Idealizing Hume

Idealizing Hume Alan Hausman and David Hausman Hume's explanation of our belief in the continuing existence of unperceived bodies is notoriously elusive.1 Stroud, for example, despairs that it is difficult to see how Hume's elaborate discussion of the constancy and coherence of perceptions explains the origin of the idea of continuing existence, let alone our belief that there are continually existing things.2 Yet Stroud, careful as he is, does not spot the key to the problem. It is not merely that constancy and coherence, the mainstays ofHume's four-part system, are obscure; rather, there is, we shall argue, a hidden assumption in the discussion which necessitates the construction of the system that embodies that obscurity. This hidden assumption is Hume's implicit idealism. That idealism,we shall show,fashionstheentirediscussionin"Ofscepticism with regard to the senses," as well as key passages in his discussion of the derivation of the idea of the self. Its main influence is on Hume's claims concerning the place of causal reasoning in forming our belief in continued existence. Once that influence is understood, Hume's theory ofcausation can itselfbe seen in a new light. Early in the Treatise, it does not seem as ifthere will be a problem in explaining beliefin the continuing existence ofindependent, thatis, unperceived, bodies. We readily suppose an object may continue individually the same, tho' severaltimesabsentfrom andpresenttothe senses; andascribe to itOn identity, notwithstanding the interruption of the perception, whenever we conclude, that if we had kept our eye or hand constantly upon it, it wou'd have convey^ an invariable and uninterrupted perception. But this conclusion beyond the impressions ofour senses can be founded only on the connexion ofcause and effect; nor can we otherwise have any security, that the object is not chang"d upon us, however much the new object may resemble that which was formerly present to the senses. Whenever we discover such a perfect resemblance, we consider, whether it be common in that species of objects; whether possibly or probably any cause cou'd operate in producing the change and resemblance; and according as we determine concerning these causes and effects, we form our judgment concerning the identity of the object. Volume XVIII Number 2 209 ALAN HAUSMAN AND DAVID HAUSMAN Here then it appears, that ofthose three relations, which depend not upon the mere ideas, the only one, that can be trac'd beyond our senses, and informs us of existences and objects, which we do not see or feel, is causation. (T 74) What is Hume committing himself to here? It certainly seems to be that,ifthereiscausal reasoninggoingonviathe principle ofassociation ofcausation in the cases he cites, itis done upon the observation ofthe constant conjunctions of physical objects and events. Furthermore, if we considercausation as aphilosophical relation, wehave here genuine constant conjunctions which would justify the belief that physical objects exist unperceived.3 Granted that sometimes we associate causally on the basis of*bad' constant conjunctions, there is no prima facie reason to think that this case is one of them. Given these implications, the knowledgeable reader of Hume must be taken somewhat aback; this does not sound like the arch sceptic of all time talking. Yet there are no qualifying passages around the onejust cited. Hume now embarks on his long analysis ofthe causal relation. He then turns, in the section "Ofscepticism with regard to the senses," to a detailed explanation of our belief in the continuing existence of unperceived bodies. He uses as one illustration a fire that one observes, after leaving one's chamber then returning, to have changed in the interim. Since we are accustomed in other instances to seeing the fire burn down, we here reason from what he calls the coherence of the change to the beliefthat the fire existed when we were not in the room. We have in the past observed five log fires burn down to four log fires and then to three log fires. We light a five log fire, leave the room, and return to a three log fire. Using coherence as our guide, we reason that there was a four log fire in the interim. What sort of reasoning...