quently than the others, and in the meaning given to it by the author appears to express the philosopher's thought most clearly. No knowledge, Descartes holds, is more certain than the existence of a thinking subject, and this is based on such an immediate perception or intuition. On this truth as the fundamental proposition the whole chain of reasoning is based; every succeeding deduction must stand the test of the criterion, if it is to have any validity whatever. I also mention the Cartesian argument for the existence of God as bearing out M. Twardowski's statement. If the clearness and distinctness of the idea formed the criterion, the mere presence in the mind of such an idea of God would be sufficient evidence of his reality. But Descartes' proof is not merely ontological, it is anthropological. There is present in the soul an idea of God, which possesses more reality than all other ideas. It is clearly manifest that everything must have its cause, and that the efficient cause must have at least as much reality as the effect. Therefore God exists (Med. III, Pr. ph., I, 17). In the entire chain of reasoning no proposition is accepted as true unless it meets the requirements of the regula generalis.
M. Twardowski's book is as valuable as it is short. In calling attention to a distinction which has been almost universally ignored, he brings us much nearer to a clear understanding of Cartesian epistemology than we were before.
This volume forms the natural sequel to the author's volumes on Ancient and Modern Philosophy, and The Metaphysic and Psychology of the Unknowable. It is also intended to be introductory to two already partially accomplished works, one bearing on the metaphysic and psychology of the knowable, and the other on the monism which has been the chimerical pursuit of philosophers of all ages.
M. de Roberty thinks that the philosophy of the nineteenth century can be reduced to the three forms of Criticism, Positivism, and Evolutionism. He suggests that the origin of Criticism is to be found in Idealism, as critical philosophy arrives at idealities or abstractions such as the Infinite. The origin of Positivism is to be sought in Materialism as the dogmatic reaction against Idealism; and the origin of Evolutionism is to be sought in Sensationalism which, in the hands of physiologists and empiricists, led to excursions into biological science. As to this, one would wish that the author had done Criticism the justice of regarding it as predisposed against the excesses of all dogmatic
