We are actually always passing each other’s sanity assessments but failing God’s, he wrote. I’m always passing your assessment and you’re always passing mine, always with flying colors, this is what a conversation is, an alternating series of not-very-stringent sanity assessments, though in God’s eyes presumably we’re frequently mad.

Still we never increase the stringency of our assessments!

Of course, even the most stringent human assessment is ridiculous in light of even the laxest assessment administered by God, Leibniz wrote.

It is worth noting that two weeks earlier, for reasons that remain obscure some three and a half centuries later, Leibniz had been denied his doctorate in law by the faculty of the University of Leipzig, despite having recently published his first book, On the Art of Combinations. Upon hearing the verdict he had gone for a walk on the outskirts of town, in the Rosental woods, where, while staring at the trunk of a tree, he was struck for the first time—as he recalled decades afterward in a letter to the French skeptic Simon Foucher—by the “calamitous” implications of the philosophy of Descartes, who had severed the mind from the world, transformed the world into a gargantuan machine, and made the mind doubt everything but its own existence. For a brief moment in his nineteenth year Leibniz lost his faith in reason. The next fortnight finds him en route to Bohemia. I imagine him trudging through that summer snow in search not only of material for publication but of a happier and more harmonious relationship between mind and world.