there is nonetheless such an idea. That there is an objective physical necessity to which this idea corresponds is an untestable hypothesis, nor would demonstrating that such necessary connections had held in the past guarantee that they will hold in the future. Thus, while not denying that there may be physical necessity or that there is an idea of necessary connection, Hume remains a skeptic about causal necessity. Hume’s account of our belief in future effects or absent causes – of the process of mind that enables us to plan effectively – is a part of this same explanation. Such belief involves an idea or conception of the entity believed in, but is clearly different from mere conception without belief. This difference cannot be explained by supposing that some further idea, an idea of belief itself, is present when we believe, but absent when we merely conceive. There is no such idea. Moreover, given the mind’s ability to freely join together any two consistent ideas, if such an idea were available we by an act of will could, contrary to experience, combine the idea of belief with any other idea, and by so doing cause ourselves to believe anything. Consequently, Hume concludes that belief can only be a ‘different MANNER of conceiving an object’; it is a livelier, firmer, more vivid and intense conception. Belief in certain ‘matters of fact’ – the belief that because some event or object is now being experienced, some other event or object not yet available to experience will in the future be experienced – is brought about by previous experience of the constant conjunction of two impressions. These two impressions have been associated together in such a way that the experience of one of them automatically gives rise to an idea of the other, and has the effect of transferring the force or liveliness of the impression to the associated idea, thereby causing this idea to be believed or to take on the lively character of an impression.
Our beliefs in continuing and independently existing objects and in our own continuing selves are, on Hume’s account, beliefs in ‘fictions,’ or in entities entirely beyond all experience. We have impressions that we naturally but mistakenly suppose to be continuing, external objects, but analysis quickly reveals that these impressions are by their very nature fleeting and observer-dependent. Moreover, none of our impressions provides us with a distinctive mark or evidence of an external origin. Similarly, when we focus on our own minds, we experience only a sequence of impressions and ideas, and never encounter the mind or self in which these perceptions are supposed to inhere. To ourselves we appear to be merely ‘a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement.’ How do we, then, come to believe in external objects or our own selves and self-identity? Neither reason nor the senses, working with impressions and ideas, provide anything like compelling proof of the existence of continuing, external objects, or of a continuing, unified self. Indeed, these two faculties cannot so much as account for our belief in objects or selves. If we had only reason and the senses, the faculties championed by, respectively, the rationalists and empiricists, we would be mired in a debilitating and destructive uncertainty. So unfortunate an outcome is avoided only by the operation of an apparently unreliable third faculty, the imagination. It, by means of what appear to be a series of outright mistakes and trivial suggestions, leads us to believe in our own selves and in independently existing objects. The skepticism of the philosophers is in this way both confirmed (we can provide no arguments, e.g., proving the existence of the external world) and shown to be of little practical import. An irrational faculty, the imagination, saves us from the excesses of philosophy: ‘Philosophy wou’d render us entirely Pyrrhonian,’ says Hume, were not nature, in the form of the imagination, too strong for it. Books II and III of the Treatise and the Enquiry concerning the Principles of Morals reveal Hume’s concern to explain our moral behavior and judgments in a manner that is consistent with his science of human nature, but which nonetheless recognizes the irreducible moral content of these judgments. Thus he attempted to rescue the passions from the ad hoc explanations and negative assessments of his predecessors. From the time of Plato and the Stoics the passions had often been characterized as irrational and unnatural animal elements that, given their head, would undermine humankind’s true, rational nature. Hume’s most famous remark on the subject of the passions, ‘Reason is, and ought only to be, the slave of the passions,’ will be better understood if read in this context (and if it is remembered that he also claims that reason can and does extinguish some passions). In contrast to the long-standing orthodoxy, Hume assumes that the passions constitute an integral and legitimate part of human nature, a part that can be explained without recourse to physical or metaphysical speculation. The passions can be treated as of a piece with other perceptions: they are secondary impressions (‘impressions of reflection’) that derive from prior impressions and ideas. Some passions (pride and humility, love and hatred) may be characterized as indirect; i.e., they arise as the result of a double relation of impressions and ideas that gives them one form of intentional character. These passions have both assignable causes (typically, the qualities of some person or some object belonging to a person) and a kind of indirect object (the person with the qualities or objects just mentioned); the object of pride or humility is always oneself, while the object of love or hatred is always another. The direct passions (desire, aversion, hope, fear, etc.) are feelings caused immediately by pleasure or pain, or the prospect thereof, and take entities or events as their intentional objects. In his account of the will Hume claims that while all human actions are caused, they are nonetheless free. He argues that our ascriptions of causal connection have all the same foundation, namely, the observation of a ‘uniform and regular conjunction’ of one object with another. Given that in the course of human affairs we observe ‘the same uniformity and regular operation of natural principles’ found in the physical world, and that this uniformity results in an expectation of exactly the sort produced by physical regularities, it follows that there is no ‘negation of necessity and causes,’ or no liberty of indifference. The will, that ‘internal impression we feel and are conscious of when we knowingly give rise to’ any action or thought, is an effect always linked (by constant conjunction and the resulting feeling of expectation) to some prior cause. But, insofar as our actions are not forcibly constrained or hindered, we do remain free in another sense: we retain a liberty of spontaneity. Moreover, only freedom in this latter sense is consistent with morality. A liberty of indifference, the possibility of uncaused actions, would undercut moral assessment, for such assessments presuppose that actions are causally linked to motives.
Morality is for Hume an entirely human affair founded on human nature and the circumstances of human life (one form of naturalism). We as a species possess several notable dispositions that, over time, have given rise to morality. These include a disposition to form bonded family groups, a disposition (sympathy) to communicate and thus share feelings, a disposition – the moral sense – to feel approbation and disapprobation in response to the actions of others, and a disposition to form general rules. Our disposition to form family groups results in small social units in which a natural generosity operates. The fact that such generosity is possible shows that the egoists are mistaken, and provides a foundation for the distinction between virtue and vice. The fact that the moral sense responds differently to distinctive motivations – we feel approbation in response to well-intended actions, disapprobation in response to ill-intended ones – means that our moral assessments have an affective but nonetheless cognitive foundation. To claim that Nero was vicious is to make a judgment about Nero’s motives or character in consequence of an observation of him that has caused an impartial observer to feel a unique sentiment of disapprobation. That our moral judgments have this affective foundation accounts for the practical and motivational character of morality. Reason is ‘perfectly inert,’ and hence our practical, actionguiding moral distinctions must derive from the sentiments or feelings provided by our moral sense.
Hume distinguishes, however, between the ‘natural virtues’ (generosity, benevolence, e.g.) and the ‘artificial virtues’ (justice, allegiance, e.g.). These differ in that the former not only produce good on each occasion of their practice, but are also on every occasion approved. In contrast, any particular instantiation of justice may be ‘contrary to the public good’ and be approved only insofar as it is entailed by ‘a general scheme or system of action, which is advantageous.’ The artificial virtues differ also in being the result of contrivance arising from ‘the circumstances and necessities of life.’ In our original condition we did not need the artificial virtues because our natural dispositions and responses were adequate to maintain the order of small, kinshipbased units. But as human numbers increased, so too did the scarcity of some material goods lead to an increase in the possibility of conflict, particularly over property, between these units. As a consequence, and out of self-interest, our ancestors were gradually led to establish conventions governing property and its exchange. In the early stages