Perhaps the chief “moral proof” argument in defense of the existence of God was termed “universal consent.” It was not regarded as a logical demonstration the point of which was to prove the indubitable existence of Divinity, but it did count for a good deal, writes Alan Charles Kors in his erudite book Atheism in France, 1650-1729: Volume I (1990).

The author cited in defense of this moral proof was Cicero who wrote: “Since a steadfast unanimity continues to prevail among all men without exception, it must be understood that the gods exist.” 

For the French cultural elite in early modern France, however, this moral proof began to bulge and swell and ultimately to crack. The pressure came from two directions. First, it is, after all, the Age of Discovery, and plenty of travelers and missionaries, notes Kors, begin to send back reports to the effect that some tribes they’ve met do not have any idea of Divinity. None whatsoever.

And, second, there are, however few they be, ancient philosophers like Epicurus and Lucretius who were, or who were commonly regarded, as atheists–at least in the sense that they denied divine providence. And, setting aside gnostics who believed in a “remote God” (see Mark Lilla, The Stillborn God), what kind of God is it who is not providential? Surely no Christian God!

It simply won’t do to tighten up the argument so as to claim that “a generality of human beings living in different places and times” have had a notion of Divinity in order to conclude that God exists because, in so doing, one admits of the exceptions to “universal consent.” Nor can you salvage the argument by drawing a distinction between reasonable theists (and, to boot, Christian ones) and unreasonable atheists, with the hope of seeing God as an implication of the reasonableness of many people. The argument, surely, isn’t sound, nor is it valid. The exceptions, in brief, present too many doubts–and doubt is precisely what begins to insinuate itself as we make the long march toward modernity.

In his book A History of Scepticism, Richard Popkin, in fact, shows how Pyrrhonian skepticism in particular resurfaces in early modern Europe. Skepticism, of course, is not atheism (some believers become fideists, for instance), but it does open the door through which a strange new animal–modern atheism–will soon appear…