One of the sciences comprised in Hume’s Science of Human Nature is metaphysics, understood as the science of the most general features of the world as it appears to us. I show how Hume’s metaphysics in the Treatise can be “methodized, or reduced to general principles.” Those principles are: (I) The Contradiction Principle: The distinctly conceivable implies no contradiction. (II) The Possibility Principle: What implies no contradiction is possible. (III) The Conceptual Separability Principle: Things are different if and only if separable in conception. On these principles the rest of Hume’s metaphysics is based, including his atomistic ontology and his denial of necessary connection: only single, individual, simple, unaltering, determinate, particular, metaphysically independent things exist.

Hume argues that there cannot be any act of the mind by means of which we create a moral obligation at will. I argue that nonetheless, on Hume’s view, to promise is, fundamentally, to obligate myself intentionally by my utterance (though not merely by an act of mind). The convention of promises, as he constructs it, gives an individual the power to change the sentiments of the community (regarding a certain action) by speaking. Given his account of obligation, that change makes the described action obligatory. This explains why Hume initially found promises mysterious and how the convention removes the mystery. It also reveals a sharp difference between Hume’s explanation of promissory obligation and that found in present-day assurance theories, according to which the obligation cannot be created merely by an intentional act of self-obligation but depends crucially on the mental states of the promisor and the promise’s recipient.

Today, the Treatise is Hume’s most well-known work. But that was not so in the eighteenth century. Hume could even famously claim that his Treatise “fell dead-born from the press.” Still, modern scholarship has shown that the Treatise had a more significant early reception than Hume’s comment suggests. This chapter sheds new light on the reception of Hume’s Treatise in eighteenth-century Britian. It surveys the existing historiography and considers Hume’s relevant surviving correspondence. But it also explores overlooked dimensions of the Treatise’s early reception, partly by employing data mining in electronic databases, particularly Eighteenth Century Collections Online (ECCO). Analyzing that data in various ways, we illuminate new dimensions of this topic. They include unpacking close engagements by familiar figures, like Lord Kames; casting light on the many who invoked, critiqued, anthologized, or otherwise absorbed and broadcast the Treatise; and identifying the larger trends of eighteenth-century reuse to which all of those individual stories contributed.

Hume clearly distinguishes between better and worse causal inferences, notably in his “Rules by which to judge of causes and effects” in Treatise 1.3.15. Although Hume describes these rules as “all the logic I think proper to employ” in his philosophy (Treatise 1.3.15.11), the literature has paid relatively little attention to it. This chapter will investigate these eight rules, as well as their basis in Hume’s discussion of general rules. The paper then examines two controversial causal inferences in light of these rules by which to judge of causes and effects: first, the postulation of the calm passions; second, the missing shade of blue. As Hume himself recognizes, the correct application of these rules can be an enigmatic affair. Nevertheless, I find that there is reason to think that while Hume abides by these rules in his postulation of the calm passions, the missing shade of blue constitutes a gross violation of these same rules.

The introduction to this Critical Guide offers some background to Hume’s classic A Treatise of Human Nature, originally published in three books in 1739 and 1740. The introduction then briefly broaches the debate whether Hume leaves the doctrines of the Treatise behind with his later works, and it defends the importance of the Treatise to Hume’s corpus and to subsequent and contemporary philosophical thought. It presents a summary of the fourteen critical essays contained in the volume, which include seven articles on Hume’s epistemology and philosophy of mind, six articles on the passions and ethics, and one essay on the early reception of the Treatise. Several of these essays highlight the unity of Hume’s approach in the Treatise, showing how the principles of Hume’s epistemology and psychology in Book 1 are foundational to his discussion of the passions and of morality in Books 2 and 3.

