The question concerning the substantiality of mind and matter in relation to God, is involved from the very beginning in this latter problem, "How is the appearance of interaction between the two to be explained without detriment to their substantiality in relation to each other?" The denial of the reciprocal dependence of matter and spirit leads to sharper accentuation of their common dependence upon God. Thus occasionalism forms the transition to the pantheism of Spinoza, Geulincx emphasizing the non-substantiality of spirits, and Malebranche the non-substantiality of bodies, while Spinoza combines and intensifies both. And yet history was not obliging enough to carry out this convenient and agreeable scheme of development with chronological accuracy, for she had Spinoza complete his pantheism _before_ Malebranche had prepared the way. The relation which was noted in the case of Bruno and Campanella is here repeated: the earlier thinker assumes the more advanced position, while the later one seems backward in comparison; and that which, viewed from the standpoint of the question itself, may be considered a transition link, is historically to be taken as a reaction against the excessive prosecution of a line of thought which, up to a certain point, had been followed by the one who now shrinks back from its extreme consequences. The course of philosophy takes first a theological direction in the earlier occasionalists, then a metaphysical (naturalistic) trend in Spinoza, to renew finally, in Malebranche, the first of these movements in opposition to the second. The Cartesian school, as a whole, however, exhibits a tendency toward mysticism, which was concealed to a greater or less extent by the rationalistic need for clear concepts, but never entirely suppressed.