Chapter 2 analyses Hobbes’s ‘doctrine of necessity’, which was famously so termed by Hobbes himself in his debate with Bishop Bramhall. It argues that by means of this doctrine’s basis in the natural sciences Hobbes transformed natural law from an idealist to a pragmatic enterprise, from one based on natural rights to one characterized by the pragmatic employment of principles of necessity. The chapter discusses Avicenna’s metaphysics of existence, through which he described ‘nature’, which gives precedent to what exists in the material world and depends on the necessitarian principle that ‘whatever exists is necessitated by another’. Similarities between Avicenna’s metaphysics and Hobbes’s are analysed, and in respect of the former the capacity of the doctrine of necessity to sustain a metaphysical framework for philosophy and politics is identified.

This chapter examines the earliest natural rights theories in order to analyse philosophical connections between natural and human rights, concerning: scepticism, metaphysical dualism, and the authority of rights. First, the chapter studies Albert the Great’s principles of right and how he understood nature to be reason. Next, analysis of the main tenets of Henry of Ghent’s metaphysics, and his exposition of the soul’s property over one’s body, show that Neoplatonist dualism was fundamental in the development of the first natural rights theories. The philosophical solution to the poverty controversy, of human beings’ natural rights to use material goods, that Hervaeus Natalis proposed became the law of the Church when the Pope incorporate it in the bull, Cum inter nonnullos (1323). Hervaeus continued the metaphysical dualism of Henry and argued that natural rights endowed reality with normativity and hence authority. The chapter concludes by relating this intellectual history to contemporary rights theories. Natural and human rights are identified as a form of public reason that sometimes assists, other times substitutes for, individual right reason and judgement about morality.

Chapter 7 examines medieval theories of the first cause of evil. Although Augustine denied that something good is the cause of evil, medieval thinkers routinely attributed to him the view that something good – the will understood as a power of the soul – causes something evil. The majority of the thinkers considered in this chapter use Aristotle’s notion of accidental causality to argue that the will can cause evil not per se – that is, not intending evil as evil – but incidentally. Nevertheless, if the will causes evil, they face the dilemma that a good will cannot cause evil at all, and an evil will cannot cause the first evil will. Medieval thinkers deal with this dilemma in different ways. For example, Bonaventure and others hold that the created will is naturally defectible, and hence not entirely unflawed, and so it can do evil. Aquinas argues that the will causing evil for the first time presupposes a momentary nonculpable deficiency, which becomes culpable at the moment of the evil choice. For Scotus, the will is so free that it can do evil even if it is unflawed. Although all these views trace evil to the will as its cause, they hold that evil is ultimately unexplainable.

Chapter 10 studies theories of demonic obstinacy, the state in which the fallen angels or demons are unable to avoid sinning and have a limited ability to do good. The external cause of obstinacy is God’s refusal to offer them the grace of repentance and of justification. Beginning with Aquinas, theologians searched in addition for an internal, psychological cause of their obstinacy – a great challenge, given their shared belief that the angels’ will is by nature oriented to the good. Aquinas traces their obstinacy to the fixity of their cognition, and Henry of Ghent to the forcefulness of their will. Certain Franciscan thinkers explain the demons’ obstinacy by means of a divine intervention, binding their will to evil (Olivi), causing their immoderate self-love (Scotus), causing in them a habit of wickedness (Auriol), or even causing in them hatred of God (Ockham). Durand of St. Pourçain returns to the standard account prior to Aquinas, which explains the demons’ obstinacy by a divine decision, with no reference to their psychological condition. In addition to the cause of obstinacy, theologians discussed whether the demons, though necessarily obstinate, are nevertheless free.

Chapter 9 examines explanations of the angelic fall by voluntarists and thinkers holding an intermediary theory of free will. These nonintellectualist accounts agree – contrary to intellectualists – that there was deficient willing before there was deficient cognition. For some voluntarists, the discussion of angelic sin serves above all as confirmation of their own theories of free will (e.g., Henry of Ghent) or as proof that their adversaries are wrong (e.g., John Pecham). Others go further and try to give a plausible account of how the evil angels could intentionally make their choice (Peter Olivi), and to explain how their will could be defective while their cognition was unflawed (Duns Scotus). Among thinkers professing an intermediary theory of free will, the chapter considers Giles of Rome, whose account of angelic sin fits nicely with his general theory of the relation of ignorance and evil, and Peter Auriol, whose explanation of angelic sin does not sit comfortably with his theory of free will.

Chapter 3 is about late thirteenth-century voluntarist theories. It discusses three ecclesiastical condemnations of philosophical propositions, one in 1270 and two in 1277. Among the censured propositions are some that express intellectualist views about intellect and will. The chief part of the chapter gives a comprehensive account of Henry of Ghent’s theory of free will, the most influential theory at the time. At its core is the belief that the intellect does not control its act, so all control of a person’s acts must be traced to the will. For Henry, the fact that only the will, but not the intellect, controls its acts implies that the will can choose even contrary to the intellect’s judgment of what is best to choose. The will’s relative independence from the intellect, in turn, implies for Henry that the will moves itself to its act, while the cognized object (the desirable object presented by the intellect) is no more than a presupposition for the will’s act – a so-called “causa sine qua non.” The chapter also examines in some detail Peter Olivi’s theory of free will, which resembles Henry’s on many points. It ends with a brief mention of other voluntarist thinkers.