  Hume is traditionally regarded as a compatibilist about freedom and determinism, because in his discussion in the Enquiry concerning Human Understanding he argues that if we understand the doctrines of liberty and necessity properly, all mankind consistently believe both that human actions are the products of causal necessity and that they are free. In the Treatise, however, he explicitly repudiates the doctrine of liberty as “absurd... in one sense, and unintelligible in any other” (T 2.3.2.1). The two treatments, however, surprisingly enough, are entirely consistent. Hume construes causal necessity to mean the same as causal connection (or rather, intelligible causal connection), as he himself analyzes this notion in his own theory of causation: either the “constant union and conjunction of like objects,” or that together with “the inference of the mind from the one to the other” (ibid.). In both works he argues that just as we discover necessity (in this sense) to hold between the movements of material bodies, we discover just as much necessity to hold between human motives, character traits, and circumstances of action, on the one hand, and human behavior on the other. He says in the Treatise that the liberty of indifference is the negation of necessity in this sense; this is the notion of liberty that he there labels absurd, and identifies with chance or randomness (which can be no real power in nature) both in the Treatise and the first (epistemological) Enquiry. Human actions are not free in this sense. However, Hume allows in the Treatise that they are sometimes free in the sense of ‘liberty’ which is opposed to violence or constraint. This is the sense on which Hume focuses in EcHU: “a power of acting or not acting, according to the determinations of the will;” which everyone has “who is not a prisoner and in chains” (EcHU 8.1.23, Hume’s emphasis). It is this that is entirely compatible with necessity in Hume’s sense. So the positions in the two works are the same, although the polemical emphasis is so different — iconoclastic toward the libertarian view in the Treatise, and conciliatory toward “all mankind” in the first Enquiry.