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 PHILOSOPHY 441 modern idealism. Like Campanella, he had passed through an experience of skepticism, but he was not satisfied to overcome doubt by the testimony of the senses. His object was to constitute philosophy a demonstrable science. To this end he begins with doubt. He admits the illusory nature of the pheno- menal. The basis of valid knowledge is that consciousness which gives evidence of the ego and the non-ego, spirit and matter, subject and object: Cogito, ergo sum. His theistic argument has already been cited. He made clearness and distinctness the criteria of true thought. As the certainty of the self-conscious spirit was the foundation of his philosophy, the superiority of mind to matter and the pe- culiar idealism of his system was the necessary result. By his doctrine of assistentia he ac- counts for" the communion between soul and body. Fatal as the speculations of Descartes were to the lingering authority of scholasti- cism, they were weakened by their connection with groundless scientific theories. Pascal and Huet gave evidence of more sympathy with his original doubt than his philosophical assurance. Gassendi was one of his opponents, and Geu- lincx and Malebranche materially modified his system. Malebranche, followed to some extent by John Norris of Bemerton, indulged in mys- tic tendencies, making knowledge the result of the union of the soul with God, or of a con- stant divine indwelling by which divine ideas are made apprehensible to us. The most preg- nant apophthegm of his philosophy was, "We see all things in God. The theory of Descartes supplied Spinoza with a scientific form for his system. From the postulates of substance and causality, he deduces his conclusions after the mathematical method. His postulate of sub- stance is that of one absolute essence, an in- finite being, with infinite attributes of exten- sion and thought. In this unity the dualism of mind and matter is swallowed up. Finite beings are only modes of the infinite attri- butes. All exist in the Deity, their inherent cause, natura naturans, and all necessarily pro- ceed therefrom. Here is the base of Spinoza's imposing pantheism and universal necessity. Leibnitz, a universal scholar and an acute critic, reached his ideal standpoint by spirit- ualizing matter, and increasing to infinitude the number of substances. He identifies mat- ter with active force, and in his universe com- posed of u monads" bestows perception, more or less distinct, upon every atom, each of which in its own way represents and reflects the universe. To meet the objection that each monad has its own law, and that it is im- practicable to combine it with another, as soul with body, over which it can have no con- trol, he devised his doctrine of preestablished harmony. God is the mona* primitiva, from whom all finite monads are derived ; and be- sides these and phenomena, which are percep- tions of monads, nothing exists. In contend- ing for certain necessary truths, not mathema- tical but metaphysical, which must be sought in the soul itself, and not certified by experi- ment, Leibnitz prepared the way for the cate- gories of Kant. Wolf rejected indeed his no- tions of monads and preestablished harmony, retaining his optimism and determinism, and sketching out for the first time a complete encyclopaedia of the philosophical sciences. In Germany and France the influence of Locke was powerfully felt. In the latter country Con- dillac reduced Locke's two sources of knowl- edge to sensation alone, and in transformed sensations explained all the high attainments of human intelligence developed in his ideal statue. His system fell in with the French reaction of his time, and was in sympathy with the theory of self-love advanced by Hel- vetius, the moralist of sensationalism. An- other stage of progress was reached in the materialistic atheism of La Mettrie and D'Hol- bach. To this result the writings of Hume had contributed, but in England and Scotland the philosophy of Locke had not been sub- jected altogether to an exclusively sensualistic interpretation. In rejecting innate ideas, and positing qualities, as color and sound, in the perceiving subject, he prepared the way for Berkeley to assert that only minds and their ideas exist, and that the permanence of ideas is the proof of an Eternal Mind to which they are uninterruptedly present. But this posi- tion, in connection with Locke's sensational- ism and empiricism, gave occasion to the skep- tical philosophy of Hume, who applied the principles thus evolved, denying the possibil- ity of knowing the nature and mode of the objective connection between cause and effect, and thus disputing the philosophical legitima- cy of the attempt to transcend by means of the causal idea the field of experience, or thus conclude the existence of God and the immor- tality of the soul. This skepticism, destruc- tive not only of speculative philosophy, but of the foundations of all real knowledge, was combated in Scotland by Keid, who sought to establish against it his " philosophy of common sense," in which he rejected representative ideas; while in Germany it stimulated Kant to an examination of the foundations and con- ditions of human knowledge. Educated in the school of Wolf, but sympathizing more with Descartes than with Leibnitz, he produced his "Critique of Pure Keason," in which he as- sumes that our first step must be to scruti- nize the processes of the mind, and thus de- termine, not what is the nature of things, but what can man know. All cognition is the product of two factors, the cognizing subject and the cognized object. One of these con- tributes the matter, the other gives it form. Perceptions without notions are blind, and notions without perceptions are void. Yet we do not know things as they are in them- selves, but in their, perceptions, while the forms native to the mind, the categories on which thought is conditioned, add to the given