CARTESIANISM, the philosophy of Rene Descartes (q.v.) and his school, among whom may be reckoned Geulincx, Malebranche, Arnauld, Nicole, and even many who stood out side the circle of professional philosophers like Bossuet and Finelon. Spinoza and Leibnitz have much in common with Descartes in stand point and method, but the divergencies of their systems from his are too great to justify us in classifying them as Cartesians. Among the many noteworthy points in Descartes' system we may mention the deliberate determination to doubt everything that could intelligibly be called in question. This was not scepticism, but a principle of method that he employed to enable him to reach something absolutely cer tain. This basal fact he found in the famous proposition, "I think, therefore I am* (Cogito ergo sum, je posse done je suis). No doubt could shake the certainty the ego possesses of its own existence. Moreover, Descartes finds in consciousness certain ideas that are not due to experience and not the product of the imag ination. These ideas he pronounces connate, original possessions of the mind. Among them the chief is that of the conception of God as an infinite and all-perfect being. Now the presence of this idea, Descartes argues, proves the actual existence of God as its cause, for no finite being can be the author of the idea of infinity. Having thus established the existence of God, Descartes maintains that the veracity of God warrants us in believing that whatever we perceive through the medium of clear and distinct ideas must be true. Adopting the traditional notion of substance he holds that besides the infinite substance, God, there are two finite created • substances, namely, matter or extended substance, and mind or thinking substance. These have no attributes in com mon, and are absolutely opposed to each other. Thus his philosophy is a Dualism (q.v.). In the human organism these two substances are united. The soul has its seat in the pineal gland, and at this point receives influences from the body, and in turn controls and governs the direction of bodily movements. Descartes' ac
count of the physical world is given in terms of the mechanical theory, the principles of which he was one of the earliest thinkers to formulate clearly. All bodies are extended, figured, substances, without any internal prop erties or differences. Everything that takes place in the physical world consists in the movement of an extended body. Thus the sciences of physical nature can be compre hended in a mathematical physics which has for its data the size, shape, velocity (amount of motion) and direction of the various bodies of which the physical world is composed. God at the beginning created bodies with a fixed quantity of motion and rest ; and since God is unchanging, this amount is subject to no in crease or diminution. From this statement, which is couched in scholastic language, has come, through a closer analysis of conceptions, the modern principle of the conservation of energy. Descartes' view of the relation of body and mind was not satisfactory even to the members of his own school, and led to the doctrine of Occasionalism and with Spinoza to a thorough-going Parallelism (q.v.). He also left to his successors the further elaboration of the problem regarding the relation of the one infinite substance, God, to the two created sub stances. In the 'Passions de lame) he made an important contribution to the psychology of the emotions, deriving all forms of emotional experience from the six primary emotions, wonder, love, hate, desire, joy and grief.
Bibliography.— Boater, 'Histoire de la Philosophic Cartesienne) (3d ed., Paris 1868) ; Descartes, 'Discours de la mithode); 'Medita tions on the First Philosophy,' and 'Principles of Philosophy) (in Veitch's or Torrey's trans lation) ; Fisher, Kuno, 'Descartes and His School> (English translation by J. Gordy) ; Mahaffy, J. P., 'Descartes) (in 'Blacicwood Philosophical Classics)) ; Smith, Norman, in the Cartesian Philosophy.)