Extra Chapter II

Variable Qualia

When one looks at a house, listens to a song, or smells a flower, an image quale of the house, a sound quale of the song, or an odor quale of the flower appears in one’s mind. Because these qualia seem unique and fascinating, some people wonder whether others experience them similarly or differently from how they do. For example, please see Figure II.1. When people look at the same color C, is it the case that the color C qualia appear as red in some people but as blue, green, or other colors in others? Moreover, is it possible that, in some people, the color C qualia appear as some extraordinary colors that are not in the normal color spectrum that general people perceive (so the colors cannot be shown here, or even in any other pictures), such as the color represented by “!” in the figure?

Variable qualia

Figure II.1 Variable color qualia among people

Despite these strange possibilities, all people will call what they see in their minds the same, “color C,” even though the manifestations of the color qualia in their minds are different (red, blue, green, etc.). Even more bizarre possibilities are that the color C qualia may appear in some people as other kinds of qualia, such as the auditory quale, olfactory quale, or the quale of an unusual percept that occurs only in some people instead of the color quale. Remarkably, despite these differences, all of them will still call what they experience in their minds the same, “color C”!

Although philosophers have long presented and discussed this puzzle [1–3], it remains unresolved. Therefore, this chapter attempts to find solutions based on scientific evidence. It finds that there are several variations of this puzzle and that some of them have definite answers.

Variable Qualia

In this theory, qualia that manifest themselves variably, that is, manifest themselves differently in the minds of different people even though they are qualia of the same thing, are called variable qualia. Hypothetically, there can be various types of variable qualia, not just the type in the example above. Based on the causes of variability (physical vs. non-physical) and how variability occurs (randomly vs. restrictedly and completely vs. partially), they can be classified as follows:

II.1 Physically originated variable qualia
II.2 Non-physically originated variable qualia
II.2.1 Randomly variable qualia (RVQ)
• II.2.1.1 Randomly variable qualia-complete (RVQc)
• II.2.1.2 Randomly variable qualia-partial (RVQp)
II.2.2 Restrictedly variable qualia
• II.2.2.1 Inverted qualia
• II.2.2.2 Shifted qualia
• II.2.2.3 Identical-structure qualia

Now, let us investigate them to see which one(s) can really occur and which one(s) cannot.

II.1 Physically Originated Variable Qualia

Physically originated variable qualia are qualia that are variable and appear differently among people because of physical causes.

Variability in qualia of this kind occurs because many physical factors that are involved in the processes of perception and affect the perception of neural processes, associated mental processes, and associated qualia, such as environmental, anatomical, and physiological factors, are different among individuals. For example, in the case of perceiving a color, the environmental factors, such as the illuminating light, the light’s angle of incidence, the light’s angle of reflection, and the intervening medium (e.g., air, water, and glass) between the color and the observer’s eyes, and the anatomy and physiology of the whole visual perception pathway, from the corneas of the eyes to the neural circuits for visual perception, differ among people. Consequently, the resulting neural processes’ and mental processes’ perceptions and the associated perception qualia (which, according to Theorem IV, are the signaling patterns of neural processes) will be different. Thus, it is highly likely that different people will consciously experience (mentally see) the same color differently, but only slightly if their brains are normal and all physical factors are not significantly different.

The differences between physically originated variable qualia of the same object among normal people are usually small because the differences in the resulting neural processes and signaling patterns, which are qualia, are only slight. Drastic differences in physically originated variable qualia of the same thing under similar perceiving conditions in healthy people usually do not occur. This is evidenced by the fact that general people do not feel that their perceptions of things are very different from those of others and do not argue about these matters. The differences that occur are readily accepted because they are usually caused by known physical factors, such as short- or long-sightedness, low- or high-frequency hearing loss, and different thicknesses of the palm skin (which affect cutaneous sensations).

However, significant differences can occur in physically originated variable qualia if the perception systems have abnormalities or if the perceiving conditions are different. For example, color blindness can cause visual color qualia to be very different from those in normal people; gustatory (taste) qualia of the same food can be very different among people if the food they consumed immediately before has very different tastes; and various diseases or conditions that affect sensory perception systems can cause qualia that are very different from normal, such as abnormal skin sensation perception (e.g., numbness, hyperesthesia, and paresthesia), abnormal odor perception (e.g., hyposmia, hyperosmia, and parosmia), and abnormal sound perception (e.g., hyperacusis, presbycusis, and diplacusis). Moreover, qualia that are very different from normal can result from illusions, hallucinations, and an interesting syndrome called synesthesia.


