Voltaire kept reading Pascal's "Pensees" throughout his life. He thoroughly perused them and made detailed notes in three stages from about 1728 until 1777. He let Pascal have his say. He prints detailed quotations and counters them with his criticism. Voltaire conducts a serious philosophical discussion with the author of the "Pensees" whom he recognizes as a genius. He calls it a battle of the giants. This has resulted in a document of great importance. It illuminates the intellectual, religious, and political landscape of the time like a flash of lightning: Voltaire considered Pascal's Christianity as archaic, implausible, hostile towards life. There is no clearer or more polished text on the relationship between Enlightenment and Christianity. At the same time, it is also a stylistic delight; two of the most original and witty writers in France are engaged here. Flasch's book presents the texts in translation and determines their historical and factual significance. It describes for the first time from the sources the emergence of the problem situation from the late Augustine to Jansenius, Pascal and Voltaire.