I'm continuing my series on libertarianism (in the free will sense); by my rough estimate I should have at least seven or eight posts total by the time I'm done. (Don't worry; they aren't all as indirect as these first two.) This one should be taken in conjunction with Point # 1.
Point #2: If event-based analyses of causation drive us inevitably to something like Hume's position on causation, they drive us inevitably to something like Hume's position on liberty and necessity.
I suggested the antecedent in Point #1. Here I will suggest 1) my reason for thinking the conditional is true; and 2) more importantly, I will point out what I would have thought rather obvious, but which no one else seems to allow, namely, that Hume's position on free will causes as much trouble for determinists as it does for libertarians.
2.1 Hume's position on liberty and necessity, as presented in the Treatise and the Enquiry, follows fairly easily from his views on causation. In Hume's theory of causation, causation, objectively, is nothing but constant conjunction; subjectively, it is constant conjunction plus a determination of the mind to infer one element in the conjunction from another. Hume's account of liberty and necessity is simply an attempt to apply the theory of causation seriously to this issue. The heart of Hume's causal theory is causal inference; as he notes in Part 3 of Book I of the Treatise, it consists in taking causation to be based on the inference rather than vice versa. So, given that we do make such causal inferences in human actions, and given some other aspects of Hume's analysis that follow from the basic core of the theory as corollaries, it's clear that necessity in Hume's sense applies to human actions, and the word 'liberty' has to be used in such a way that it is consistent with this sense of 'necessity'.
2.2 What always puzzles me, though, is that compatibilists and determinists think Hume is on their side. In fact, Hume is often called a compatibilist. If by 'compatibilist' you mean anyone who thinks that 'necessity' understood in a certain way can be applied to the same things 'liberty' understood in a certain way can be applied to, then Hume is a compatibilist. But compatibilism in this sense is pretty much a useless label; anyone can redefine the terms as they will. And it is simply a matter of labels. Hume uses the word 'necessity' simply because that's his word for inferential connection. In actuality, Hume's position is quite inconsistent with any determinism that could be proposed, because determinism is largely a non-issue in Hume's causal theory. The only relevant aspect of causation in Hume's theory is inferability. That we can infer C from E or E from C is all that Hume intends in talking about the 'necessity' of actions. And it is important to note that this inference is not an implication - i.e., it is not a logical inference. When Hume says there's a necessary connection between C and E, he simply means that we develop a very strong habit of concluding that if there's a C there's an E, and vice versa. (There's a slight complication given that Hume also has an account of how these habits are shaped by progressively more consistent maxims, but this doesn't change the essentials.) Unless by 'determinism' you just mean that we can draw conclusions about human actions, Hume's theory weakens causation far too much to be deterministic. Indeed, Hume's theory requires that there is no objective determinism at all; no system, in itself, is deterministic on Hume's analysis. 'Necessity' is a habit of association, and nothing more. So Hume's determinism causes quite as much trouble for almost anything that could plausibly be called 'determinism' as it could possibly for libertarian views.
And Hume himself explicitly recognizes this, because he insists that he is not changing our notions of liberty, but our notions of necessity, by insisting that there is no necessity except what used to be called 'moral necessity'. He notes:
I define necessity two ways, conformable to the two definitions of cause, of which it makes an essential part. I place it either in the constant union and conjunction of like objects, or in the inference of the mind from the one to the other. Now necessity, in both these senses, has universally, tho' tacitely, in the schools, in the pulpit, and in common life, been allow'd to belong to the will of man, and no one has ever pretended to deny, that we can draw inferences concerning human actions, and that those inferences are founded on the experienc'd union of like actions with like motives and circumstances. The only particular in which any one can differ from me, is either, that perhaps he will refuse to call this necessity. But as long as the meaning is understood, I hope the word can do no harm. Or that he will maintain there is something else in the operations of matter. Now whether it be so or not is of no consequence to religion, whatever it may be to natural philosophy. I may be mistaken in asserting, that we have no idea of any other connexion in the actions of body, and shall be glad to be farther instructed on that head: But sure I am, I ascribe nothing to the actions of the mind, but what must readily be allow'd of. Let no one, therefore, put an invidious construction on my words, by saying simply, that I assert the necessity of human actions, and place them on the same footing with the operations of senseless matter. I do not ascribe to the will that unintelligible necessity, which is suppos'd to lie in matter. But I ascribe to matter, that intelligible quality, call it necessity or not, which the most rigorous orthodoxy does or must allow to belong to the will. I change, therefore, nothing in the receiv'd systems, with regard to the will, but only with regard to material objects. (Treatise 2.2.1 Part II)
And from this, I think, it could be argued that Hume's so-called 'compatibilism' is more of a problem for determinism than libertarianism: if you can have a libertarianism that allows for moral evidence and inference, you are unaffected by Hume's basic arguments; no determinist can be unaffected by them. But I will not argue this here. Suffice it to say that determinists who consider Hume on their side will find him a false friend, since Humean analysis implies that there is no objective determinism, and makes necessity into nothing but customary inferability. But if I am right that event-based analysis of causation forces us to a Humean theory of causation, and that Hume's position on liberty and necessity is simply an application of this, then this is the position to which most determinists in analytic philosophy today would be committed, were they consistent.