Synesthesia is a condition in which a stimulus in one sensory modality, in addition to triggering the primary percept in that modality, automatically and consistently triggers a secondary, concurrent percept in another modality [4–21] or in another type of the same modality. For example, color perceptions occur in addition to sound perceptions when people with music-color synesthesia hear musical sounds or in addition to letter or number visual perceptions when those with grapheme-color synesthesia see letters or numbers. Many scientists believe that synesthesia occurs because there are unusual neural connections between perception neural circuits of different modalities such that, when a perception neural circuit of one modality (such as auditory) is stimulated to function by a stimulus, another perception neural circuit of a different modality (such as visual) will function simultaneously, such as in people with music-color synesthesia. In other types of synesthesia, unusual neural mechanisms activate perception neural circuits of different types but of the same modality, such as the visual perception neural circuit of form and that of color in people with grapheme-color synesthesia [21]. Other possible underlying mechanisms for synesthesia generation include disinhibited feedback, hyperconnectivity, hyperbinding, and enhanced white matter connectivity [19]. However, some studies have shown that synesthetic experiences (e.g., synesthetic perceptions of colors) are not equivalent to real perceptions (e.g., visual perceptions that occur from actually seeing colors) [22] and that the cause of synesthesia may be something else, such as a special kind of childhood memory that is recalled when there is some sensory perception occurring [23] or distributed processing of synesthetic associations [22]. However, despite uncertainty regarding the exact mechanisms that generate synesthesia, it can be concluded that these are physical mechanisms involving neural connections, functions, or both.

Qualia that occur in people with synesthesia thus differ from those in the general population who experience the same thing because there is more than one type of quale co-occurring. Because these extra qualia occur because of physical mechanisms, qualia in these people vary from qualia in general people because of physical causes and are thus physically originated variable qualia.

II.2 Non-Physically Originated Variable Qualia

Non-physically originated variable qualia are qualia that are variable and appear differently among people by themselves, not because of physical causes. They can be classified as listed at the beginning of this chapter. One example of this type of variable qualia is the frequently-talked-about color qualia that can appear red in some people but blue in others (so that “your red is my blue,” as some people suspect). However, theoretically, several other types can manifest themselves variably in other ways, and some of them are interesting and illuminating. Hence, they will be examined in detail as follows:

II.2.1 Randomly variable qualia (RVQ)

Randomly variable qualia (RVQ) are qualia that are randomly variable and appear differently in a random manner among people. They can be subclassified into two groups depending on whether the randomness is complete or partial, as in Table II.1.

II.2.1.1 Randomly variable qualia-complete (RVQc)

Randomly variable qualia-complete (RVQc) are qualia that are randomly variable and appear differently in a completely random manner among people. RVQc of something will appear differently in every instance. For example, if color C qualia are RVQc, they will appear as red, blue, green, and other colors randomly at different points in the reader’s visual field (VF)—they will not appear as the same colors at all the VF points. Moreover, they will do so in the author and other people. (Please see Row 1. RVQc in Table II.1.) Thus, the randomness is complete because the variability occurs in all cases, both in a single individual and in different individuals.

 Manifest in one individual asManifest in several individuals as
RVQcred, blue, green, etc.red, blue, green, etc. in each individual
RVQpa certain colora certain color in one individual but other certain colors in other individuals
Table II.1 Manifestations of a Randomly Variable Color C qualia

II.2.1.2 Randomly variable qualia-partial (RVQp)

Randomly variable qualia-partial (RVQp) are qualia that are randomly variable and appear differently in a partially random manner among people. RVQp of something will appear differently only when they occur in two or more individuals but will not appear differently in any single individual. For example, if color C qualia are RVQp, they will always appear as red in the reader, as blue in the author, as green in another person, as yellow in yet another person, and so on. However, they will not appear as red, blue, green, yellow, etc. (as RVQc do) in any single individual—the reader, the author, or any other person. (Please see Row 2. RVQp, Table II.1). Therefore, in any one individual, they are not variable and will not appear differently; only among two or more individuals will they be variable and appear differently. Thus, they are randomly different in a partial manner because they require two or more individuals to manifest their variability.

