Descartes, Occasionalist

According to Norman Kemp Smith (Problems in the Cartesian Philosophy), “The great achievement of Galileo and Descartes in physical science consisted in a new theory of motion. Whereas by the Greek Atomists and by Aristotle motion was anthropomorphically conceived, as, like human activity, coming into being, exhausting itself in exercise against obstacles, and ceasing to be—the fleeting activity of a matter that is alone abiding ; with Galileo and Descartes it asserts its full rights. It is, they show, in its ingenerable, indestructible nature, as different from human activity as matter is from mind” (69).

Matter and motion are distinct, but in his work on physics, Descartes insists that they are “equally substantial, since they are equally ingenerable out of nothing, and equally in destructible.” This was a revolutionary breakthrought: “In Greek science the differences between natural phenomena are ascribed to differences in matter, either to differences between atoms or to differences between elements : in Descartes’ philosophy of nature, as in modern science, they are ascribed to differences of motion. Matter becomes the mere vehicle of motion, and motion the all-important reality” (70).

This means that it’s inaccurate to speak of Cartesian “dualism.” We should instead speak of a triism: “Descartes’ analysis of the real lands him not in a dualism, but in a trinity, and in a trinity one of whose elements mediates between the other two. Motion, like matter, is unconscious, but also, like mind, is unextended, immaterial, and active. The fictitious dualism conceals a purely relative trinity of the three substantial realities, matter, motion, and mind” (70).

Yet Descartes’s philosophy is inconsistent with his physics. When he philosophizes on physics, motion is not substantial but a “mode” of matter, since matter is conceivable apart from motion but motion is inconceivable apart from matter moved. And this, Smith argues, leads Descartes into an affirmation of occasionalism. Descartes cannot, he admits, prove the necessity of existence, and thus every thing existing is “contingent, that is to say, as unaccountable by reason, and therefore, in Descartes’ way of stating it, as due to the arbitrary will of God. But, further, not only is each finite thing contingent in its origin, so also is its continued existence, that also being inexplicable from its essence. Since each moment of time is distinct from every other, the persistence of an existence from one moment on to another demands an explanation as much as its first origin, and yet again none can be given, save only the will of God. Persistence in existence, says Descartes, is in all essentials perpetual and unceasing recreation” (72-3). Causation too is inexplicable, and so is dependent upon God: “If finite bodies have so little hold on reality that they require at each moment to be recreated, they cannot be capable of causing changes in one another” (73).

Thus, the “most extreme occasionalism is . . . the outcome of Descartes^ metaphysics. The continuity of existence, and therefore the continuity of time and of causal connection in time, is broken up by his atomistic doctrine of essence into a series of detached events upheld in their existence and connection by God” (74). This is inherent in his understanding of motion, which he sometimes describes as a “mode” of matter. This leaves him with unhappy alternatives: If motion is a mode (like shape), it cannot be transferred from one things to another, and so secondary causation evaporates; or each body has the capacity to create new motion when it impacts other bodies, since it cannot transfer its motion. To escape the dilemma, he equivocates on motion: While motion is a mode of matter, Descartes also “inconsistently continues to conceive it as a separate entity, distinct both from God who has created it, and from the matter in which it may exist in varying quantities” (76).

Challenged by Henry More for his inconsistency, Descartes “admits the distinction between motion as mere transference and motion in the sense of moving force. While the first is a mere mode of matter, the second comes from God who continuously preserves the same amount of transference (translatio) in matter, as He has set into it at the first moment of Creation” (78). In short, he opts for occasionalism.