Hume writes that it is “no inconsiderable part of science barely to know the different operations of the mind, to separate them from each other, to class them under their proper heads, and to correct all that seeming disorder, in which they lie involved, when made the object of reflection and enquiry.” He describes this branch of knowledge as “mental geography.” Yet while his mental geography of thought is now well understood, his mental geography of feeling—specifically, of the non-sensory “secondary impressions” or “impressions of reflection” that he discusses in Books 2 and 3 of A Treatise of Human Nature—has not been. This essay seeks to clarify Hume’s doctrines in these two Books by explaining the nature and classification of the five kinds of secondary impressions that Hume distinguishes: (1) sensible agitations (i.e., “emotions” in one sense of that term); (2) feelings of or from mental operations; (3) volitions; (4) passions (both calm and violent); and (5) sentiments of taste.

This chapter addresses three questions that arise from Hume’s observations about character in the Treatise: whether Hume can talk about enduring traits that constitute character, given his depiction of the mind as in flux; whether character is “objective” or a creation of spectators; and whether Hume’s treatment of virtue and vice is only descriptive of how we derive our moral categories. I argue, first, that since Hume distinguishes between the feeling of a motive and its causal efficacy, he can observe that, while feelings may be fluid, character is determined by which has the force to produce action consistently. Second, the contingency of moral categories on human nature is not the same as creation of the features that fall under those categories. Third, Hume both describes our process of moral discrimination and offers guidance about making judgments of virtue and vice. However, he is not defending his view of moral character but employing the norms that arise from human practices.

In this chapter, I argue for the centrality of Hume’s detailed exposition of the association of ideas in fulfilling the goals which he sets out in the Introduction to the Treatise—namely that of providing a foundation for the other sciences including the science of human nature, and applying the experimental method in its foundation. I discuss three different physical models of association of ideas which Hume presents and their appropriateness to the way he applies his theory to explain phenomena. I begin by putting Hume’s account of the association of ideas in its historical background, and conclude with comments on how it was taken up by his eighteenth-century Scottish successors. Hume’s positive account is contrasted with the negative account found in his predecessors Locke and Hutcheson, and his limited principles of association are contrasted with the more extensive principles found in the writings of Kames, Gerard, Reid and Dugald Stewart.

For many readers, Hume’s lengthy analysis of the passions in Book 2 has questionable philosophical returns compared to the rest of the Treatise. This paper provides a guide to a philosophically rich reading of Book 2. Instead of a disconnected series of individual arguments, Book 2 is the second half of Hume’s theory of human cognition as started in Book 1. Guided by a comparison with Hume’s A Dissertation on the Passions, I argue that Hume is not merely applying Book 1 principles to the passions, but introducing new principles governing how feeling attends to and transfers between our perceptions. Employing his methodology of experimental reasoning, Hume identifies differences between ideas and impressions, and explores how their interactions impact the movement and quality of affectivity. This is a significant expansion on the associationism of Book 1 of the Treatise, providing more sophisticated explanations and predictions concerning mental life.

This chapter demonstrates that a correct understanding of Kant’s argument for the bindingness of the moral law in Groundwork III succeeds. Through his critique of the conditions of the possibility of the act of willing, Kant demonstrates that any act of the will involves our activity as intelligences. This includes action in accordance with hypothetical imperatives, which involves the capacity to understand what is required in order for us to influence the world and so act in it; it requires the capacity to act in accordance with laws. Kant characterizes his argument in Groundwork III as a deduction answering the question: With what right we are bound by the categorical imperative? It proceeds in three essential steps: an analysis of (1) negative freedom and the logical conditions of judgment in all practical principles; (2) moral valuation and the problem of the circle, and (3) positive freedom as implied in the act of reflection as the self understands itself as acting in accordance with the idea of laws. When we so act, we transfer ourselves into the world of intelligences and must assume the conditions of membership in such a world. These include being bound by the moral law.

