with time is analogous to locality:

1 plus 2 is 3 – this is true now, was true yesterday and will be true tomorrow and for ever thereafter. In this sense, we can describe the Platonic world as a place of eternal truths, in stark contrast to the physical world, which is subject to constant change. If it rains today, the sun may shine tomorrow; 1 plus 2 is 3 every day and any day. This timelessness applies to all mathematical statements, but also to their objects, again in contrast to the objects of the physical world: the number 3 is timeless, whereas 3 apples are not.


This is a text in the series about the theory of the three worlds

Semantics

What is semantics?

A simple and easily understandable answer is that semantics is the meaning of signals. The signals can exist in any form: as text, as an image, etc. The most frequently studied semantics is that of words.

This is a good reason to examine the relationship of linguistics and semantics. Can semantics be regarded as a subdiscipline of linguistics?

Linguistics and semantics

Linguistics, the science of language and languages, has always examined the structure (grammar, syntax) of languages. Once the syntax of a sentence has been understood, linguists see two further tasks, i.e. secondly to examine the semantics of the sentence and thirdly to examine its pragmatics. “Semantics” is about the meaning of sentences, “pragmatics” about the “why” of a statement.

The linguists’ three steps

In the linguists’ eyes, there are thus three steps in understanding language: syntax -> semantics -> pragmatics. These three fields are weighted very differently by linguists: a conventional textbook predominantly deals with syntax, whereas semantics and pragmatics play a marginal role – and always on the basis of the previously conducted syntactic analysis. The linguists’ syntactic analysis thus already sets the course for what is based on it, namely semantics and pragmatics.

This is not really ideal for semantics. When you deal with semantics in more detail, it becomes clear that the grammar and other properties of individual languages constitute externals which may circumscribe the core of the statements – their meaning – in an occasionally very elegant manner, but they merely circumscribe them and do not represent them completely, let alone directly. A direct formal representation of what is meant by a text, however, would be the actual objective of a scientific semantics.

Can this objective be attained? First, we will have to clarify the relationship between words and concepts – words and concepts are not the same. Concepts are the basic elements of semantics and have a special, but not entirely simple relationship with the words of a language.

Word does not equal concept

One could flippantly assume that there is a one-to-one relationship between words and concepts, i.e. that behind every word, there is a concept which summarises the meaning of the word. But this is precisely what is wrong. Words and concepts cannot unequivocally be mapped on each other. The fact that this is the case can be recognised by everybody who observes himself while reading, talking and thinking.

It is obvious that a word can have several meanings depending on the context in which it is uttered. Occasionally, a word may even have no meaning at all, for instance if it is a technical term and I don’t know the specialist field. In such a case, I may be able to utter the word, but it remains devoid of meaning for me. Yet somebody who understands the specialist field will understand it.

Meaning has much to do with the addressee

Even perfectly normal words which we all know, not always have an unequivocal meaning but can evoke slightly different ideas (meanings) depending on the listener or the context. This does not only concern abstract words or words to which various values are attached, such as happiness, democracy, truth, etc.: absolutely concrete terms like leg, house and dog are interpreted differently by different people, too. The reception of the words as meaningful concepts has much to do with the addressee, his situation and expectations. There is definitely no 1:1 relation between words and concepts.

Meanings vary

Even in ourselves, there are quite different ideas for the same word; depending on the situation, we associate different ideas with the same word, depending on the situation and the everchanging state of our momentary knowledge of words and topics.

A dynamic process

The transition from one language to another shows how the link between words and concepts is a dynamic process in time and changes the meaning of the words. The English word ‘brave’ is the same word as the word ‘bravo’ in Italian, which we use if a musical performance inspires us. But the same word also exists in German, where today it means prissy or well-behaved – certainly not exactly the same as brave, though it is the same word and once meant the same in German as in English.

Semantics examines the play of meanings

We have to accept that a word and a concept cannot be mapped on each other just like that. Although in individual cases it may seem that there is precisely one concept (one semantics) behind every word, this idea is completely inappropriate in reality. And it is this idea which prevents the play of meanings from being understood correctly. Yet it is precisely this play of meanings which, in my view, constitutes semantics as a field of knowledge. In this field, it is possible to represent concepts formally in their own proper structure – which is completely independent from the formal representation of words.


