Leo Stein (1872–1947) was an influential art collector and critic. It has been Stein’s ironic fate to be referred to as “Gertrude’s brother,” ironic as for many years he was her mentor and counsellor.

"The A-B-C of Aesthetics" considers the field of aesthetics not from a theoretical and discursive angle, not as a matter of classification and conceptual method, but from a basis of practical experience. The author insists that the importance of the aesthetic experience is something “as essentially practical as food.”

Stein argues in this book that an understanding of the meaning and implication of the aesthetic experience can only come through doing, not through argument and intellectualization.

Aesthetic perception is a special way of grasping the realities in us and about us. It is not limited to the narrow outlook of specialists, artists, or their critics.