The question is whether RVQ occur in the real world. To answer this question, we will investigate them in more detail as follows:

II.2.1.1 Randomly variable qualia-complete (RVQc)

For RVQc, there is evidence that they do not occur in the real world. Consider the following example.

A visual image that occurs in one’s mind is not an all-or-none phenomenon. Instead, the entire visual image comprises millions of independent tiny visual images joined seamlessly by the visual perception neural processes. Each tiny visual image is created by a tiny perception neural process of that point in the visual field. If there is damage to some of these tiny neural processes, it will affect only the tiny images at the corresponding points in the visual field, leaving those in the unaffected part intact. For example, a lesion in the occipital cortex can result in a defect (scotoma) in the corresponding portion of the contralateral visual field, leaving the rest of the visual field undisturbed. In addition, because there are separate perception neural processes for each specific characteristic (i.e., color, shape, and movement) [24,25], various types of defects can occur separately and independently. For example, a unilateral occipitotemporal infarction can result in achromatopsia (cerebral color blindness) in some parts of the contralateral visual field [26–29], while other components (i.e., shape and movement.) of the visual field remain intact. Thus, the entire visual image in the mind comprises millions of independent tiny visual images, each composed of several independent types of visual characteristics.

Now, suppose one is looking at a screen of homogeneous color “C” (Figure II.2A). All the tiny neural processes for color perception must be creating the same signals—the color “C” signal—separately, and the quale for each tiny neural process must be occurring separately. If RVQc are possible, each quale of those millions of tiny neural processes that generate the whole image should manifest itself differently as red, blue, green, or other colors randomly, and the entire visual image should not be a homogeneous color but a mixture of myriad different-color bits (as in Figure II.2B).

Randomly variable qualia

However, in reality, this does not happen. If any quale of the millions of tiny Color “C” neural processes in Figure II.3A manifests itself as red, all the others will also manifest themselves as red, and the screen will be pure red (as in Figure II.3B).

Randomly variable qualia

Similarly, a pair of same-color discs (such as red and red)* is always perceived as a pair of same-color discs (such as red and red, as in Figure II.4A), not a pair of different-color discs (such as red and blue, as in Figure II.4B), which can occur if RVQc are possible because the color in one disc may appear as red, while in the other, as blue.

Randomly variable qualia

(* One may ask, “How do we know that the colors being compared are of the same colors in the first place?”. The answer is that we can know objectively, independently of our perceptions, whether the two or three or more colors that are being compared are of the same color by checking their radiation wavelengths with our instruments—for example, they will be found to have wavelengths of 700 nm if they are red.)

Therefore, for the same colors in the outside world, the same color qualia occur in millions of tiny neural processes, and RVQc do not occur. In addition, it never happens that color qualia occur at only some points in the visual field and that auditory, olfactory, or other kinds of qualia occur at other points in the visual field. This means that qualia do not vary from visual to other types of qualia either.

Similarly, no evidence suggests that the RVQc occur in other sensory perceptions. For example, when two identical musical instruments play the same musical note, “M” (M stands for a certain musical note), the quale of the sound from each instrument will have a chance to manifest itself differently if RVQc are possible; consequently, one may appear as the piano sound of note C, while the other, the violin sound of note G. This is, of course, absurd and never happens; people will hear the two sounds as the same musical note of the same musical instrument, such as the flute sound of note A if the flutes are playing note A. The same scenario is similar for other sensory perceptions, such as the feeling of the same touches on both arms, the pain from the needle stabbing with similar strength on both legs, and the taste of the same honey on both sides of the tongue—the qualia of the same things on both sides are always the same, not randomly different, in any single individual.

Thus, there is no randomness in the manifestation of qualia of the same thing in any single individual. This “no randomness in manifestation in a single individual” of qualia has been consistently true for a long time in billions of humans everywhere nowadays and in the past—no normal person has ever reported having variable qualia occurring when perceiving a homogenous stimulus or identical stimuli. Thus, although RVQc has virtually infinite chances to manifest themselves, they have never done so. Therefore, it can be concluded that RVQc or qualia that are variable and appear differently in a completely random manner do not occur.

