In this translation of Etienne Gilson's well known work L'esprit de la philosophie medievale, he undertakes the task of defining the spirit of mediaeval philosophy. Gilson asks whether we can form the concept of a Christian philosophy and, second, whether mediaeval philosophy is not precisely its most adequate historical expression. He maintains that the spirit of mediaeval philosophy is the spirit of Christianity penetrating the Greek tradition, working within it, and drawing out of it a certain view of the world that is specifically Christian. To support his hypothesis, Gilson examines mediaeval thought in its nascent state, at that precise point where the Judeo-Christian graft was inserted into the Hellenic tradition. Gilson's demonstration is purely historical and occasionally theoretical in suggesting how doctrines that satisfied our predecessors for so many centuries may still be found conceivable today.