A significant number of atheists claim that belief in the existence of God is irrational and incapable of proof. It is the purpose of the following work to respond to and dispel this error and to offer detailed proofs, drawn solely from human reason, which demonstrate God's existence with absolute certainty. Having demonstrated the existence of God, we will proceed to show that men have immaterial souls, not reducible to the brain or to any material object, which are capable of performing immaterial actions like understanding and willing, and that these souls can and indeed must continue to exist even after bodily death. From there we will show the possibility of divine revelation, which is to say that God can reveal Himself to human beings. The marks of this revelation, as the First Vatican Council teaches, are particularly to be found in miracles, which are actions that only God can perform, and true prophecies, which consist in knowledge that only God can possess. Actual miracles have occurred in history, even down to our times, undeniable examples of which will be provided. Supposing, though, that a reader who takes up this study as an atheist recognizes the truth of the proofs and concludes that God exists and can reveal Himself, the question which would naturally arise in his mind is whether God actually has revealed anything about Himself to men and, if so, what He has revealed. A merely cursory knowledge of global demographics reveals that of the approximately 7 billion people comprising the world’s population, over a billion profess Catholicism, more than a billion more follow Islam, another billion or more, Protestantism or some other Christian sect, and many others, Judaism, Buddhism, Hinduism, Mormonism, or some form of pagan religion. From these statistics the reader concludes that although vast numbers of the world's population agree as to some or many of the truths noted, such as the existence of God, no such agreement exists as to what God has revealed about Himself, but instead we find the widest divergence. An agnostic or even an undecided theist, faced with this apparent chaos, might be tempted to throw up his hands in despair of finding the true path. Thus the second part of this book will be devoted to proving that of all the claimed revelations made by God, only one—Christianity—is true. This will include an examination of the historical truth of the Gospels, together with proofs of the Resurrection and divinity of Jesus Christ. Given the large number of religions claiming to represent true Christianity, however, the third part of the book will show that of all the varying forms of Christianity, there, too, only one—Catholicism—is and can be true. This section will discuss the proof that Christ established a church and the signs by which one can recognize it, Catholicism's teachings, Sacraments, and Creed, the Church's contributions to science and civilization, a defense of the Church's more unpopular moral teachings on abortion, birth control, and homosexual activity, and replies to many other objections. This book aims to take the reader via a step-by-step proof from atheism to theism, from theism to Christianity, and from Christianity to Catholicism, using reason, logic, and argument rather than appeals to emotion.