It is important to note that the non-occurrence of RVQc is evidence that qualia are physical phenomena governed by some physical laws because, if qualia are non-physical phenomena that are not governed by any physical laws, there would be nothing to control their manifestations: they would be able to appear differently in a completely random manner, and all the strange phenomena in the discussions would occur.

II.2.1.2 Randomly variable qualia-partial (RVQp)

However, is it possible that qualia do not occur differently in a completely random manner in a single individual because all qualia occur in a single person, with one consciousness to experience the qualia, but that they will do so among different individuals, with different consciousness to experience the qualia? If so, then such qualia are not randomly variable in a complete manner but are randomly variable in a partial manner, which is why they are called randomly variable qualia-partial (RVQp). Now, is there evidence that RVQp occur? The answer is that there is evidence that RVQp do not occur either.

Let us consider the case of color qualia in Figure II.5.

Variable qualia - your red is my blue

Figure II.5 Qualia 1 and 2 manifesting as different color pairs in three people

If RVQp occur, then quale 1 can randomly manifest itself in person 1 as red, person 2 as blue, and person 3 as yellow, while quale 2 can do so in person 1 as blue, person 2 as teal, and person 3 as orange-yellow. For quale 1, this is the case of “your red is my blue” for person 2 vs. 1 and “your red is my yellow” for person 3 vs. 1. Now, please re-examine the figure, person 1 will say that qualia 1 and 2 are markedly different in hues and warmth, with quale 1 being much warmer than quale 2. Certainly, persons 2 and 3 will not agree with these remarks. Person 2 will say that the two qualia are not markedly different in their hues and warmth, and quale 1 is not much warmer than quale 2, whereas person 3 will say that the two qualia are only minimally different in hues and warmth.

However, such disagreements do not occur among people with normal vision. When some people with normal vision observe a pair of certain colors to be markedly different in hues and warmth, with the first color being much warmer than the second, such as the pair of red and blue that person 1 sees, other people with normal vision will agree with these observations. This means that they (such as persons 2 and 3) see similar color pairs and not different color pairs, as shown in Figure II.5. Thus, it can be concluded that qualia 1 and 2 do not manifest themselves randomly differently in people so that different color-pairs appear in different people. This provides evidence that RVQp do not occur.

Another piece of evidence is the color wheel. Anyone with normal color vision will agree that the hues of colors in a color wheel, such as the one in Figure II.6A, gradually change from one disc to another.

Randomly variable qualia - color wheels

However, if RVQp occur, the color quale of each disc in the wheel will manifest itself haphazardly. For example, in some people, the pale orange at 12 o’clock in II.6A will be magenta in II.6B; the magenta at 4 o’clock in II.6A, green in II.6B; and the teal at 8 o’clock in II.6A, teal in II.6B. This will result in a color wheel that has the hues of successive discs change not gradually but haphazardly, like the color wheel in Figure II.6B, in some people. But this never happens in billions of people with normal color vision. They always agree that the hues of the colors in a color wheel, like the one in Figure II.6A, gradually change from one successive disc to another. Thus, RVQp do not occur in this case either.

The evidence in auditory perception is that if RVQp occur, the sound qualia of musical notes must be randomly different among people. For example, some may perceive the sound quale of a certain musical note M as the note C, some as the note F, and some as the note A#; and for the next sound that is one semitone higher, or note M#, some people may perceive it as C#, some as Cb, and others as G, because of the randomness of the qualia. If RVQp occur, a musical scale must sound different among people. Similarly, a train of musical notes that have sound qualia as C-D-E-C-E-C-E (i.e., do-re-mi-do-mi-do-mi) in some people may have sound qualia as F-C-B-F-B-F-B (i.e., fa-do-ti-fa-ti-fa-ti) in some people and as something else in others. A train of musical notes will appear as music for some people but as a train of erratic sounds for others. These strange phenomena never happen, however. People agree on the orderly sounds of musical scales and music and the chaotic sounds of noise. Similarly, there are no RVQp occurrences in other sensory perceptions either. For example, all people perceive a series of smoothly increasing vibration or sweetness stimuli as smoothly-increasing-strength stimuli. It is not that some individuals perceive it as haphazardly-changing-strength stimuli, which can occur in some individuals if RVQp are possible.

