Available for the first time in 20 years, here are two important works from the 1920s by the best-known representative of the Vienna Circle. In The Logical Structure of the World, Carnap adopts the position of "methodological solipsism" and shows that it is possible to describe the world from the immediate data of experience. In his Pseudoproblems in Philosophy, he asserts that many philosophical problems are meaningless.

Available for the first time in 20 years, here is the Rudolf Carnap's famous "principle of tolerance" by which everyone is free to mix and match the rules of language and logic. In The Logical Syntax of Language, Carnap explains how his entire theory of language structure came to him like a vision when he was ill. He postulates that concepts of the theory of logic are purely syntactical and therefore can be formulated in logical syntax.