Bad Philosophy: Clark’s Argument against Spectrum Inversion

Many philosophical debates are haunted by Locke’s thought experiment of spectrum inversion: “if the idea that a violet produced in one man’s mind by his eyes were the same that a marigold produced in another man’s, and vice versa” [1].

Austen Clark attempted to prove rigorously that spectrum inversion would be detectable by observing the subjects’ response to colours [2, 3]. He argued as follows: Suppose that two people perceive mutually inverted spectra and agree in their judgements of visual stimuli and the relations between them. Therefore, the colour solid (i.e. the visible colours as co-ordinates in some space) must exhibit symmetry. Since this solid (represented in three-dimensional Euclidean space e.g. as the Munsell colour system [4]) is in fact asymmetric, the premise must be false.

Can you spot the fallacy? It stems from assuming that everyone’s colour solid is identical. Clark mistook a textbook model for the real thing — a fallacy known as reification. Both the Munsell colour system and other proposed colour solids abstract away from differences in visual perception that occur among observers and even across experiments with the same observer [5–9]. One can easily conceive of a personal colour solid that remains the same (within measurement error) when mirrored or rotated. If there cannot be people who function like us with a mirrored or rotated colour solid, it is not its asymmetry that forbids their existence.

[1] Locke, John. “An Essay Concerning Human Understanding”, book II, ch. XXXII, par. 15.

[2] Clark, Austen. Spectrum Inversion and the Color Solid. Southern Journal of Philosophy, vol. 23, no. 4, Winter 1986, pp. 431–443.

[3] Clark, Austen. “A Theory of Sentience”. Oxford University Press: 2000. pp. 17–18.


[5] Webster, Michael A.; Eriko Miyahara; Gokhan Malkoc; Vincent E. Raker. Variations in normal color vision. I. Cone-opponent axes. Journal of the Optical Society of America, vol. 17, no. 9, September 2000, pp. 1535–1544.

[6] Webster, Michael A.; Eriko Miyahara; Gokhan Malkoc; Vincent E. Raker. Variations in normal color vision. II. Unique hues. Journal of the Optical Society of America, vol. 17, no. 9, September 2000, pp. 1545–1555.

[7] Webster, Michael A.; Shernaaz M. Webster; Shrikant Bharadwaj; Richa Verma; Jaikishan Jaikumar; Gitanjali Madan; E. Vaithilingham. Variations in normal color vision. III. Unique hues in Indian and United States observers. Journal of the Optical Society of America, vol. 19, no. 10, October 2002, pp. 1951–1962.

[8] Malkoc, Gokhan; Paul Kay; Michael A. Webster. Variations in normal color vision. IV. Binary hues and hue scaling. Journal of the Optical Society of America, vol. 22, no. 10, October 2005, pp. 2154–2168.

[9] Juricevic, Igor; Michael A. Webster. Variations in normal color vision. V. Simulations of adaptation to natural color environments. Visual Neuroscience, vol. 26, no. 1, January 2009, pp. 133–145.

Bad Philosophy: Clark’s Argument against Spectrum Inversion

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Do Tybru

Wspaniała rzeko, której fala spaja
siedem wzgórz, chlubo Auzonii wiekowa,
dziś twą wspominam z bólem, co się zdwaja,
spokojną przystań, gdzie głąb oliwkowa.

Nie znam powietrza, co tak uspokaja,
skał, rzek, łąk, jaru, co by tak czarował
jak męka krzyża, co serce przepaja,
gdy ją powtarzam w słodkich włoskich słowach.

Bardziej łagodnych pieśni w chmurnej Dacji
brzmiących z fujarek nie słyszałem młodo
od śpiewnej liry Petrarki tonacji.

Nigdziem nie widział z wdzięczniejszą pogodą
dwóch gwiazd cudniejszych wśród piękniejszych gracji
niż dziś świecące łacińskim narodom.

Coat of arms of Romania
Coat of arms of Romania. Source: Wikipedia

Above is the Polish translation of the first Romanian sonnet, written in 1810 by Gheorghe Asachi. I translated and published it to celebrate the 1st of December, the National Day of Romania. Here is the original poem:

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O, tu, râule mărețe, ce întinzi a tale unde
Între șepte colnici, faima al Ausoniei vechite,
De la tine rechem astăzi, în durerile profunde,
Adăpost și lin repaos lângă râpele-nverzite.

Mai plăcut și senin aer nu-l aflai încă oriunde,
Văi, preluci, stânci, râurele ce atât să mă învite
Ca cea patimă-ncruzită care inima-mi pătrunde
S-o rezic în dulcea limbă al Italiei mărite.

Nici sunând pe fluier doine încă-n Dacia umbroasă
N-auzit-am în junie dulce viersuri așa line
Precum sun-a lui Petrarca lira cea armonioasă.

Nici aiure mai duioase nu văzui, nici mai senine
Două stele-ncântătoare între grații mai frumoase
Decât care lucesc astăzi preste țările latine.

If you speak Romanian and would like to judge my version, here is its literal re-translation into English and some notes:

[O] glorious river whose wave bonds
seven hills, [o] ages-old pride of Ausonia,
today I recall with pain that doubles itself your
quiet haven where olive-green depth [is].

I do not know air that calms down [someone, not itself] so much,
rocks, rivers, meadows, ravine that would enchant so much
as the torment of the cross that imbues the heart
when I repeat it in sweet Italian words.

More gentle songs in cloudy Dacia
sounding from pipes I did not hear young
than the melodious tone of Petrarch’s lyra.

Nowhere did I see with more charming serenity
two more marvellous stars among more beautiful graces
than [the ones] today lighting for the Latin nations.

 2. Ausonia = Italy. I have “pride of Ausonia” in vocative (=Tiber). I am unable to make it accusative (=Rome).
 6. “Enchant” is singular, it attaches to the ravine only.
 8. Fun fact: our word for Italian comes from the word for Vlach.
 9. Nobody would know what a doina is.
11. Artistic licence: tone = musical key, like C major. This line can also be read “than the tone of Petrarch’s melodious lyra” with no harm to the meaning.
14. I have no idea what these (two?) stars mean. Also, nations ≠ countries, sigh.

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