Therefore, there is no randomness in the manifestation of qualia among individuals. This “no randomness in manifestation” of qualia has been consistently true for a long time in billions of people everywhere nowadays and in the past. Thus, although RVQp have virtually infinite chances of manifesting themselves, they never do so. Hence, it can be concluded that RVQp do not occur in the real world. Moreover, regarding the interesting hypothetical phenomenon of “your red is my blue,” although at first it seems very probable that this phenomenon can occur from variable qualia of this type—RVQp—which is a type that can manifest themselves randomly differently among different people, it has now been shown that that is not the case. RVQp do not occur and is thus not the cause of the “your red is my blue.” Therefore, if this interesting phenomenon occurs, it must arise from the variable qualia of other types, or it might not occur at all. This will be discussed later in the following sections.

II.2.2 Restrictedly variable qualia

Restrictedly variable qualia are qualia that are restrictedly variable and appear differently in restricted ways among people.

Although there is no evidence that qualia manifest differently among people randomly, is it possible that qualia can manifest differently among people in restricted ways? For these restricted types of variable qualia, some rules restrict how they appear differently among people. For example, if the rules are that the reader’s sound-pitch qualia are one semitone higher than the author’s but other characteristics of the sound qualia are the same, then the reader and author will have similar acoustic experiences of all musical notes, chords, music, and so on, and we will never be able to tell that we are experiencing different qualia. Why we cannot distinguish them will be discussed in detail in Section II.2.2.3 Identical-structure qualia. For now, this demonstrates a simple example of restrictedly variable qualia. Theoretically, there are several types of restrictedly variable qualia. Let us study some interesting types to see which can occur among people without people knowing that they are experiencing variable qualia.

II.2.2.1 Inverted qualia

Inverted qualia are qualia that have a certain characteristic inverted [1,3,30–32]. For inverted visual qualia, there are several types. One is the inverted light spectrum qualia that have the spectrum inverted with respect to the wavelength, as shown in Panel B, Figure II.7


Variable qualia - inverted qualia of light spectrum

Figure II.7 Inverted light spectrum qualia with respect to the wavelength

Generally, when people with normal color vision see a spectrum of light, such as that in panel A, they agree that there are distinct changes in color hues around wavelengths of 410, 470, 490, 570, and 610 nm. If the qualia of the light spectrum are inverted with respect to the wavelength for some people, the spectrum will be similar to that in panel B for them. Evidently, people with inverted qualia would not agree with the previous observations. In their spectra (like the one in panel B), distinct changes in color are observed at wavelengths of 510, 550, 630, 650, and 710 nm. However, people with normal color vision do not disagree about the wavelengths at which the light spectrum changes color hues. Therefore, there is no evidence that inverted color qualia of this kind occur in humans.

Another way of inverting the light spectrum qualia is to invert each color into its complementary color (color inversion). This results in an inverted spectrum resembling panel B of Figure II.8.

Variable qualia - inverted qualia by color inversion

Figure II.8 Inverted light spectrum qualia by color inversion

The inverted spectrum of this type has problems similar to those of the previous type—those about hue changes at different wavelengths along the spectrum compared with the original spectrum. Additional examples of incongruity between the two spectra are as follows: i) from wavelengths 580 to 640 nm, the upper spectrum (A) changes from greenish yellow to red, with markedly different hues, but the lower spectrum (B) changes from dark blue to light blue, with slightly different hues; and ii) from wavelengths 510 to 590 nm, the upper spectrum (A) changes from green to yellow, with fairly close hues, but the lower spectrum changes from red-pink to dark blue, with markedly different hues. Therefore, if this type of inverted spectrum occurs among people, they can tell that they are experiencing different color spectra. However, this does not happen. Therefore, there is no evidence that inverted color qualia of this kind occur in humans.

For auditory qualia, a chromatic scale in equal temperament (scale 1), in which C’ is one octave higher than C, and its inverted counterpart (scale 2) below will have the same chords constructed from equivalent notes on each scale and sound different.

Scale 1: C C# D D# E F F# G G# A A# B C’

Scale 2: C’ B A# A G# G F# F E D# D C# C

For example, the chord constructed from the 1st, 5th, and 8th notes (C-E-G) of Scale 1 will sound C Major, which is bright and cheerful; however, the chord constructed from the 1st, 5th, and 8th notes (C’-G#-F) of Scale 2 will sound F Minor, which appears subdued and cheerless. Consequently, the same chord constructed from the inverted scale will sound different and have different aesthetic (e.g., emotional) effects from those constructed from the initial scale. If an inverted scale occurs in some people, they will disagree with people who experienced the initial scale about the mood of a particular chord. However, this never occurs in the real world; the same chords sound similar and have similar aesthetic effects on different people. Therefore, it can be concluded that such inverted auditory qualia do not occur in individuals.

