Page:Nature and Life (1934).pdf/74

perceive Nature through our senses. Also, in the analysis of sense-perception we are apt to concentrate upon its most clear-cut instance, namely, sight. Now visual perception is the final product of evolution. It belongs to high-grade animals — to vertebrates and to the more advanced type of insects. There are numberless living things which afford no evidence of possessing sight. Yet they show every sign of taking account of their environment in the way proper to living things. Also, human beings shut off sight with peculiar case, by closing their eyes or by the calamity of blindness. The information provided by mere sight is peculiarly barren — namely, external regions disclosed as coloured. There is no necessary transition of colours, and no necessary selection of regions, and no necessary mutual adaptation of the display of colours. Sight at any instant merely provides the passive fact of regions variously coloured. If we