Who was Wittgenstein? It is no easy matter to answer this question, for Wittgenstein is still so close to us, still so much a figure of our own time, still so much talked about, exalted and denounced, that an objective and balanced appraisal is difficult to achieve. Posterity must determine his exact place in the history of philosophy; but at any rate there can be no doubt that he was a genius. This is not to say that he was the only genius, or even the greatest genius, in twentieth-century philosophy: indeed it scarcely matters whether he was or was not: what does matter is that Wittgenstein's work in philosophy was passionate, intense, inspired. He dedicated himself to it; philosophy was his life. Every train of thought that he might have followed with greater zeal, every problem that he might have worked on with a fiercer determination, was not, for him, something that he might have done better; it was a betrayal of his real mission in life, treason against his own existence, a sin. Such total commitment to philosophy allows us to compare Wittgenstein with the greatest names in the history of the subject: what was characteristic of Socrates and Spinoza was characteristic also of him.