Inductive Scepticism and Experimental Reasoning in Moral Subjects in Hume's Philosophy

Inductive Scepticism and Experimental Reasoning in Moral Subjects in Hume's Philosophy Anne Jaap Jacobson According to its title page, Hume's Treatise Concerning HumanNature is An ATTEMPT to introduce the experimental Method ofReasoning INTO MORAL SUBJECTS."1 And from the first section onwards, Hume makes statements about the human mind which are given an unqualified generality;An Enquiry ConcerningHuman Understanding is marked by a similar assurance that much about human understanding can be known. Because of this, exegesis which attributes to Hume an unrestrained scepticism about the experimental method appears to attribute to him inconsistency on such a scale as to render the interpretation itselfquestionable. Nonetheless, there is, atleast on the face ofit, considerable justification for ascribing to Hume just such a scepticism. In this paper I explore sceptical features, some ofthem important but little noticed, in Hume's treatment of causality and our beliefs about the unobserved. Though I end by suggestinghow to avoidviewing Hume in this area as simply lamentably inconsistent, Hume's use of the experimental method doesremain problematic, as, I suggest, Hume himselfthought. The first three of the following sections in this paper treat connected themes in Hume's philosophy which, when taken together, present us with a very sceptical view of experimental reasoning. I. Necessity as projected impression Hume holds that our beliefs about causality in the objects are in large part the result of a projection of an internal impression of (some kind of) necessity. The thesis ofprojection is not entirely straightforward; to see this, let us ask the question, is the impression which is projected semantically simple or complex? There are excellentreasonsforregarding the impression as simple as Hume conceives of "simple" in this context. Hume himselfappears to sayitis simple (E 64, n. 1). Andmuch of Hume's discussion ofnecessity is driven by the principle that there can be no idea without a preceding impression, and this principle applies only to simple ideas. But the consequent reading is far from satisfactory. To see the problem, let us look at what seems to be the Volume XV Number 2 325 ANNE JAAP JACOBSON most entrenched understanding ofHume, one perhaps amark ofKemp Smith's influence. This is the view that Hume is saying that the impression source of our idea of necessity is a feeling of anticipation. The problem is this: ifa feeling ofanticipation is a simple impression, it is not at all clear that the impression can do the job Hume has for it. Remember that if the impression is in content itselfrelational, then it is not a simple impression on Hume's own account, since ideas of relations are for him complex (T 13). Hence, we might take the impression to be of the sort described by Stroud, according to whom the impression yielding our idea of necessity is semantically unrelated to the elements of the relation. But such a reading robs Hume of the explanatory position he so clearly thinks he has. If we have a semantically simple impression it becomes a mystery why the spreading has the effects that it does: when we transfer the determination ofthe thought to external objects, andsuppose any real intelligible connexion betwixt them. (T 168, my emphasis) Why does spreading some simple, indefinable feeling result in our supposing there is a real intelligible connection between the objects on which the mind has spread? To get this result it looks as though the mind will have tomake two mistakes: thefirstmistake is the spreading, and the second mistake consists in the mind's inferring from the experience of the impression as spread that somehow the causal inference itself is also out there in nature as an intelligible connection. But, while Hume does sometimes seem to suggest we make this sort of two-step error (T 223, for example), such a picture makes it seem that the impression spread is not really the semantic source of (that is, wholly determinate of the content of) our idea ofnecessity. Rather, on the two-step error model, our belief that there are connections enters as a result of an inference following upon the spreading; however, for Hume, an inference is not the way an impression ofX gives rise to an idea ofX...