Nathan Tarcov recently pointed out in these pages that much nonsense has been written about the supposed influence of the late Leo Strauss on American foreign policy.¹1. “Will the Real Leo Strauss Please Stand Up?” The American Interest (Autumn 2006). This nonsense takes its cue not from Strauss’ own writings, but from the voluminous interpretations of his students—and students of his students—who claim Strauss’ legacy in what has become a secular version of apostolic succession. It is therefore a bit curious that no one seems to have wondered about Strauss’ own teachers. As it happens, Strauss’ doctoral dissertation adviser and an important early influence on him was one of the greatest philosophers of the 20th century: Ernst Cassirer.

Like Strauss, Cassirer was a German Jew. Like Strauss, Cassirer left Germany and eventually ended up in America, finding a home at a great American university—Strauss at Chicago, Cassirer at Columbia. But unlike Strauss, no one has ever accused Cassirer of having meddled from beyond the grave into the portentous affairs of American foreign policy. That is partly because Cassirer was not especially interested in politics, and partly because, except for academic philosophers and the occasional library-grazing intellectual, very few Americans have ever heard of Ernst Cassirer. That’s too bad, for he is still worth reading today. Indeed, he is perhaps the ideal philosopher for Americans in the tumultuous times in which we live.

First of all, Cassirer is the quintessential philosopher of freedom. His entire philosophical frame of reference focused on the irreducible value of freedom, and his entire professional life was devoted in both word and deed to its spread. Second, Cassirer was an indefatigable optimist. With Hegel and against Nietzsche in the great contest of his German-language philosophical forebears, he believed that history and humanity had a direction, and that it was a positive one. And third, Cassirer was both an empiricist and a humanist. He believed that actual human history and human nature in all their diversity, not ethereal speculation and armchair cosmologizing, composed the right data set for philosophy.

Empiricism, however, is not the same as positivism. While Cassirer saw the challenge of understanding real people in the real world as the way to philosophical truth, he was no materialist. Indeed, Cassirer was one of the giants in a group of 20th-century German philosophers known as the neo-Kantians. Neo-Kantians, like Immanuel Kant himself, rejected both materialism and transcendentalism as means to ground either philosophical understanding or moral behavior. Consciousness itself, therefore, became the main object of study; inquiries into language, sociology, anthropology, psychology and child development interested them most. Of all the neo-Kantians, Cassirer yearned most...