II.2.2.2 Shifted qualia

Shifted qualia are qualia with their spectra shifted up or down along the wavelength or frequency. The situation in the shifted qualia of the light spectrum is similar to that in the inverted qualia. Suppose the spectrum of light is shifted, such as to the reader’s left side as in panel B, Figure II.9. Although we cannot say about the new color qualia that occur in the vacated portion on the right side, we can compare the discernible portion on the left side with its counterpart in panel A, which is part of a normal, non-shifted light spectrum.

Variable qualia - shifted qualia

Figure II.9 Shifted light spectrum qualia along the wavelength

Evidently, people with shifted qualia will not agree with people with non-shifted qualia about at what wavelengths the light definitely changes color hues, such as at wavelengths 410, 470, 490, 570, and 610 nm—similar to the discussion for Figure II.7. Also, they will disagree about changes of color hues in some intervals, such as intervals i and ii—similar to the discussion for Figure II.8. However, these types of disagreements never occur. Thus, like inverted qualia, no evidence of shifted light spectrum qualia occurs among people.

For shifted sound pitch qualia, if the spectrum of sound pitch qualia shifts up or down among people, it will be impossible to prove behaviorally whether a shifted sound pitch occurs, as mentioned before. This is because shifted sound-pitch qualia have the characteristics of the next type of restrictedly variable qualia—identical-structure qualia—which enable them to occur among people without knowing that they are experiencing variable qualia.

II.2.2.3 Identical-structure qualia

Other types of inverted or shifted qualia may occur among people; please see more discussions about this matter in reference 1. However, one type of variable qualia that can theoretically occur in people without people being able to tell that they are experiencing variable qualia is identical-structure qualia. Identical-structure qualia come in sets. Each set occurs in a single individual and comprises qualia with phenomenal manifestations different from their counterparts in other sets. However, all sets have identical qualia structures; that is, they have the same number and types of basic qualia components and the same spectral characteristics (please see more details about the qualia structure in PQ2.5, Chapter 4). One example of identical structure qualia is the shifted sound pitch qualia. Shifted sound-pitch qualia in each set have sound pitches that are shifted higher or lower relative to their counterparts in other sets. However, other sound characteristics are the same: They have the same number and types of basic qualia components: pitch, loudness, timbre, formant, attack, sustain, decay, and release. The spectral characteristics, including all the internal relationships among the qualia in each set, are identical to those in the other sets. For example, the identical regular repetition of the sound of each note in every octave (but in different pitches) and the identical acoustic relations among the notes (such as the major third, perfect fourth, and perfect fifth are consonant intervals; the minor second, major second, and tritone are dissonant intervals) are identical in all sets of shifted sound pitch qualia. Consequently, all sets of shifted sound pitch qualia behave identically, and people cannot distinguish between them.

As another example, consider two-color spectra with identical structural qualia in Figure II.10.

Variable qualia - identical-structure qualia

Figure II.10 Two light spectrum qualia that are identical-structure qualia

The lower panel has qualia that have different phenomenal manifestations from their counterparts in the upper panel and that occur only in some people (so we cannot know what the lower panel’s qualia are like and cannot show them here in the picture). However, the qualia in both panels had the same number and types of basic qualia components: color, brightness, shape, dimension, and movement. The spectral characteristics, including all internal relationships among the qualia in each spectrum of both panels, are the same. For example, how colors change their hues along the spectrum (such as distinct changes in color hues around wavelengths of 410, 470, 490, 570, and 610 nm), the apparent brightness of each wavelength along the spectrum, and the perceived hue difference between colors at different wavelengths (e.g., i. between the colors at 510 and 560 nm, which are indistinct in the upper panel and ii. between the colors at 590 and 640 nm, which are distinct in the upper panel) are the same in both panels. Thus, if such identically structured visual qualia occur among people, they will not be able to tell that they are experiencing different visual qualia.

