Kant is not merely concerned to arrive at the truth or falsity of particular metaphysical principles. In inquiring how metaphysics is possible, Kant is trying primarily not to account for the existence of the philosophic endeavour but to remedy the plight in which it finds itself. Ernst Cassirer writes, Kant's 'foundational ontology' first appears in the Transcendental Dialectic, in the Critique of Practical Reason and in the Critique of Judgment. The two leading commentators on Kant in English, Paton and Kemp Smith, are well aware that Kant does not conclude that metaphysics is impossible. All representatives of 'neo-Kantianism' have been agreed on one point: that the heart of Kant's system is to be sought in his theory of knowledge, that the fact of science and its possibility constitute the beginning and aim of Kant's putting of the problem. Heidegger is correct in holding that Kant is concerned with philosophy as a fact of human existence.