The importance which Goethe himself saw in this aspect of the optical problem is shown by the place he gave it in the didactic part of his Farbenlehre. The first three chapters, after the Introduction, are called 'Physiological Colours', 'Physical Colours', and 'Chemical Colours'. In the first chapter, Goethe summarizes a group of phenomena which science calls 'subjective' colours, since their origin is traced to events within the organ of sight. The next chapter deals with an actual physics of colour - that is, with the appearance of colours in external space as a result of the refraction, diffraction and polarization of light. The third chapter treats of material colours in relation to chemical and other influences. After two chapters which need not concern us here comes the sixth and last chapter, entitled 'Physical-Moral Effect of Colour' ('Sinnlich-sittliche Wirkung der Farben'), which crowns the whole. There, for the first time in the history of modern science, a bridge is built between Physics, Aesthetics and Ethics. We remember it was with this aim in view that Goethe had embarked upon his search for the solution of the problem of colour.

'It is in raising us from the first state of inactive reverie to the second of useful thought, that scientific pursuits are to be chiefly praised. But in restraining us at this second stage, and checking the impulses towards higher contemplation, they are to be feared or blamed. They may in certain minds be consistent with such contemplation, but only by an effort; in their nature they are always adverse to it, having a tendency to chill and subdue the feelings, and to resolve all things into atoms and numbers. For most men, an ignorant enjoyment is better than an informed one, it is better to conceive the sky as a blue dome than a dark cavity, and the cloud as a golden throne than a sleety mist. I much question whether anyone who knows optics, however religious he may be, can feel in equal degree the pleasure and reverence an unlettered peasant may feel at the sight of a rainbow.'

Consequently he summarizes his reflexions on coloured afterimages and their reversals of colour in these words: 'The eye demands actual completeness and closes the colour-circle in itself.' How true this is, the law connecting the corresponding colours shows, as may be seen in the following diagram. Here, red, yellow and blue as three primary colours confront the three remaining colours, green, violet and orange in such a way that each of the latter represents a mixture of the two other primary colours. (Fig. 10.)

In this chapter the experiencing of the various colours and their interplay through the human soul is treated in many aspects, and Goethe is able to show that what arises in man's consciousness as qualitative colour-experience is nothing but a direct 'becoming-inward' of what is manifested to the 'reader's' eye and mind as the objective nature of colours. So, in one realm of the sense-world, Goethe succeeded in closing the abyss which divides existence and consciousness, so long as the latter is restricted to a mere onlooker-relationship towards the sense-world.

What Ruskin did not guess was that the rudiments of the 'moral theory of light' for which he craved, as this passage indicates, had been established by Goethe long before.

Colour and contrast-colour are actually so related that to whatever colour the eye is exposed it produces a counter-colour so as to have the sum-total of all the three primary colours in itself. And so, in consequence of the interplay of outer and inner light in the eye, there is always present in it the totality of all the colours.

If we ask what induced Goethe to treat the physiological colours before the physical colours, thus deviating so radically from the order customary in science, we shall find the answer in a passage from the Introduction to his Entwurf. Goethe, in giving his views on the connexion between light and the eye, says: 'The eye owes its existence to light. Out of indifferent auxiliary animal organs the light calls forth an organ for itself, similar to its own nature; thus the eye is formed by the light, for the light, so that the inner light can meet the outer.' In a verse, which reproduces in poetic form a thought originally expressed by Plotinus, Goethe sums up his idea of the creative connexion between eye and light as follows:

In the section of his Farbenlehre dealing with 'physiological colours', Goethe devotes by far the most space to the so-called 'afterimages' which appear in the eye as the result of stimulation by external light, and persist for some little time. To create such an afterimage in a simple way, one need only gaze at a brightly lit window and then at a faintly lit wall of the room. The picture of the window appears there, but with the light-values reversed: the dark cross-bar appears as light, and the bright panes as dark.

It follows that the appearance of the contrast-colour in the field of vision is not, as the Newtonian theory asserts, the result of fatigue, but of an intensified activity of the eye, which continues even after the colour impression which gave rise to it has ceased. What is seen on the neutral surface (it will be shown later why we studiously avoid speaking of 'white light') is no outwardly existing colour at all. It is the activity of the eye itself, working in a dreamlike way from its blood-vessel system, and coming to our consciousness by this means.

' Unless our eyes had something of the sun, How could we ever look upon the light? Unless there lived within us God's own might, How could the Godlike give us ecstasy?¹