To my mind, there is no general fact of philosophy, no large retreat or advance, such that a book of his requires to be included in the explanation of it. The admirable biography A. As a result of broadcasting on the BBC, he became the best-known of British philosophers, and was knighted.
These have to do with the exact nature of sense-data, and the exact nature of material things. First, some philosophical naivete needs to be put aside. It needs to be remembered in this and other connections that Ayer's and Logical Positivism's whole enterprise does not ultimately have to do with language.
It is an admirable retrospect of Ayer's own work, indeed his own introduction to it.
Hallucinations do indeed occur, but we can usefully think of your hallucination, while in a completely dark room, or away from all pages, of seeing before you what you do in fact now see -- as we say, this page of this book.
They are matters that are not at all simple. In Ayer's logical empiricism, philosophy is no longer seen as a metaphysical concern, nor as an attempt to provide speculative truths about the nature of ultimate reality.
He also introduced the directly and indirectly verifiable categories. That is, it is not enough to be independent of other people's ideas, to be inventive and unusual, to be unimitative.
Every verifiable proposition is meaningful, although it may be either true or false. Ayer argues that philosophic propositions are analytic, and that they are concerned with 'relations of ideas.