In view of the present scientific conception of the effect which a prismatic piece of a transparent medium has on light passing through it, Goethe's objection to Newton's interpretation and the conclusions drawn from it seems by no means as heretical as it did in Goethe's own time and for a hundred years afterwards. For, as Lord Rayleigh and others have shown, the facts responsible for the coming into being of the spectral colours, when these are produced by a diffraction grating, invalidate Newton's idea that the optical apparatus serves to reveal colours which are inherent in the original light. Today it is known that these colours are an outcome of the interference of the apparatus (whether prism or grating) with the light. Thus we find Professor R. W. Wood, in the opening chapter of his Physical Optics, after having described the historical significance of Newton's conception of the relation between light and colour, saying: 'Curiously enough, this discovery, which we are taking as marking the beginning of a definite knowledge about light, is one which we shall demolish in the last chapter of this book,2 for our present ideas regarding the action of the prism more nearly resemble the idea held previous to Newton's classical experiments. We now believe that the prism actually manufactures the coloured light.' We find ourselves faced here with an instance of the problem, 'Discovery or Manufacture?' dealt with by Eddington in the manner described in our previous chapter. This very instance is indeed used by Eddington himself as a case in which the answer is definitely in favour of 'manufacture'. Nevertheless, Eddington complains, experts, in spite of knowing better, keep to the traditional way of speaking about the spectral colours as being originally contained in the light. 'Such is the glamour of a historical experiment.'3 It is for the same reason that Goethe's discovery continues to be unrecognized by the majority of scientists, who prefer, instead of examining the question for themselves, to join in the traditional assertion that 'Goethe never understood Newton'. * As Goethe relates at the conclusion of the 'historical' part of his Farbenlehre,4 he was drawn to study colour by his wish to gain some knowledge of the objective laws of aesthetics. He felt too close to poetry to be able to study it with sufficient detachment, so he turned to painting - an art with which he felt sufficiently familiar without being connected with it creatively - hoping that if he could discover the laws of one art they would prove applicable to others. His visit to Italy, a land rich both in natural colour and in works of art, gave him a welcome opportunity to pursue this inquiry, but for a long time he made no headway. The paintings he saw suggested no inherent law in their arrangement of colours, nor could the painters he questioned tell him of one. The only qualitative distinction they seemed to recognize was between 'cold' and 'warm' colours.