No trait is more characteristic of contemporary philosophy in France than its continued fecundation by the physical and biological sciences. The divorce between philosophy and science that existed in the first half of last century is now regarded, by almost common consent, as an error of the great pre-war Unenlightenment. The ménage is rémonté; the vieilles traditions of Descartes and Pascal live again, though very transfigured. How long the alliance may endure, how and how much it may benefit both parties, it would be idle to prophesy. But it is significant that Boutroux and Bergson were compelled to devote much energy to acquiring a scientific competence, the one in mechanics, the other in biology. It is still more significant that a number of professional scientists (such as Milhaud, Duhem, Hannequin, Paul Tannery, Poincare, and Meyerson) should, with the passing of years, have contributed less to their sciences and increasingly to philosophy. This mutual invasion of territories has, indeed, become so considerable and enduring that philosophy in France is at present, for good or ill, almost wholly ‘philosophy of the sciences.’ It is now within this ‘internationalized’ neutral zone that the distinction between the epistemological and the ontological has to be drawn. Thus, Meyerson fairly represents the former emphasis, Bergson and Le Roy the latter. And if it is rare for one man to hold successively a chair in mathematics and a chair in philosophy, like Milhaud and Whitehead, rarer still is it for one man to hold both concurrently. But M. Edouard Le Roy has for many years lectured on mathematics and mechanics at the Faculte des Sciences in Paris; he has extended and modified Bergsonism from Bergson's former chair at the College de France.