Is man incomprehensible to man?

There is no agreement today on the meaning of phrases like 'Human Nature' or 'The Nature of Man,' or even on whether they mean anything at all. Here is a thoughtful, contemporary survey of philosophy from Aristotle to McLuhan and Marcuse that never loses its focus on the issue: who is man? Central to the discussion is the view of Man as Inventor, the inventor of symbols as well as tools. This is a unifying vision, for "The highest powers of abstract thought depend on man's ability to construct and manipulate symbols."