Ludwig Wittgenstein (1889-1951) was one of the most influential philosophers of the twentieth century. He was born in Vienna, but studied and practiced philosophy in Great Britain. He was a professor of philosophy at the University of Cambridge from 1939 until 1947. He worked in--and transformed--the fields of logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. Victor Rodych is professor of philosophy at the University of Lethbridge. He is coauthor of Introduction to Logic, 15th Edition. Yvonne Lampert is head of philosophy at the Ministry of Schools and Vocational Education in Hamburg. Harry Tomany holds a PhD in philosophy from the University of Reading.