The opening of chapter one introduces the reader to Leibniz as he arrives in Paris, ostensibly on a secret mission to establish world peace – or at least to persuade the French king not to attack the German lands – but also (and more importantly to him) to immerse himself in the city’s cultural and intellectual riches. This chapter also presents the immediate historical and political context of the philosophical debate, as well as its ramifications for the deep differences that had been violently tearing Europe apart ever since the wars of religion of the sixteenth century. The subsequent chapters introduce the other players in the debate, Arnauld and Malebranche, and a later chapter is on Spinoza, the radical Jewish atheist whose audacious ideas on God, the human being, and society are lurking in the shadows. (Spinoza insisted that the whole project of theodicy is based on an anthropomorphization of God – God, he insisted, just is Nature, nothing more – and is a project of folly and superstition.) The epilogue indicates why all of this matters, why we should care about what a trio of thinkers from three hundred years ago had to say about the nature of God and of the world.I have tried to write an accessible book on difficult but fascinating perennial philosophical ideas. The debate examined in the book may be an old one – although the setting is the seventeenth century, the roots of the debate lie in antiquity. But the ideas remain relevant for the way in which we think about good and bad, human happiness, the meaning of life, and, among religiously minded people, God. Even readers who are not religious believers should care about how to think about the nature of things, about what it is to be a rational being, and about the status of the values – moral values, political values, even aesthetic values – that inform our thinking.Philosophy need not be confined to professional academics, and there is a real shortage of books that make philosophical discussions of these questions accessible to a general reading public without being either overly technical or “dumbing down” the issues.