The sense of beauty has a more important place in life than aesthetic theory has ever taken in philosophy. The plastic arts, with poetry and music, are the most conspicuous monuments of this human interest, because they appeal only to contemplation, and yet have attracted to their service, in all civilised ages, an amount of effort, genius, and honour, little inferior to that given to industry, war, or religion. The fine arts, however, where æsthetic feeling appears almost pure, are by no means the only sphere in which men show their susceptibility to beauty. In all products of human industry we notice the keenness with which the eye is attracted to the mere appearance of things: great sacrifices of time and labour are made to it in the most vulgar manufactures; nor does man select his dwelling, his clothes, or his companions without reference to their effect on his æsthetic senses. Of late we have even learned that the forms of many animals are due to the survival by sexual selection of the colours and forms most attractive to the eye. There must therefore be in our nature a very radical and wide-spread tendency to observe beauty, and to value it. No account of the principles of the mind can be at all adequate that passes over so conspicuous a faculty.