Joseph Marechal, who became one of the most important figures in the twentieth-century revival of the thought of St. Thomas Aquinas, set for himself an ambitious intellectual project. His goal was to demonstrate that the realist theory of knowledge first enunciated by Aristotle in the ancient world and developed by Aquinas in the thirteenth century is the key to a coherent philosophy of man and being. According to Marechal, once late medieval philosophy moved away from Aquinas's epistemological foundations, no longer could it construct a satisfactory unity of knowledge, man, and being. Thus modern Western philosophers, specifically Descartes, began their quest to elaborate an adequate intellectual account of human experience on the basis of a flawed philosophical legacy.