In so far as aesthetics is studied by the objective method it is a branch of psychology. Aesthetic facts are mental facts. A work of art, no matter how material it may at first seem to be, exists only as perceived and enjoyed. The marble statue is beautiful only when it enters into and becomes alive in the experience of the beholder. Keys and strings and vibrations of the air are but stimuli for the auditory experience which is the real nocturne or etude. Ether vibrations and the retina upon which they impinge are nothing more than instruments for the production of the colors which, together with the interpretation of them in terms of ideas and feelings, constitute the real picture which we appreciate and judge. The physical stimuli and the physiological reactions evoked by them are important for our purpose only so far as they help us to understand the inner experiences with which they are correlated. A large part of our work, therefore, will consist in the psychological analysis of the experience of art and the motives underlying its production. We shall have to distinguish the elements of mind that enter into it, show their interrelations, and differentiate the total experience from other types of experience. Since, moreover, art is a social phenomenon, we shall have to draw upon our knowledge of social psychology to illumine our analysis of the individual's experience. Art is a historical, even a technical, development; hence the personal enjoyment of beauty itself is conditioned by factors that spring from the traditions of groups of artists and art lovers. No one can understand his pleasure in beauty apart from the pleasure of others.