The philosophical premise, concepts, and approaches of transcendental Thomism have clearly been the most important source of Catholic theological and philosophical development in the twentieth century. But for this school the monumental work of Karl Rahner and of Bernard Lonergan to mention two of the most distinguished instances is inconceivable in its present form. The methodical importance and radical mode of the movement make it doubly regrettable that until now the primary work of Joseph Marechal , the funder of the school - the first to work out the connections between the Thomistic metaphysics of knowledge and transcendental philosophy - has not been available in English.