=The Relation of the Occasionalists and Spinoza to Descartes.= The development of the doctrines of the Occasionalists and Spinoza from Descartes was an attempt to make clear the conception of _substance_. Since substance was the most important scholastic category, it is easy to see why Spinoza’s teaching became thoroughly scholastic. Descartes had used the term “substance” in a very loose way to apply to God as infinite, and to minds and bodies as finite. He speaks of God as the only substance, and yet of consciousness and bodies as created substances. Such ambiguity must be overcome, if a philosophy which prided itself on making everything “clear and distinct” was to stand. Descartes had fallen short of justifying his attempt to put metaphysics completely upon a mathematical basis, although this had been his original problem. The obscurity of the spiritual world still remained, because Descartes had left the concept of the spiritual substance undefined. The world of the spirit was still an unknown country. The spiritual substance had not been made clear and distinct, and there still remained the ontological problem of the relation between mind and matter, and the psychological problem of the relation between the individual soul and its body. Descartes had, however, defined clearly the concept of the substance of matter――the substance with which the natural scientist works. He had accomplished this, to be sure, by destroying the essential distinctions between material things. A “thing” is essentially a substance in which many qualities inhere, _e. g._ a piece of sugar having whiteness, sweetness, etc. Material substances were alike in that all were essentially extension. All else besides extension in any particular finite thing was a modification of extension. A lump of sugar was essentially the same as a lump of salt in that both were extension; the saltness, sweetness, etc., were secondary. Now this makes the nature of bodies very clear; and Descartes proposed to reduce the substance of the states of mind to the same clearness, but he did not do it. He was interested in natural science and he developed his rationalism only with reference to matter. Bodies are parts of space or corpuscles, which are mathematically infinitely divisible, but perceptually are not further divisible. As far as he went, Descartes was clear enough.