Translation: Tony Häfliger and Vivien Blandford

The theory of the three worlds (Penrose)

The theory of the three worlds

There are practical questions which concern our specific lives, and there are theoretical questions which seemingly don’t. However, there are also theoretical considerations which definitely concern our practical everyday lives. One of these is the three worlds theory, which deals with questions as to which worlds we specifically live in.

On what foundation is our everyday existence based? The theory of the three worlds points to the fact that we simultaneously live in three completely different worlds. Practically, this does not constitute a problem for us; theoretically, however, the question arises as to how three worlds which are so different from each other are able to meet in reality at all.

Roger Penrose has named the three worlds as follows:
A) the Platonic world,
B) the physical world,
C) the mental world.

This is Roger Penrose’s original graph:

 

 

 

 

 

 

 

 

Platonic world: The world of ideas. Mathematics, for example, is completely located in the Platonic world.

Physical world: The real, physical world with things that are in a specific place at a specific time.

 Mental world: My subjective perceptions without which I would not be able to recognise the other worlds, but also my thoughts and ideas as I experience them.

The circular relationship between the three worlds

The arrows between the spheres indicate the circular relationship that these worlds engage in together:

Platonic → physical: Behind physics, there is mathematics. Physics is inconceivable without higher mathematics. Evidently, the physical world complies with mathematical laws with a staggeringly accurate precision. Is the real world therefore determined by mathematics?

 Physical → mental: My brain is part of the physical world. According to common understanding, the neurons of the brain tissue determine my brain performance with their electric switches.

 Mental → Platonic: Great thinkers are capable of formulating the laws of mathematics in their thoughts (mental world); these laws “come into being” in their heads.

This, then, is the circular process: The Platonic world (mathematics) determines the physical one, which is the basis of human thought. In human thought, in turn, mathematics (and other ideas) are located. These mathematical laws … and here we come full circle.

The scope of the three worlds

What is also interesting are the opening funnels in Penrose’s sketch, which together with the arrows point from one world to the next. Penrose uses them to indicate the fact that the world that follows in the circular process merely requires part of the world from which it emerges during the generation process.

Platonic → physical: Only a small part of mathematical findings can be used in physics. Seen in this light, the physical laws only need (are?) an excerpt from mathematics.

Physical → mental: My brain is a very small part of the physical world.

Mental → Platonic: My brain deals with many things; mathematics and abstract ideas are only a part of it.

The Platonic world is then the origin of the physical world again. However, the proportions do not appear to work out properly. This resembles the famous impossible staircase:

figure: the impossible staircase

The impossible staircase

As an aside:
The impossible staircase was discovered by Roger Penrose’s father, Lionel Penrose, and is also called the Penrose steps – or the Escher-Penrose steps after the Dutch graphic artist who, inter alia, inspired Douglas Hofstadter to write his book Gödel, Escher, Bach. The endlessness with which the steps ascend can seemingly be graphically represented without any problems, but from a logical point of view it is eminently intricate (self-referential taboo).

For Penrose, there is a mystery in the three worlds. He writes that undoubtedly there are not three separate worlds in reality but only one, and at present we are not even able to divine the true nature of this world. This is therefore about three worlds in one – and thus about their differences and the form of their interlinkage.

Not an abstract theory

The three worlds are not an abstract theory but can be recognised in our own world of private experiences. They play an important part in music, for instance. The example of music also enables us to see how the three worlds interact. More about this on this website.


Translation: Tony Häfliger and Vivien Blandford

Artificial and natural intelligence: the difference

What is real intelligence? 

Paradoxically, the success of artificial intelligence helps us to identify essential conditions of real intelligence. If we accept that artificial intelligence has its limits and, in comparison with real intelligence, reveals clearly discernible flaws – which is precisely what we recognised and described in previous blog posts – then these descriptions do not only show what artificial intelligence lacks, but also where real intelligence is ahead of artificial intelligence. Thus we learn something crucial about natural intelligence.

What have we recognised? What are the essential differences? In my view, there are two properties which distinguish real intelligence from artificial intelligence. Real intelligence

– also works in open systems and

– is characterised by a conscious intention.

 

Chess and Go are closed systems

In the blog post on cards and chess, we examined the paradox that a game of cards appears to require less intelligence from us humans than chess, whereas it is precisely the other way round for artificial intelligence. In chess and Go, the computer beats us; at cards, however, we are definitely in with a chance.

