What is art? —That which is common to all the arts. —But what do they have in common? —This (or especially this): their products invariably lend themselves to value judgements which stem from Aesthetics.

This reply, usually tacit but invariably understood, cannot, however, repress a further question, this time a rhetorical or an ironic one: and what does not lend itself to such judgements? The consensus omnium, acquired during the last two hundred years, can do no more than at best to mark an initial approach to the desired definition.