Abstract

In lieu of an abstract, here is a brief excerpt of the content:Hume Studies Volume 30, Number 1, April 2004, pp. 33-50 Constancy, Coherence, and Causality IRA M. SCHNALL According to David Hume, we believe in the existence of an external world because of the phenomena of constancy and coherence (T 1.4.2.18-43; SBN 194-210).1 Hume delineated these two aspects of our sensory experience, and claimed that they influence the imagination in such a way as to generate belief in the existence of unperceived objects, independent of the mind. There is disagreement among philosophers as to the proper way to characterize constancy and coherence and the ways in which they respectively lead us to believe in external objects. The most straightforward account of coherence seems to make it the same as Hume's concept of causality. Yet Hume denies that they are the same ; and commentators disagree as to how to understand Hume's distinction between the two. As to constancy, many philosophers, following H.H. Price,2 have argued that it is really just a special case of coherence, and that its role in generating belief in external objects is the same as that of coherence. There is consequent puzzlement as to why Hume attributed a different, and more important, role to constancy. In an important recent book, Louis E. Loeb has proposed a very interesting two-part solution to this last puzzle: First, Hume is convinced that the commonsense view of the external world is patently false; so he cannot allow that it results from something as reasonable as causal inference. But the way coherence leads to belief in external objects is a form of causal inference. So, Hume wants constancy to lead to belief in external objects in a different, less reasonable way; and he wants constancy to be more important than coherence in leading to belief in the external world. Second, Hume did not realize that constancy is simply a special case of coherence (or causality), because of certain assumptions about causality that he Ira M. Schnall is at the Department of Philosophy, Bar-Ilan University, Ramat-Gan, Israel 52900. e-mail: [email protected] 34 Ira M. Schnall had inherited from his predecessors (i.e., he did not see the causality involved in the relation between an object's existing at one moment and its existing at a later moment). Therefore he appealed to non-rational mechanisms of the imagination to explain how constancy leads us to posit external objects.3 I will try to show that solutions such as Loeb's, which grant the affinity between coherence and causality and the reducibility of constancy to coherence, are unnecessary. I will propose a way to make sense of Hume's claim that coherence is not the same as causality; and I will argue that what Hume calls 'constancy' is not, and should not be, the same as, or reducible to, coherence. After introducing some basic terms, including 'constancy' and 'coherence' themselves (in section I), I will discuss the proper characterization of coherence and how it differs from causality (section II). Then I will discuss Hume's account of constancy and how it leads to belief in external obj ects; and I will contrast it with the alternative account, referred to above, that is widely held to be preferable (section III). I will argue that Hume's own account has certain advantages over the alternative (section IV) and that the main arguments against Hume's account are inconclusive (sections V and VI). The argument of section IV will yield an explanation of Hume's assigning more importance to constancy than to coherence. Finally, I will suggest (in the concluding section) that though Hume considered constancy and coherence to be merely the psychological "causes" that "induce us to believe in the existence of body," we can use them as a basis of an epistemological justification of our belief in the external world. I will make extensive use of H. H. Price's Hume's Theory of the External World; for much of the current understanding, as well as misunderstanding, of Hume's concepts of constancy and coherence is the result of the detailed analyses and arguments in that work.4 I First of...