Kant and the Stoics both rely on a momentous argument, set out in Plato’s dialogues, for the conclusion that nothing is unconditionally good but wisdom, yet they differ on how to interpret it. The Stoics identify this wisdom with the perfection of technical or productive knowledge of nature, and they regard it as the sole good. Kant identifies this wisdom with the perfection of practical knowledge of the good, and, analyzing this knowledge along the hylomorphic lines implicitly suggested in Plato’s argument, he locates wisdom’s unconditional goodness – its morality, or moral goodness – in its agreement not with the object it produces but with its form, morality’s principle. Two contrasting accounts of morality’s relation to perfection thus emerge. The Stoics see perfection in the knowledge of nature as entailing moral goodness, whereas Kant argues that moral goodness is the condition of all other goodness, including that of perfection.

This short epilogue concludes the book, with a brief reflection on MacCormick’s final book, Practical Reason in Law and Morality (2008), where MacCormick confronted his own impending death from cancer, and where he once again articulated a relational approach to ethics, politics, and law.

This chapter examines the intellectual, especially philosophical, context of MacCormick’s education as a philosopher, including his relationships with his teachers and their ideas. MacCormick’s own education is placed in a broader historical context, mainly by reference to the influential history published on it while MacCormick was studying: George Davie’s The Democratic Intellect (1961). While at the University of Glasgow, MacCormick was taught by a number of philosophers who had a considerable impact on his interests and orientations, including Robin Downie, David Raphael, and WD Lamont. This chapter discusses the work of these philosophers and considers how MacCormick related to them. There is a particular emphasis on Lamont and his concept of authority, as well as how he related law and morality.

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.

A rights-based theory of property relies heavily on practical reason. “Practical reason” is the domain in which people apply fundamental principles of moral reasoning to practice. This chapter contrasts practical reason with theoretical reason. It introduces specification (reasoning from broad moral rights to specific entitlements between right- and duty-holders), determination (the implementation of moral directives in law and other social conventions), and reasoning with core cases. This chapter’s argument dispels the “copy view” of morality, in which theories of morality must recommend in practice rules and institutions that follow closely from what they recommend in principle. This chapter also shows how practical reason considers the consequences of different proposed rights and policies, without becoming consequentialist or prioritizing social welfare over individual rights. This chapter shows how practical reason applies with speed limits and customary rights in snow-covered parking spaces.

The Cambridge Platonists’ philosophy of religion might be summed up as a tension between their commitment to the fixed nature of reason and goodness on the one hand and a commitment to freedom and distaste for all forms of tyranny and imposition on the other. This last chapter contends that the Cambridge Platonists not only acknowledge this tension, but embrace it, revelling in the paradoxical way that absolute fixedness and absolute freedom come together at the highest levels of being. This is made possible by what Stephen Darwall (writing specifically of Cudworth) has identified as an early theory of ‘practical reason’. This Platonic theory of practical reason draws together all the elements of the Cambridge Platonists’ outlook considered in earlier chapters – moral realism, divine communicative intent, and participatory epistemology, illustrating the extent to which this Platonic outlook binds together not only the thought of Whichcote, More, Cudworth and Smith but also runs through each of their views on different philosophical topics such as obligation, freedom and pedagogy.

Kant did not initially intend to write the Critique of Practical Reason, let alone three Critiques. It was primarily the reactions to the Critique of Pure Reason and the Groundwork of the Metaphysics of Morals that encouraged Kant to develop his moral philosophy in the second Critique. In this brief introduction I outline some of the major events that took place in Kant’s development between the first and second Critiques. I illustrate that the story of the Critique of Practical Reason’s origin reveals that it is especially suited to being accompanied by certain background source materials that help illuminate its aims and contents.

August Wilhelm Rehberg (1757–1836) was a civil servant in Hanover, but he also made several important contributions to the philosophical debates of his time. This chapter contains the first English translation of Rehberg’s review of the second Critique, which was highly influential and read by figures such as Reinhold and possibly Fichte as well. In the review, Rehberg doubts that pure reason can be practical. One of the most important statements of the review is Rehberg’s claim that the feeling of respect must be something sensible and, as such, must contain an element of pleasure, despite what Kant says. Kant was aware of the review and is thought to have responded to it in later works such as the third Critique.

Johann Georg Heinrich Feder (1740–1821) was a well-respected and well-known professor of philosophy at the University of Göttingen, especially during the 1770s and early 1780s. A turning point took place in Feder’s life and career, however, when he edited the infamous Göttingen review of the first Critique, which was originally written by Christian Garve and to which Kant responds in the Prolegomena. This chapter contains a complete translation of Feder’s review of the second Critique, which therefore captures the opinion of one of Kant’s most well-known and infamous critics. Feder discusses a number of topics in the review, including: whether pure reason can be practical without the assistance of feeling and inclination, the nature of good and evil and their relationship to pleasure and displeasure, and the idea that respect for the moral law is respect for ourselves as legislators.

Building on Derrida’s celebrated analysis of the term ‘supplement’, this chapter investigates the fundamental ambivalence of supplementary means of treaty interpretation. While the general philosophy of the Vienna Convention interpretive regime rests on the assumption of a hierarchy between the primary means set forth in Article 31 of the Vienna Convention and the supplementary means of Article 32, qualifying certain means as supplementary presumes that the primary interpretive means are somewhat lacking and in need of a complement. The chapter also focuses on the ‘danger’ of such supplement that has been highlighted in practice, namely, that supplementary means themselves need to be interpreted before they can be used in an interpretive inquiry, reinforcing the larger point made in the book that it is impossible to get an unmediated access to any signified. The chapter argues that since supplementary means are not comprehensively listed in the treaty interpretation regime, a virtually endless number of materials can be made relevant in treaty interpretation discourse through the channel of supplementary means.

