This psychological reaction of children to colour is not surprising if one knows the role played by the blood in the process of seeing, and how differently the soul-life of man is connected with the blood-nerve polarity of his organism in childhood and in later life. What we have described as the polar interplay of blood and nerve in the act of sight is not confined to the narrow field of the eye. Just as the nerve processes arising in the retina are continued to the optic centre in the cerebrum, so must we look for the origin of the corresponding blood process not in the choroid itself, but in the lower regions of the organism. Wherever, therefore, the colour red influences the whole nerve system, the blood system as a whole answers with an activity of the metabolism corresponding to the contrasting colour, green. Similarly it reacts as a whole to a blue-violet affecting the nerve system, this time with a production corresponding to yellow-orange. The reason why in later years we notice this so little lies in a fact we have repeatedly encountered. The consciousness of the grown man to-day, through its one-sided attachment to the death-processes in the nerve region, pays no attention to its connexion with the life-processes centred in the blood system. In this respect the condition of the little child is quite different. Just as the child is more asleep in its nerve system than the grown-up person, it is more awake in its blood system. Hence in all sense-perceptions a child is not so much aware of how the world works on its nerve system as how its blood system responds. And so a child in a red environment feels quietened because it experiences, though dimly, how its whole blood system is stimulated to the green production; bluish colours enliven it because it feels its blood answer with a production of light yellowish tones. From the latter phenomena we see once more the significance of Goethe's arrangement of his Farbenlehre. For we are now able to realize that to turn one's attention to the deeds and sufferings of the inner light means nothing less than to bring to consciousness the processes of vision which in childhood, though in a dreamlike way, determine the soul's experience of seeing. Through placing his examination of the physiological colours at the beginning of his Farbenlehre, Goethe actually took the path in scientific research to which Thomas Reid pointed in philosophy. By adapting Reid's words we can say that Goethe, in his Farbenlehre, proclaims as a basic principle of a true Optics: that we must become again as little children if we would reach a philosophy of light and colours. 1Wär' nicht das Auge sonnenhaft, Wie könnten wir das Licht erblicken? Lebt' nicht in uns des Gottes eigne Kraft, Wie könnt' uns Göttliches entzucken! 2 Inquiry, VI, 1. The italics are Reid's. 3 Presumably Kant and his school. Schopenhauer was definitely of this opinion.