"Language, Truth and Knowledge" is a collection of essays that emerged from a conference held by the Institute Vienna Circle and the University of Vienna in July 2001. These contributions, published here for the first time, address a variety of topics in the philosophy of Rudolf Carnap. The authors respond to objections against various aspects of Carnap's work, including his program "The Logical Structure of the World" and his views on ontology and realism. The collection demonstrates how the understanding of Carnap's philosophy has evolved in its historical context and illustrates the ongoing relevance of his ideas in contemporary philosophical discussion.