Occasionalism (Latin occasio) is the metaphysical theory which maintains that finite things have no efficient causality of their own, but that whatever happens in the world is caused by God, creatures being merely the occasions of the Divine activity. The occasion is that which by its presence brings about the action of the efficient cause. This it can do as final cause by alluring the efficient cause to act, or as secondary efficient cause by impelling the primary cause to do what would otherwise be left undone. Occasionalism was foreshadowed in Greek philosophy in the doctrine of the Stoics who regarded God as pervading nature and determining the actions of all beings through the fundamental instinct of self-preservation. It appeared openly in the Arabian thought of the Middle Ages (cf. Stein, II, 193-245 infra); but its full development is found only in modern philosophy, as an outgrowth of the Cartesian doctrine of the relation between body and mind. According to Descartes the essence of the soul is thought, and the essence of the body extension. Body and soul therefore have nothing in common. How then do they interact? Descartes himself tried to solve this problem by attributing to the soul the power of directing the movements of the body. But this idea conflicted with the doctrine involved in his denial of any immediate interaction between body and mind. The first step toward a solution was taken by Johannes Clauberg (1625-65). According to him all the phenomena of the outside world are modes of motion and are caused by God. When therefore the mind seems to have acted upon the outside world, it is a pure delusion. The soul, however, can cause its own mental processes, which have nothing in common with matter and its modes of action. Matter, on the other hand, cannot act upon mind. The presence of certain changes in the bodily organism is the occasion whereupon the soul produces the corresponding ideas at this particular time rather than any other. To the soul Clauberg also attributes the power of influencing by means of the will the movements of the body. The Occasionalism of Clauberg is different from that of later members of the school; with him the soul is the cause which is occasioned to act—with the others it is God.
Louis de la Forge (Tractatus de mente humana, 1666) is regarded by some as the real father of Occasionalism. His starting point was the problem of the relation between energy and matter. Following the Cartesian method, he argued that what cannot be clearly and distinctly conceived cannot be held as true. We can form no clear idea of the attraction exerted by one body on another at a distance nor of the energy that moves a body from one place to another. Such an energy must be something totally different from matter, which is absolutely inert; the union between matter and energy is inconceivable. Matter then, cannot be the cause of the physical phenomena; these must be produced by God, the first, universal, and total cause of all motion. In his theory of the union between body and soul, de la Forge approached the later Leibnizian doctrine of a pre-established harmony. God must have willed and brought about the union between body and soul, therefore He willed to do all that is necessary to perfect this union. The union between body and mind involves the appearance of thoughts in consciousness at the presence of bodily activities and the sequence of bodily movements to carry out the ideas of the mind. God willing the union between body and mind willed also to produce, as first and universal cause, the thoughts that should correspond to the organic movements of sensation, and the movements which follow upon the presence of some conscious processes. But there are other movements for which the soul itself is responsible as efficient cause, and these are the effects of the spontaneous activity of our free will.
The Occasionalism of Arnold Geulincx (1624-1669) is ethical rather than cosmological in its inception. The first tract of his “Ethics” (Land’s ed. of the Opera, The Hague, 1891-93) is a study of what he termed the cardinal virtues. These are not prudence, temperance, justice, and fortitude. Virtue according to Geulincx is the love of God and of Reason (III, 16-17; 29). The cardinal virtues are the properties of virtue which immediately flow from its very essence and have nothing to do with anything external. These properties are diligence, obedience, justice, humility (III, 17). The division which Geulincx makes of humility is one of fundamental importance in his philosophy. It divides his view of the world into two parts—one, the understanding of our relation to the world, and the other, the concept of our relation to God. Humility consists in the knowledge of self and the forsaking of self. I find in myself nothing that is my own but to know and to will. I therefore must be conscious of all that I do, and that of which I am not conscious is not the product of my own causality. Hence the universal principle of causality—quod nescis quo modo fiat, non facis— if you do not know how a thing is done then you do not do it. Since then, the movements of my body take place without my knowing how the nervous impulse passes to the muscles and there causes them to contract I do not cause my own bodily actions. “I am therefore a mere spectator of this machine. In it I form naught and renew naught, I neither make anything here nor destroy it. Everything is the work of someone else” (III, 33). This one is the Deity who sees and knows all things. The second part of Geulincx’s philosophy is connected with Occasionalism as the effect with the cause. Its guiding principle is: Where you can do nothing there also you should desire nothing (III, 222). This leads to mysticism and asceticism which however must not be taken too seriously for it is tempered by the obligation of caring for the body and propagating the species.
Nicolas Malebranche (q.v.) developed Occasionalism to its uttermost limit, approaching so near to Pantheism that he himself remarked that the difference between himself and Spinoza was that he taught that the universe was in God and that Spinoza said that God was in the universe. Starting out with the Cartesian doctrine, that the essence of the soul is thought and that of matter is extension, he sought to prove that creatures have no causality of their own. Experience seems to tell us that one body acts upon another, but all that we know is that the movement of one body follows upon that of another. We have no experience of one body causing the movement of another. Therefore, says Malebranche, one body cannot act upon another. By a similar argument he attempts to prove that body cannot act upon mind. Since experience can tell us only that a sensation follows upon the stimulus, therefore the stimulus is not the cause of the sensation. He uses the argument of Geulincx to prove that mind cannot act upon body. Not only is there no interaction between body and mind, and between one body and another, but there is no causality within the mind itself. Our sensations, for example, are not caused by bodies, and are independent of ourselves. Therefore they must be produced by some higher being. Our ideas cannot be created by the mind. Neither can they be copied from a present object, for one would have first to perceive the object in order to copy it, after which the production of an idea would be superfluous. Our ideas cannot be all possessed as complete products from the beginning, because it is a fact that the mind goes through a process of gradual development. Nor can the mind possess a faculty that produces by a sufficient causality its own ideas, because it would have to produce also the ideas of extended bodies and extension is excluded from the essence of the mind and therefore from the scope of its causal efficiency. If then there is no way of accounting for ideas and sensations either by the efficiency of the mind itself or by that of the outside world they must be produced by God, the infinite, omnipresent, universal Cause. God knows all things because He produced all things. Therefore the ideas of all things are in God, and on account of His most intimate union with our souls the spirit can see what is in God.
Among the Occasionalists is also mentioned R. H. Lotze (1817-81). His Occasionalism is really only a statement that we are ignorant of any interaction between body and mind, or between one material thing and another. He is not an Occasionalist in the meta-physical sense of the word. In estimating the value of the Occasionalistic position we must realize that it sprang from a twofold problem, the interaction of body and mind and the relation of body, mind, and world to God, the first cause of all. The success of the Occasionalist answer to the first difficulty was dependent upon the fate of the Cartesian philosophy. If man is composed of two absolutely distinct substances that have nothing in common, then the conclusion of the Occasionalists is logically necessary and there is no interaction between body and mind. What appears to be such must be due to the efficient causality of some external being. This difficulty was not felt so keenly in Scholastic philosophy because of the doctrine of matter and form, which explains the relation of body and soul as that of two incomplete but complementary substances. Very soon, too, it began to lose its hold upon modern thought. For Cartesianism led, on the one hand, to a Monistic Spiritualism and, on the other, to Materialism. In either case the very foundations of Occasionalism were undermined. In its attempt to solve the second difficulty, Occasionalism did not meet with any particular success. From its doctrine of the relation between body and soul it argued to what must be the relation between God and the creature in general. The superstructure could not stand without the foundation.
THOMAS V. MOORE