The following passage from Ruskin's Ethics of the Dust (Lecture X) brings out his criticism of the scientific way of treating of optical phenomena:

Just as the simple light-dark after-image shows a reversal of light-values in relation to the external picture, so in the coloured afterimages there is a quite definite and opposite relationship of their colours to those of the original picture. Thus, if the eyes are exposed for some time to an impression of the colour red, and then directed to a neutral surface, not too brightly illuminated, one sees it covered with a glimmering green. In this way there is a reciprocal correspondence between the colour-pairs Red-Green, Yellow-Violet, Blue-Orange. To whichever of these six colours one exposes the eye, an after-image always appears of its contrast colour, forming with it a pair of opposites.

'With regard to the most interesting of all their [the philosophers'] modes of force-light; they never consider how far the existence of it depends on the putting of certain vitreous and nervous substances into the formal arrangement which we call an eye. The German philosophers began the attack, long ago, on the other side, by telling us there was no such thing as light at all, unless we choose to see it.² Now, German and English, both, have reversed their engines, and insist that light would be exactly the same light that it is, though nobody could ever see it. The fact being that the force must be there, and the eye there, and 'light' means the effect of the one on the other - and perhaps, also - (Plato saw farther into that mystery than anyone has since, that I know of) - on something a little way within the eyes.'

We must here briefly recall how this phenomenon is generally explained on Newtonian lines. The starting-point is the assumption that the eye becomes fatigued by gazing at the colour and gradually becomes insensitive to it. According to Newton's theory, if an eye thus affected looks at a white surface, the sum of all the colours comes from there to meet it, while the eye has a reduced sensitivity to the particular colour it has been gazing at. And so among the totality of colours constituting the 'white' light, this one is more or less non-existent for the eye. The remaining colours are then believed to cause the contrasting colour-impression.

Remarks like these, and the further quotation given below, make it seem particularly tragic that Ruskin apparently had no knowledge of Goethe's Farbenlehre. This is the more remarkable in view of the significance which Turner, with whom Ruskin stood in such close connexion, ascribed to it from the standpoint of the artist. For the way in which Ruskin in his Modern Painters speaks of the effect of the modern scientific concept of colours upon the ethical-religious feeling of man, shows that he deplores the lack of just what Goethe had long since achieved in his Farbenlehre where, starting with purely physical observations, he had been able to develop from them a 'physical-moral' theory of colour.

If we apply the common sense of the Hans Andersen child to this, we see where it actually leads. For it says no less than this: as long as the eye is in a normal condition, it tells us a lie about the world, for it makes white light seem something that in reality it is not. For the truth to become apparent, the natural function of the eye must be reduced by fatigue. To believe that a body, functioning in this way, is the creation of God, and at the same time to look on this God as a Being of absolute moral perfection, would seem a complete contradiction to the Hans Andersen child. In this contradiction and others of the same kind to which nowadays every child is exposed repeatedly and willy-nilly in school lessons and so on - we must seek the true cause of the moral uncertainty so characteristic of young people today. It was because Ruskin felt this that he called for a 'moral' theory of light.

Having made ourselves so far acquainted with the fundamentals of Goethe's approach to the outer phenomena of colour involved in the spectrum, we will leave this for a while to follow Goethe along another no less essential line of inquiry. It leads us to the study of our own process of sight, by means of which we grow aware of the optical facts in outer space.

Ruskin's alertness to the effect on ethical life of a scientific world-picture empty of all qualitative values led him to write:

Since Goethe did not judge man from artificially devised experiments, but the latter from man, quite simple reflexions led him to the following view of the presence of the contrasting colour in the coloured after-images. Nature outside man had taught him that life on all levels takes it course in a perpetual interplay of opposites, manifested externally in an interplay of diastole and systole comparable to the process of breathing. He, therefore, traced the interchange of light-values in colourless after-images to a 'silent resistance which every vital principle is forced to exhibit when some definite condition is presented to it. Thus, inhalation presupposes exhalation; thus every systole, its diastole. When darkness is presented to the eye, the eye demands brightness, and vice versa: it reveals its vital energy, its fitness to grasp the object, precisely by bringing forth out of itself something contrary to the object.'