There was a time when ethics could take the simple form of comparing what man does with what he ought to do, known as the good. The ‘good’ invariably turned out to be whatever the author of the book was accustomed to and found sanctioned by his community. Ethical writers now, though they still have values, tend to look at their problems rather differently. But a procedure which is hopelessly outmoded in ethics is still in vogue among writers on aesthetic problems. It is still possible for a critic to define as authentic art whatever he happens to like, and to go on to assert that what he happens not to like is, in terms of that definition, not authentic art. The argument has the great advantage of being irrefutable, as all circular arguments are, but it is shadow and not substance.

Northrop Frye, Anatomy of Criticism: Four Essays (1957)