Hume's Determinism

David Hume has traditionally been assumed to be a soft determinist or compatibilist,¹ at least in the 'reconciling project' that he presents in Section 8 of the first Enquiry, entitled 'Of liberty and necessity.'² Indeed, in encyclopedias and textbooks of Philosophy he is standardly taken to be one of the paradigm compatibilists, rivalled in significance only by Hobbes within the tradition passed down through Locke, Mill, Schlick and Ayer to recent writers such as Dennett and Frankfurt.³ Many Hume scholars also concur in viewing him as a determinist, for example (in date order) Norman Kemp Smith, Barry Stroud, A. J. Ayer, Paul Russell, Don Garrett, Terence Penelhum, George Botterill, John Bricke, and John Wright.⁴ My main purpose in this paper will be to provide the evidence to substantiate this traditional interpretation, which has hitherto been widely assumed rather than defended. In the absence of such a defence, the consensus has been left open to challenge, most notably in a recent paper and a subsequent book by James Harris, who boldly claims that Hume 'does not subscribe to determinism of any kind, whether Hobbesian or merely nomological.'⁵ His main arguments for this claim are drawn from his analysis of Hume's treatment of the idea of necessity and its deployment in support of the 'Doctrine of Necessity.' But Harris also alludes to — and apparently puts significant weight on — a supposed tension between determinism and Hume's famous 'sceptical' views about induction and causation. Since this latter issue raises fundamental questions regarding the interpretation of Humean determinism, it will be helpful to deal with it first, before turning to Harris's more extensive arguments concerning Hume's discussions of liberty and necessity.

I Determinism and Humean 'Scepticism'

Harris does not fully spell out why he considers Hume's famous argument concerning induction, and his equally famous discussion of causation, to be incompatible with a determinist perspective, though the following passage (from Harris 2003, 464-5) makes reasonably clear why he sees some tension between the two:

Hume begins his examination of the doctrine of necessity by describing what is 'universally allowed' as regards material bodies ... :

It is universally allowed, that matter in all its operations, is actuated by a necessary force, and that every natural effect is so precisely determined by the energy of its cause, that no other effect, in such particular circumstances, could possibly have resulted from it. ...

(E 8.4)

... there is no reason to think Hume here forgets all that he has previously established concerning our inability to prove the laws of nature to be immutable. Hume is merely reporting, and not endorsing, what is universally allowed. And in point of fact, there is no empirical basis for the belief that nothing in nature could be otherwise than it is. 'Our idea ... of necessity and causation,' Hume points out, 'arises entirely from [observed uniformity and customary inference]. These two circumstances form the whole of that necessity, which we ascribe to matter. Beyond the constant conjunction of similar objects, and the constant inference from one to the other, we have no notion of any necessity, or connexion.' (E 8.5) What is universally allowed thus outstrips somewhat its evidential base, and is presumably derived in some way from what Hume in the Treatise describes as the mind's 'great propensity to spread itself on external objects ...'

There are two main thoughts here. First, Hume's argument concerning induction has shown that we are unable 'to prove the laws of nature to be immutable.'⁶ Second, our understanding of necessity and causation is derived purely from observed uniformity and a consequent tendency to infer from 'cause' to 'effect': this is clearly inadequate as an evidential base from which to infer anything as strong as universal determinism.

Now is not the time to debate the interpretation of Hume on induction and causation,⁷ so I shall confine myself here to some general comments that are, I hope, relatively uncontroversial. The famous argument concerning induction aims to show that the presupposition of such inference — namely 'that the future will resemble the past' (E 4.21...