Hume's Conditions for Causation: Further to Gray and Imlay

119. HUME'S CONDITIONS FOR' CAUSATION: FURTHER TO GRAY AND IMLAY As part of his second proof of the existence of God, Descartes in Meditations III argues a causal premise derived from the nature of time. He argues it follows from the nature of time "that, in order to be conserved in each moment in which it endures, a substance has need of the same power and action as would be necessary to produce and create it anew, supposing it did not yet exist; so that the light of nature shows us clearly that the distinction between creation and conservation is solely a distinction of reason." The nature of time to which he refers allows only a finite divisibility into durationless moments, each of which is entirely independent of every other. In the ultimate analysis , nothing true of one moment is deducible from what is true of any other, even what happens to be eternally true. The doctrine of the creation of the eternal verities is of a piece with this conception of time, and following with it from the conception of the divinity as sheer omnipotence, points to Hume's view that experience is the only guide to the world. It would seem to be Descartes' view, that nothing at a given time can stand in the necessary relation it must have to be a cause of something at another time; or, only something outside time can be a cause, for whose operation things in time can serve as but occasions. To what extent this dialectic in fact led to later occasionalist views is an historical question we need not consider. My only suggestion here concerns Hume's réponse to the occasionalists . With all but psychological necessity eliminated from his analysis of causation, Hume effectively argues the familiar case that occasional causes are the only causes by arguing the finite divisibility of time. In the literature only Laporte has held that for Descartes time is infinitely divisible and in this sense continuous. The separability of the parts of time, he 120. thought, suffice for their independence and contingency. But if time is continuous, its parts are inseparable; as Gueroult correctly observes, by discontinuity is meant con2 tingence, independence and separability. In addition, if a moment had duration, light would not be propagated instant aneously, thus according to Descartes upsetting his entire 3 physics. Gueroult maintains, rather, that Descartes' view of time is determined by his view of motion. Whatever the historical and logical priorities, there clearly is a connection between the above and what Bergson called the cinematographic conception of motion as a succession of static objects. It is a conception that precludes events as such. Motion occurs only in time, never at the moment, and occurs as a result of the re-creation of matter with regularly differing spatial relations. Due to metaphysical consideration expressed in theological terms, especially with reference to the immutability and simplicity of divine ways, this recreation of matter is constrained in certain ways, some of which we pick out as conditions for what was later called occasional causation. Put very simply, only what is constantly conjoined can stand in this relation; and that there should be instances of constant conjunction follows from the metaphysical considerations. With Hume's elimination of these metaphysical considerations, the status of the conditions , which he takes over as conditions for causation simpliciter, becomes problematic. But a recent challenge to Hume's program is still more problematic. The contention is that there is a case in which Hume's conditions necessary fo constant conjunction cannot all be satisfied. Even worse, i is a case in which his analysis ought to be conspicuously successful, viz. collision, which Hume like Descartes con4 ceives in cinematographic terms. The aim of this paper is to show that Hume's analysis stands against the challenge. Consider the following diagram which illustrates the positions (A3, A_...) of two balls (x,y) at successive moments (t_, t.,...)· 121. A3 A2 A1 A B -B1 B2 B3 fc0 T T T ©© © G®©T©T h fc3 fc4 fc5 H Robert Gray's thesis is that in at least one case of causation, collision which results in...