The Philosophy of David Hume I : On His Theory of Causation

Here I should like to explain the fundamental ideas which I made use of in my paper to disentangle the complication involved in the problem of the perceptibility of causation. It is a well-known fact that Hume denied that we could perceive any causation physical or mental, and that he believed that he succeeded in holding consistently the succession or regularity view of causality. But the results of A. Michotte's famous experiments on the perception of causality invite us to reconsider the problem and to reexamine the soundness of the regularity view itself. What has complicated the matter is the failure to distinguish between the individual causal connections which are asserted in singular causal statements and the nomic necessity of the connections of causes with their effects which are asserted in universal law-like causal statements. Hume denied that we could perceive causation, and he was right in that what he really denied was the perceptibility of nomic necessity of causation. Michotte affirmed that we could perceive causation, and he was right in that his real assertion was that we could perceive individual causal connections in some individual cases. First, let us suppose that before our eyes a billiard ball is rolling on the billiard table. Can we perceive the motion of the ball? If not, we can never come to assert that it is moving, however often we may have seen it. For however often we may have seen it, we can never come to find any new fact about it that did not appear at first. But we actually can often tell at a glance whether a body is in motion or at rest relatively to other bodies. Then we must be catching some perceptual clue, whatever it may be, that is sufficient for us to judge on the motion of bodies, and in this sense we can say that we perceive motion of bodies at least in some cases. Secondly, let us suppose that before our eyes a billiard ball A rolls on towards another billiard ball B and then hits it. Can we say that we perceive that the ball A hits the ball B? Should we say that we see merely the motion of the ball B immediately follow the impact on it of the ball A, but that since we already know by some other means than perception that in such a situation the impact of the ball A is the cause of the motion of the ball B, we can rightly judge that the ball A hit ball B on the basis of the perception of the mere succession of the two events? But in that case we must be given fairly sufficient perceptual clue for judging right on the causation, and we should have as good reason to say that we perceive causation as we have to say that we perceive motion of bodies. Or is it that causality consists in the mere regularity in succession of causes and effects? But in that case, by the very alleged nature of causality, we should perceive the causation of the motion of the ball B by the impact of the ball A, in perceiving the immediate succession of the former event to the latter. Finally, let us suppose that a billiard ball A is rolling towards another ball B but has not reached it yet. When we look at this scene, it is a trivial truth that we cannot perceive, though we can infer, that the ball A will hit the ball B.On the basis of these considerations, we can say that we perceive some individual causal connections; we perceive, for example, that that ball A now hits this ball B, or that that impact of the ball A now causes this motion of the ball B. But this is not to say that we can perceive nomic necessity implied in such universal law-like statements as ‘An impact of the ball A always causes a motion of the ball B’ or ‘On a smooth level table an impact of a ball in motion on another at rest always causes a motion of the latter.’ Nor is it to say that we perceive all individual causal connections. Suppose that a ball suddenly starts rolling on an apparently level table. In this case we do not perceive the causation of its motion; the table may slightly have been tilted, but this change of its condition is not perceived ex hypothesi. Hume denied the perceptibility of any causation physical or mental. According to him, we perceive merely successions of events, for example, an immediate succession of the motion of a ball B to the impact of another ball A. When and how do we then become able to judge on causation? It is, Hume replies, when we have formed in us a habit of association of ideas and come to feel determined to pass from the idea of the one event (the impact of the ball A) to the idea of the other (the motion of the ball B). But if we really do feel determined to pass from the one idea to the other, it will be a genuine perception of an individual mental or internal causation, for then we must be feeling that among many other impressions and ideas present to our mind this particular idea and nothing else is forcing our thought to pass to that particular idea and to nothing else. Hume did not realize that, because he failed to distinguish individual mental causal connection from nomic necessity of mental causation and was convinced of the imperceptibility of nomic necessity. Thus he believed that from the epistemological point of view he held consistently the regularity view of causality, and he was unaware that his admission of a feeling of ‘the determination of the mind’ or the compulsion of the association of ideas was nothing less than the admission of the immediate perception of an individual mental causal connection. Our interpretation of Hume's theory of causality discloses the fact that what he really did was to explain nomic causality in terms of perceptible indidividual mental connection, and enables us to explain away the ‘logical inconsistencies’ which are usually imputed to his theory of causality