This History of Philosophy is intended as an introduction to philosophy itself. The approaches to philosophy are many, but if one aims to give the reader, beyond mere factual information, a genuine philosophical formation, the historical approach becomes a necessity. Much more important than knowledge about philosophy is a true notion of what it is to philosophize. And what better way is there to learn to philosophize than to observe the great philosophers of the past? If one has the understanding and the patience to follow the discussions of Plato, Aristotle, Thomas Aquinas, or Kant, he cannot fail to appreciate what it means to philosophize. And, equally important, he will have a standard of philosophical excellence that will deter him from confusing a shabby piece of philosophy with one that is first-rate.