From the Preface: The argument of this book ranges from highly theoretical speculations to highly topical problems of modern art and practical hints for the art teacher, and it is most unlikely that I can find a reader who will feel at home on every level of the argument. But fortunately this does not really matter. The principal ideas of the book can be understood even if the reader follows only one of the many lines of the discussion. The other aspects merely add stereoscopic depth to the argument, but not really new substance. May I, then, ask the reader not to be irritated by the...