Regarding the puzzle of whether your red is my blue, if we both experience identical-structure qualia, it will make no difference whether that is the case because, even if your red is my blue, the spectral characteristics of the color qualia in our minds will be identical, rendering the relationships between colors in your spectrum the same as those in my spectrum. This will make every aspect of your experience with the spectrum identical to that of mine. This conclusion can be explained more clearly with an illustration as follows:

Please see Figure II.11. The upper panel is your light spectrum qualia; the lower one is mine, which, at each wavelength, has a color quale different from the corresponding one in your spectrum.

Variable qualia - identical-structure qualia

Figure II.11 Your (upper) and my (lower) light spectrum qualia

Now, even if I see the color quale of the 700 nm light as blue, while you see it as red (i.e., your red is my blue), it will be that, while you see the color quale of the 590 nm light as yellow, which is less warm than your red, I will not see it as yellow, which is warmer than my blue, but will see it as some color that is, similar to your case, less warm than my blue. We will have similar experiences with this pair of color qualia (red vs. yellow in your case and blue vs. some color in mine). What is this “some color”? The answer is that it will probably be a color that does not exist in your spectrum, even though it does in mine. Similarly, while you see the color quale of the 440 nm light as blue, which is much darker and cooler than your red, I will not see it as blue or back to red (which will make your blue my red); I, like you, will see it as some color that looks much darker and cooler than my blue. Again, we will have similar experiences with this pair of colors (red vs. blue in your case and blue vs. some color in mine). What is this “some color”? Once again, the answer is that it will probably be a color that does not exist in your spectrum, even though it does in mine.

Thus, it does not matter whether your red is my blue because, even if it is, my blue will relate to other colors in my spectrum exactly as your red does to others in yours, effectively making my blue appear and behave as if it were red in my spectrum. The same principle applies to all other colors in both spectra. Consequently, both spectra will provide us with identical experiences. This is true for all other identical structure qualia of any type (sound, smell, taste, etc.). Therefore, it does not matter whether identical-structure qualia occur because we will never experience them differently or be able to notice and differentiate them, and they will never have different effects on us. Our worlds will be virtually identical, even if these identical structural qualia occur.

II.3 Summary

From the current evidence, it can be concluded that, in reality,

  • physically originated variable qualia can occur,
  • randomly variable qualia-complete (RVQc) do not occur,
  • randomly variable qualia-partial (RVQp) do not occur, and
  • restrictedly variable qualia in some forms, such as inverted qualia, do not occur, but in some forms, such as identical-structure qualia, may occur, and behaviorally, people will not be able to tell that they are experiencing variable qualia.

However, it is important to note that identical-structure qualia are restrictedly different variable qualia—they cannot occur haphazardly but must occur in some restricted ways, with some rules governing their manifestations. The governing rules are as follows:

  1. They must have different phenomenal manifestations among people.
  2. They must have the same number and types of basic qualia components in all people.
  3. They must have the same spectral characteristics in all people.

In humans, the number and types of basic qualia components of each type of quale are fixed and differ from those of other types. For example, visual qualia always have five basic components: color, brightness, shape, dimension, and movement. In contrast, auditory qualia always have eight basic components: pitch, loudness, timbre, formant, attack, sustain, decay, and release; olfactory qualia always have two basic components: odor type and strength. Moreover, the spectral characteristics of each type of quale are different from those of other types and may be very complex and peculiar, such as the spectral characteristics of the light spectrum, which have color hues and brightness changes idiosyncratically along the spectrum, and the spectral characteristics of the musical scale, which have similar sounds repeated in different pitches every octave regularly. Therefore, if identical-structure qualia do occur, the physical problem about them will be: What is the mechanism that makes the qualia manifest themselves differently among different people yet at the same time manifest themselves restrictedly correctly so that they have not only the same number and types of basic components but also the same unique spectral characteristics of that type of quale among billions of different individuals at different places and different times? And the philosophical question about them will be: Why should qualia manifest themselves differently only in some restricted ways, why not in a totally random way, as RVQc do, or why not not-differently at all?

II.4 Remarks

Theoretically, because the signaling patterns of perception neural processes in different people perceiving the same things under the same conditions are similar and because, according to Theorem IV, those signaling patterns are qualia, qualia (of the same things) in different people are similar. Therefore, according to this theorem, all variable qualia that are not physically originated do not occur. These are the predictions of this theory. Please see their details in Section 10.1.

⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓ ⁓

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