Among the foremost philosophers of the twentieth century, Ludwig Wittgenstein made important contributions to the philosophy of logic, theory of meaning, and philosophical psychology and methodology.

Wittgenstein was born into a wealthy Viennese family and began his education in engineering, before turning his attention to problems of mathematical logic and the philosophy of language. He studied with Bertrand Russell at Cambridge University, where he developed a unique perspective on emerging topics of analytic philosophy. He combined an extraordinary rigor of logical methods with a penetrating, uncompromising demand for clarity and philosophical justification of many aspects of logic and mathematics about which working theorists in the field, including Russell, were willing to take for granted. After World War I, in which he served as an artillery officer in the Austrian army, Wittgenstein's reflections on logic and philosophy took a more ethical and aesthetic turn, due...