My title explains itself. But it's misleading. There are more than forty reasons. In fact, there are at least ten to the 82nd power, which, I am told, is the number of atoms in the universe. And that's just in ordinary matter, which makes up only 4.9% of the universe, the rest being dark matter and dark energy. Each of my reasons is an independent point, so I have not organized this book by a succession of chapters or headings. After all, most people only remember a few big ideas or separate points after reading or listening to a book. I've never heard anyone say "Oh, that was a good continuous-process-of-logically-ordered-argumentation" but I've often heard people say, "Oh, that was a good point." Which takes me back to my main point: "Why are you a Catholic?" is a good question. A good question deserves a good answer. Here are forty of mine. Peter Kreeft is a professor of philosophy at Boston College and also at the King's College (Empire State Building), in New York City. He is a regular contributor to several Christian publications, is in wide demand as a speaker at conferences, and is the author of over fifty-five books. Dr. Kreeft is a convert to the Catholic Church from reformed Protestantism. He earned an AB degree from Calvin College, and an MA and PhD from Fordham University, followed by post-doctoral work at Yale University. He has received several honors for achievements in the field of philosophy, including the Woodrow Wilson Award, Yale-Sterling Fellowship, Newman Alumni Scholarship, Danforth Asian Religions Fellowship, and a Weathersfield Homeland Foundation Fellowship.