Joseph Ratinzger was, in addition to a profound pontiff and rigorous theologian, one of the most consistent and important thinkers of the last century. This book aims, in addition to discovering the main milestones of his career, to explain to a wide audience his main contributions. Starting from the philosophical analysis of his work, the aim of these pages is to give an account of Benedict XVI's efforts to broaden the horizons of reason, as well as his interest in curing the excesses of rationalism, appealing to faith, and those of fideism, critically integrating reason into the theological sphere. A book, then, that serves as an introduction to the contributions of Benedict XVI, the Pope of reason. From the famous debate between Ratzinger and the philosopher Habermas in January 2004 at the Catholic Academy of Bavaria, the following conclusions are drawn: Religion and secular reason should take each other seriously in a never-ending process of complementary learning. Jürgen Habermas The Church Fathers have been teaching for many years that reason and faith are complementary.