A philosopher as great and at the same time as difficult as Wittgenstein has been the subject of innumerable studies, and universal agreement on how to interpret him cannot be expected. This is true of almost all great thinkers, past and present. That is why we still benefit from studies of Plato, Aristotle, Descartes, Spinoza, Kant, or Hegel, to mention just a few. New studies and scholarly works on Wittgesntein will continue to appear. A] reliable brief orientation to his thought is, if not essential, then at least a very useful way to begin a study of his philosophy. -- From the Preface to the Second Edition