How does one ascertain the object and purpose of a treaty? Can a treaty have more than one object and purpose? What does giving effect to the object and purpose of a treaty mean in practice? Despite such fundamental uncertainties surrounding them, the ‘object and purpose’ are widely resorted to in the practice of treaty interpretation. This chapter argues that the object and purpose doctrine is coextensive with a large amount of interpretive discretion. The identification of the object and purpose of a treaty a largely indeterminate process, and the assumption that the treaty makers necessarily want the object and purpose of their treaty to be implemented under all circumstances leaves the treaty interpreter with considerable normative power that can hardly be resisted given the very terms of the assumption. The chapter argues that consideration of the finality of a treaty cannot be an exercise in abstract logic, but meet the requirements of practical reason.

No philosopher is more strongly associated with deontological ethics or is a more canonical modern moral philosopher than Immanuel Kant. In this chapter, we focus on Kant, though we begin, after a brief introduction of Kant and his historico-philosophical significance, with Rousseau. Rousseau is best known as a political philosopher, but there are elements of his thought that have great importance for moral philosophy and its history and, especially, for Kant. Kant credits Rousseau as the source of his signature claim of the equal dignity of rational persons. And Rousseau’s conception of political society as an “association” that “defend[s] and protect[s] the person and goods of each associate with the full common force,” but where each “nevertheless obey[s] only himself,” has obvious resonances with Kant’s “kingdom of ends” in which all are governed by self-legislated law. At the same time, Rousseau offers important points of contrast to Kant. Whereas Rousseau’s emphasis is essentially social and political, Kant will attempt to argue for morality as a common law binding all agents that is grounded in practical reason alone. Rousseau, by contrast, points toward an alternative grounding in sociability that is reminiscent more of Grotius, Pufendorf, Smith, and Reid.

Jacobi argues that although Spinoza produced the most consistent rational system, its complete rational explanation leads to fatalism, mechanism, and atheism. The concern in this chapter is with how Jacobi stimulates Kant on issues of faith in relation to autonomy and practical reason (ethics), and how Kant’s “moral faith” seeks to avoid the pitfalls of mechanism while integrally linking faith with reason.

Prudence is the ability to determine the right course of action for a given situation. The virtue is fundamentally concerned with what we should do to achieve a desired objective, rather than what we should believe. Prudence is also a translation of Aristotle’s concept of phronesis (practical reason), which the Nicomachean Ethics defines as an “excellence of deliberation” (VI.9.9). In his formulation, Aristotle emphasizes the rightness of the ends being pursued, unlike several premodern and modern theories focusing only on the ability to attain desired ends, and which develop a somewhat uneasy relationship between prudence and virtue. Shakespeare makes the ethical challenges of prudence integral to The Merchant of Venice, a play featuring many deliberations over the means to such ends as happiness, wealth, friendship, and love. Throughout the play, Shakespeare takes a largely Aristotelian approach to prudence: characters who “hazard all” to gain noble ends are depicted as the most prudent, while the “shrewd,” who deliberate well but for immoral objectives, inevitably fail. Still, Shakespeare adds a final constraint to the virtue, suggesting that prudence is not a static trait but a dynamic effort to uncover one’s blind spots – and thus a virtue that few can hope to master.

This essay demonstrates the relationship between rights, natural law, and civic friendship by showing how the latter, the aim of law according to classic natural law theory, cultivates a culture of care for the other for one’s own sake, which is the basis of rights protections. It considers these connections in the teachings of key contributors to the classic natural law tradition, Aristotle and Aquinas, and engages their ideas with how rights are understood in modern liberal theory. The focus on the good regime of civic friendship responds to some contemporary concerns over the abstractness of human rights. While rights protections exist because the virtue of human beings cannot be depended upon, they still depend upon a standard of civic friendship that habituates citizens into regarding others as having absolute worth which finds its experiential origins in friendship.

The category of ‘human rights law’ is sometimes limited to bills and charters of rights on the model of the Universal Declaration of Human Rights and to the case law of courts interpreting and applying these legal measures. This chapter argues that the measures that realise human rights in the law are the everyday, unremarkable measures that make up the full corpus of legal materials directing what may, must, and must not be done. The argument explores how all sound positive law finds its source in the human goods through one of two modes of derivation: deduction or specification. These are the same two modes of positive law’s derivation from natural law, for the reach of human rights law is more or less coextensive with the reach of positive law and the human goods from which are derived human rights law are the same human goods from which are derived natural law’s practical principles and precepts.

This chapter outlines three positions on the desirability of a marriage of the natural law and natural rights traditions: (i) that natural law and natural rights may be united without any recourse to revelation; (ii) that natural law and natural rights may be united but only by recourse to revelation; and (iii) that any form of union between natural law and natural rights should be avoided as contrary to the common good and the well-being of the City of God. It is argued that the third position is the preferred on the grounds that the natural rights tradition is difficult to translate into a non-individualistic, communitarian framework. Social bonds and civic ties revolve primarily around mediating institutions such as the family and cultural, educational, and sports associations, not around the machinery of the state and abstract concepts. Unlike Bills of Rights that enumerate rights attached to individuals, the alternative Common Law tradition presupposes that human persons live in communities, that human life is relational, and that conflicts arise for adjudication when a clash of claims occur that need to be resolved with reference to some higher common good.