1. Mind and matter, consciousness and existence, Descartes had fixed in the farthest separation from each other. Both, with him, are substances, independent powers, reciprocally excluding oppositions. Mind (i. e. in his view the simple self, the Ego) he regarded as essentially the abstraction from the sensuous, the distinguishing itself from matter and the separating of matter from itself; matter was essentially the complete opposition to thought. If the relation of these two powers be as has been given, then the question arises, how can there ever be a filiation (Rapport) between them? How, on the one hand, can the affections of the body work upon the soul, and on the other hand, how can the volition of the soul direct the body, if the two are absolutely distinct and opposed to each other? At this point, Arnold Geulincx (a disciple of Descartes, born at Antwerp 1625, and died as professor of philosophy at Leyden 1669) took up the Cartesian system, and endeavored to give it a greater logical perfection. According to Geulincx neither the soul works immediately upon the body, nor the body immediately upon the soul. Certainly not the former: for though I can determine and move my body in many respects arbitrarily, yet I am not the cause of this movement; for I know not how it happens, I know not in what manner motion is communicated from my brain to the different parts of my body, and it is impossible that I should do that in respect of which I cannot see how it is done. But if I cannot produce motion in my body, much less can I do this outside of my body. I am therefore simply a contemplator of the world; the only act which is peculiarly mine is contemplation. But even this contemplation arises in a singular manner. For if we ask how we obtain our observations of the external world, we find it impossible that the external world should directly give them to us. For however much we may say that, e. g. in the act of seeing, the external objects produce an image in my eye or an impression in my brain as in wax, yet this impression or picture is after all only something corporeal or material, and cannot therefore come into my mind, which is absolutely distinct from every thing material. There remains, therefore, only that we seek the mediation of the two sides in God. It is God alone who can unite the outer with the inner, and the inner with the outer; who can make the outer phenomena to become inner representations or notions of the mind; who can thus bring the world within the mind’s observation, and the inner determinations of the will outward into deed. Hence every working, every act which unites the outer and inner, which brings the mind and the world into connection, is neither a working of the mind nor of the world, but only an immediate working of God. The movement of my limbs does not follow from my will, but only because it is the will of God that these movements should follow when I will. My will is an occasion by which God moves my body—an affection of my body is an occasion by which God brings within me a representation of the external world: the one is only the occasional cause of the other (hence the name occasionalism). My will, however, does not move God to move my limbs, but he who has imparted motion to matter and given it its laws, created also my will, and has so connected together the most diverse things, the movement of matter and the arbitrium of my will, that when my will puts forth a volition, such a motion follows as it wills, and the motion follows the volition without any interaction or physical influence exerted by the one upon the other. But just as it is with two clocks which go exactly alike, the one striking precisely as the other, their harmony is not the result of any reciprocal interacting, but follows because both have been fashioned and directed alike,—so is it with the movements of the body and the will, they harmonize only through that exalted artist who has in this ineffable way connected them together. We see from this that Geulincx has carried to its limit the dualistic basis of Descartes. While Descartes called the union of mind and matter a conjunction through power, Geulincx named it a miracle. There is consequently in this view no immanent, but only a transcendent mediation possible.

2. Closely connected with this view of Geulincx, and at the same time a real consequence and a wider development of the Cartesian philosophizing, is the philosophic standpoint of Nicolas Malebranche. He was born at Paris in 1638, chosen a member of the “CongrÉgation de l’oratoire” in his twenty-second year, won over to philosophy through the writings of Descartes, and died, after numerous feuds with theological opposers, in 1715.

Malebranche started with the Cartesian view of the relation between mind and matter. Both are strictly distinct from each other, and in their essence opposed. How now does the mind, (i. e. the Ego) gain a knowledge of the external world and have ideas of corporeal things? For it comes to know things only by means of ideas,—not through itself, not immediately. Now the mind can neither gain these ideas from itself, nor from the things themselves. Not from itself, for it is absolutely opposed to the bodily world, and hence has no capacity to idealize, to spiritualize material things, though they must become spiritualized before they can be introduced to the mind; in a word, the mind, which in relation to the material world is only an opposition, has no power to destroy this opposition. Just as little has the mind derived these ideas from things: for matter is not visible through itself, but rather as antithetic to mind is it that which is absolutely unintelligible, and which cannot be idealized, that which is absolutely without light and clearness.—It only remains, therefore, that the mind beholds things in a third that stands above the opposition of the two, viz., God. God, as the absolute substance, is the absolute ideality, the infinite power to spiritualize all things. Material things have no real opposition for God, to him they are no impenetrable darkness, but an ideal existence; all things are in him spiritually and ideally; the whole world, as intellectual or ideal, is God. God is, therefore, the higher mean between the Ego and the external world. In him we behold ideas, we being so strictly united with him, that he may properly be called the place of minds.

The philosophy of Malebranche, whose simple thought is this, that we know and see all things in God,—shows itself, like the occasionalism of Geulincx, to be a peculiar attempt to stand upon the basis of the Cartesian philosophy, and with its fundamental thought to overcome its dualism.

3. Two defects or inner contradictions have manifested themselves in the philosophy of Descartes. He had considered mind and matter as substances, each one of which excluded the other from itself, and had sought a mediation of the two. But with such conditions no mediation other than an external one is possible. If thought and existence are each one substance, then can they only negate and exclude each other. Unnatural theories, like those which have been mentioned, are the inevitable result of this. The simplest way out of the difficulty is to give up the principle first assumed, to strip off their independence from the two opposites, and instead of regarding them as substances, view them as accidents of one substance. This way of escape is moreover indicated by a particular circumstance. According to Descartes, God is the infinite substance, the peculiar substance in the proper sense of the word. Mind and matter are indeed substances, but only in relation to each other; in relation to God they are dependent, and not substances. This is, strictly taken, a contradiction. The true consequence were rather to say that neither the Ego (i. e. the individual thinking) nor the material things are independent, but that this can be predicated only of the one substance, God; this substance alone has a real being, and all the being which belongs to individual essences these latter possess not as a substantial being, but only as accidents of the one only true and real substance. Malebranche approached this consequence. With him the bodily world is ideally at least resolved and made to sink in God, in whom are the eternal archetypes of all things. But Spinoza has most decidedly and logically adopted this consequence, and affirmed the accidence of all individual being and the exclusive substantiality of God alone. His system is the perfection and the truth of the Cartesian.