THIS little book, like the great branch of mental science to which it is an introduction, makes no attempt to "form the taste" of the public and still less to direct the doings of the artist. It deals not with _ought_ but with _is,_ leaving to Criticism the inference from the latter to the former. It does not pretend to tell how things can be made beautiful or even how we can recognise that things _are_ beautiful. It takes Beauty as already existing and enjoyed, and seeks to analyse and account for Beauty's existence and enjoyment. More strictly speaking, it analyses and accounts for Beauty not inasmuch as existing in certain objects and processes, but rather as calling forth (and being called forth by) a particular group of mental activities and habits. It does not ask: What are the peculiarities of the things (and the proceedings) which we call _Beautiful?_ but: What are the peculiarities of our thinking and feeling when in the presence of a thing to which we apply this adjective? The study of single beautiful things, and even more, the comparison of various categories thereof, is indeed one-half of all scientific aesthetics, but only inasmuch as it adds to our knowledge of the particular mental activities which such "Beautiful" (and vice versa "Ugly") things elicit in us. For it is on the nature of this active response on our own part that depends the application of those terms _Beautiful_ and _Ugly_ in every single instance; and indeed their application in any instances whatsoever, their very existence in the human vocabulary.