Filling the Gaps: Hume and Connectionism on the Continued Existence of Unperceived Objects

Hume Studies Volume XXV, Numbers 1 and 2 , April/November 1999, pp. 155-170 Filling the Gaps: Hume and Connectionism on the Continued Existence of Unperceived Objects MARK COLLIER In Book I, part iv, section 2 of the Treatise, "Of scepticism with regard to the senses," Hume presents two different answers to the question of how we come to believe in the continued existence of unperceived objects.1 He rejects his first answer shortly after its formulation, and the remainder of the section articulates an alternative account of the development of the belief. The account that Hume adopts, however, is susceptible to a number of insurmountable objections, which motivates a reassessment of his original proposal . This paper defends a version of Hume's initial explanation of the belief in continued existence and examines some of its philosophical implications. The question of how we acquire the belief in continued existence poses a hard problem for Hume, since he is committed to two theses which severely constrain the answers he can give. The first thesis, indeed the first principle of Hume's science of human nature, is that all of our ideas are derived from impressions (T 7).2 The second is that the sequences of impressions that constitute our acquaintance with objects are "gappy"; one need only turn one's gaze away from an object, or simply blink, to cause the train of perceptions to become fragmentary and interrupted.3 The conjunction of these two theses threatens to render an empiricist explanation of continued existence intractable. On the one hand, the idea of continued existence must arise from the senses, yet on the other, the senses do not directly deliver this information. Mark Collier is a Fellow in the Humanities at Stanford University, Department of Philosophy, Building 90, Stanford, CA 94305, USA. e-mail: mcollier@stanford.edu 156 Mark Collier Because the senses can play no more than a partial explanatory role, Hume must recruit the help of an additional faculty to supplement the information they deliver. The faculty to which he turns, as he does so often in the Treatise, is the faculty of the imagination. Hume's "hypothesis" is that the belief in continued existence emerges from the interaction of the senses and the imagination , or in his own words, the "concurrence of some [sensory] qualities with the qualities of the imagination" (T 194). Hume's general explanatory strategy in Treatise I iv 2, then, is threefold. First, he will isolate the sensory qualities that are involved in attributions of continued existence. Second, he will provide an account of the principles of the imagination that accompany instances of the belief. Finally, he will explain how the principles of the imagination interact with the sensory qualities to produce the belief in continued existence . In fact, Hume presents two formulations of this hypothesis. Let us reverse the order of Hume's exposition and begin with the second formulation. As dictated by his explanatory strategy, Hume must first choose the sensory qualities to play the partial explanatory role. Amid the changing contents of consciousness , he tells us, certain series of impressions exhibit the property of "constancy." A series of impressions is constant if it is interrupted, yet recommences without any qualitative alteration. Adopting Barry Stroud's formalism, we may express a paradigmatic constant series the following way, with letters representing impressions, and squares representing observational gaps:4 AAAAAAD D DAAAAAA The resemblance of the impressions on each side of the gap is an important feature of constant series, since the resulting association leads the imagination to pass over the interruption in the sequence and conflate the broken series with one that is complete.5 Subsequent reflection upon the appearance of such series, however, reveals their undeniable diversity. The result is a conflict of principles, which the imagination can only resolve through the supposition that the object continued to exist, although unperceived (T 199). Unfortunately, there are a number of reasons why this explanation, which we might call the "conflation" account, has neither the virtues of plausibility nor consistency. First, the exclusive appeal to constancy represents a significant confusion on Hume's part. Constancy cannot be the sole sensory quality accompanying all of...