Hume criticized the idea that all legitimate government rests on consent of any sort, tacit or express. He did not deny that some governments originated that way, or that it was an admirable way. But he thought it absurd to claim that legitimate government authority is contingent upon each subject’s consent. To say that it is so is contrary to common opinion and, moreover, simply shifts the question to that of the bindingness of promises. That bindingness must rest on the idea of necessity, and so it is needlessly indirect to appeal to promises when government can be justified directly by its necessity to prosperous and secure society. Hume, however, also made a positive contribution to the social contract tradition. He described how a convention, or common practice, can coordinate expectations and behavior without the need for any express agreement or contract. Later theorists make use of Humean convention in order to connect the idea of hypothetical consent to the actual circumstances of life. In short, government is legitimate where there is a convention of conformance to a social contract that would, hypothetically, be approved by clear-minded individuals.

Hume’s and Bentham’s criticisms of natural law theory are direct and even mocking. By contrast, Kant’s approach in the Feyerabend lectures is far more restrained. Having adopted for his course an author explicitly committed to natural law premises, Kant largely avoids open conflict with those premises, choosing instead to develop his claims about right without making any direct critique (or defense) of the appeal to natural law. What accounts for this difference? After briefly reviewing the history of natural law theory in the modern period, I turn to a close reading of Kant’s brief but pointed criticisms of Achenwall in the opening sections of the Feyerabend lectures. I argue that Kant understands a theory of natural law not as opposed to but as irrelevant to a theory of right. Once we appreciate this claim, we can better understand Kant’s equally important contribution to the decline of natural law theory in the tradition of liberal political theory.

This final chapter turns to the other basic question that MacCormick asked himself, again exploring it for over four decades: is reason practical, and if so how? MacCormick engaged in this question in the form of a life-long dialogue with his Enlightenment predecessors, and especially Stair, Hume, Smith, and Kant. This chapter tracks this dialogue, while also keeping in mind the contemporary interlocutors of MacCormick’s theory of practical reason, which included not only the dominant voices in Anglo–American jurisprudence, such as Hart and Dworkin, but also philosophers in the European Continent, such as Perelman and Alexy. The first part of the chapter focuses on what may be called MacCormick’s meta-ethics, showing how MacCormick adopted perspectivalism about value. The second shows how, particularly in his theory of legal reasoning, MacCormick discusses the importance of constructing an inter-subjective space (via universalisation) and how he explores the complexity of deliberation as well as the defeasibility of decision within that space. Throughout, the chapter reads MacCormick’s account of the limited practicality of reason as a matter of character.

Shelley was an adherent to the basic tenet of empiricism, that ‘the senses are the only inlets of knowledge’. Yet he also affirmed that there are things we only ‘feel’ to be true. Rooted in Hume’s distinction between ‘impressions’ and ‘ideas’ – between sensory perceptions and the pictures in our minds, distinguishable only by the relative strength of their appearances – Shelley developed the notion of an ‘inward sense’ that guides us in our feelings or intuitions and discerns between real and ideal things. Above and beyond the philosophy of the British empiricists and the scepticism of Hume, yet rooted in their works, Shelley also developed in his verse a notion of what it would mean for an ‘idea’ to outstrip an ‘impression’ – for the world of the imagination to surpass the real thing, and for poetry to offer up ideas of greater force than empirical reality.

Chapter 3 shifts to the period in which the constitutional debates following the revolution of 1688 gave way to a long period of greater political stability. The Tories were ousted with the coming of the Hanoverian dynasty in 1714, after which the Whigs settled into power under the leadership of Robert Walpole. The chapter first shows how the Whig oligarchy was opposed by a new generation of ‘commonwealthmen’, notably Trenchard and Gordon, and by a more conservative opposition led by Bolingbroke, who appropriated many ‘commonwealth’ themes. Next the chapter surveys the success of the Whigs in countering these opponents and cementing themselves in power. After their triumph over the Jacobite rebellion in 1745 the Whigs presided over an outpouring of patriotic sentiment. They were congratulated for repudiating arbitrary power, granting the people a voice in making the laws and guaranteeing their basic rights, and thereby ensuring that Britian was genuinely a free state.