Why is this the case? – The reason is the closed nature of chess, which means that nothing happens that is not provided for. All the rules are clearly defined. The number of fields and pieces, the starting positions and the way in which the pieces may move, who plays when and who has won at what time and for what reasons: all this is unequivocally set down. And all the rules are explicit; whatever is not defined does not play a part: what the king looks like, for instance. The only important thing is that there is a king and that, in order to win the game, his opponent has to checkmate him. In an emergency, a scrap of paper with a “K” on it is enough to symbolise the king.

Such closed systems can be described with mathematical clarity, and they are deterministic. Of course, intelligence is required to win them, but this intelligence may be completely mechanical – that is, artificial intelligence.

Pattern recognition: open or closed system?

This looks different in the case of pattern recognition where, for example, certain objects and their properties have to be identified on images. Here, the system is basically open, for it is not only possible that images with completely new properties can be introduced from the outside. In addition, the decisive properties themselves that have to be recognised can vary. The matter is thus not as simple, clearly defined and closed as in chess and Go. Is it a closed system, then?

No, it isn’t. Whereas in chess, the rules place a conclusive boundary around the options and objectives, such a safety fence must be actively placed around pattern recognition. The purpose of this is to organise the diversity of the patterns in a clear order. This can only be done by human beings. They assess the learning corpus, which includes as many pattern examples as possible, and allocate each example to the appropriate category. This assessed learning corpus then assumes the role of the rules of chess and determines how new input will be interpreted. In other words: the assessed learning corpus contains the relevant knowledge, i.e. the rules according to which previously unknown input is interpreted. It corresponds to the rules of chess.

The AI system for pattern recognition is thus open as long as the learning corpus has not been integrated; with the assessed corpus, however, such a system becomes closed. In the same way that the chess program is set clear limits by the rules, expert assessment provides the clear-cut corset which ultimately defines the outcome in a deterministic way. As soon as the assessment has been made, a second and purely mechanical intelligence is capable of optimising the behaviour within the defined limits – and ultimately to a degree of perfection which I as a human being will never be able to achieve.

Who, though, specifies the content of the learning corpus which turns the pattern recognition program into a technically closed system? It is always human experts who assess the pattern inputs und who thus direct the future interpretation done by the AI system. In this way pattern recognition can be turned into a closed task like a game of chess or go which can be solved by a mechanical algorithm.

In both cases – in the initially closed game program (chess and Go) as well as in the subsequently closed pattern recognition program – the algorithm finds a closed situation, and this is the prerequisite for an artificial, i.e. mechanical intelligence to be able to work.

Conclusion 1:
AI algorithms can only work in closed spaces.

In the case of pattern recognition, the human-made learning corpus provides this closed space.

Conclusion 2:
Real intelligence also works in open situations.

Is there any intelligence without intention?

Why is artificial intelligence unable to work in an open space without assessments introduced from outside? Because it is only the assessments introduced from outside that make the results of intelligence possible. And assessments cannot be provided purely mechanically by the AI but are always linked to the assessors’ views and intentions.

Besides the differentiation between open and closed systems, our analysis of AI systems shows us still more about real intelligence, for artificial and natural intelligence also differ from each other with regard to the extent to which individual intentions play a part in their decision-making.

In chess programs, the objective is clear: to checkmate the opponent’s king. The objective which determines the assessment of the moves, namely the intention to win, does not have to be laboriously recognised by the program itself but is intrinsically given.

With pattern recognition, too, the role of the assessment intention is crucial, for what kind of patterns should be distinguished in the first place? Foreign tanks versus our own tanks? Wheeled tanks versus tracked tanks? Operational ones versus damaged ones? All these distinctions make sense, but the AI must be set, and adjusted to, a specific objective, a specific intention. Once the corpus has been assessed in a certain direction, it is impossible to suddenly derive a different property from it.

As in the chess program, the artificial intelligence is not capable of finding the objective on its own: in the chess program, the objective (checkmate) is self-evident; in pattern recognition, the assessors involved must agree on the objective (foreign/own tanks, wheeled/tracked tanks) in advance. In both cases, the objective and the intention come from the outside.

Conversely, natural intelligence has to determine itself what is important and what is unimportant, and what objectives it pursues. In my view, an active intention is an indispensable property of natural intelligence and cannot be created artificially.

Conclusion 3:
In contrast to artificial intelligence, natural intelligence is characterised by the fact that it is able to judge, and deliberately orient, its own intentions.


This is a blog post about artificial intelligence. You can find further posts through the overview page about AI.


Translation: Tony Häfliger and Vivien Blandford