On Sense And The Sensible   

(1) It is conceivable that the White and the Black should be

juxtaposed in quantities so minute that [a particle of] either

separately would be invisible, though the joint product [of two

particles, a black and a white] would be visible; and that they should

thus have the other colours for resultants. Their product could, at

all events, appear neither white nor black; and, as it must have

some colour, and can have neither of these, this colour must be of a

mixed

character- in fact, a species of colour different from either. Such,

then, is a possible way of conceiving the existence of a plurality

of colours besides the White and Black; and we may suppose that [of

this 'plurality'] many are the result of a [numerical] ratio; for

the blacks and whites may be juxtaposed in the ratio of 3 to 2 or of 3

to 4, or in ratios expressible by other numbers; while some may be

juxtaposed according to no numerically expressible ratio, but

according to some relation of excess or defect in which the blacks and

whites involved would be incommensurable quantities; and, accordingly,

we may regard all these colours [viz. all those based on numerical

ratios] as analogous to the sounds that enter into music, and

suppose that those involving simple numerical ratios, like the

concords in music, may be those generally regarded as most

agreeable; as, for example, purple, crimson, and some few such

colours, their fewness being due to the same causes which render the

concords few. The other compound colours may be those which are not

based on numbers. Or it may be that, while all colours whatever

[except black and white] are based on numbers, some are regular in

this respect, others irregular; and that the latter [though now

supposed to be all based on numbers], whenever they are not pure,

owe this character to a corresponding impurity in [the arrangement of]

their numerical ratios. This then is one conceivable hypothesis to

explain the genesis of intermediate colours.

(2) Another is that the Black and White appear the one through the