Newton’s Colour-Theory and Perception

Abstract

The germ of Newton’s theory of colour, which he first published in 1672 and 1675, is already to be found in one of his earliest notebooks, the Certain Philosophical Questions,¹ which dates from 1664/65. Although I shall not discuss the relevant entries in it in detail, I do want to emphasize one important point: in the manner of thinking which leads Newton to his theory, even at this very early stage, we can distinguish three different kinds of enquiry, which for him are inextricably interwoven: the observation of colours in physical phenomena; considerations of the physiological processes of the optic nerves; and the explanation of the observed phenomena in terms of light-corpuscles and their mechanical behaviour. He makes free use of all three of these lines of enquiry, and sometimes switches suddenly from one to the other.² Although in this notebook none of them seems to be dispensable for his theory, it is perhaps only natural that in the course of drawing up such private notes he does not say anything about their relative importance or their specific roles. In his published papers, however, he becomes more explicit in this respect, particularly when he is intent on denying his reliance on this or that kind of mechanistic explanation.³ As has often been observed, however,⁴ these declarations are sometimes at odds with his actual procedure, not only in developing but also in presenting his theory. Consequently, if we are to deal with the question of the relative importance of the three elements of colour perception, physiological considerations and mechanistic explanations — and doing so is a matter of particular importance in connection with the subsequent criticism of Goethe and Hegel — we have first to take a close look at the role which each of them actually plays within Newton’s theory.