THE TRACTATUS LOGICO-PHILOSOPHICUS is the only book-length philosophical work published by the Austrian philosopher Ludwig Wittgenstein in his lifetime. The project had a broad aim - to identify the relationship between language and reality and to define the limits of science - and is recognized as a significant philosophical work of the twentieth century. Wittgenstein wrote the notes for the Tractatus while he was a soldier during World War I and completed it when a prisoner of war at Como and later Cassino in August 1918