Herbert of Cherbury and the Cambridge Platonists held that what morality requires, before all else, is the pursuit of perfection; but they had different understandings of the difficulties of the pursuit. Herbert thought that we must increase moral knowledge in order to increase perfection; the Platonists saw insufficient resolution, not ignorance, as the obstacle to virtue. For them we need to strengthen our will so that we can resist temptation and live as we all know we should. Descartes also took the view that the cultivation of strength of will is the path that we must take to achieve virtue. But he presented his view as a second-best morality, an expedient needed because action is unavoidable even though we do not know that we are acting rightly. If we could now pick the fruit of the tree of knowledge, the will, guided by the intellect's clear and distinct perceptions, would necessarily – and without struggle – choose the right course of action.

Descartes could take his morality to be an interim measure because he optimistically thought that research would one day yield enough truth to direct action with certainty. Benedict Spinoza (1632–77) and Nicholas Malebranche (1638–1715) did not share his optimism. Agreeing that perfection is our goal, they held that it would be attainable only if we could know all that God knows, which we plainly cannot.

Richard Cumberland (1631–1718), bishop of Peterborough, saw a profound threat to Christian morality and religion in what he called the “wicked doctrines” of Hobbes. A number of pamphleteers before him had taken potshots at the outworks of the Hobbesian fortress. Cumberland's De Legibus Naturae (1672) was the first attempt to mount a full-scale philosophical assault on the whole massive structure of Leviathan.

To counter Hobbes, Cumberland found it necessary to put forward a new theory of morality. Experience, he thought, teaches us that we are required to work together for the greatest possible happiness. Because he asserted this particular basic principle Cumberland has long been thought of as the first utilitarian. If the characterization is overly simple, there is still a substantial amount of truth in it. But Cumberland's reasons for asserting the principle were very different from those that led the later writers who called themselves utilitarians to their version of it. They sought a publicly acceptable rationale for political and social reform. Cumberland saw his principle as the only one that could embody a morality common to God and human beings – and that, in so doing, could rebut Hobbes's denial of the possibility of such a morality. He was not a reformer. But he was the first philosopher who created an important new ethical theory because he thought it was morally required in order to defeat voluntarism.

Kant invented the conception of morality as autonomy. I use the notion of invention as Kant himself did in an early remark. “Leibniz thought up a simple substance” he said, “which had nothing but obscure representations, and called it a slumbering monad. This monad he had not explained, but merely invented; for the concept of it was not given to him but was rather created by him.” Autonomy, as Kant saw it, requires contracausal freedom; and he believed that in the unique experience of the moral ought we are “given” a “fact of reason” that unquestionably shows us that we possess such freedom as members of a noumenal realm. Readers who hold, as I do, that our experience of the moral ought shows us no such thing will think of his version of autonomy as an invention rather than an explanation. Those with different views on freedom and morality may wish that I had called this book The Discovery of Autonomy. We can probably agree that Kant's moral thought is as hard to understand as it is original and profound. Systematic studies from Paton and Beck to the present have greatly improved our critical grasp of his position. In this book I try to broaden our historical comprehension of Kant's moral philosophy by relating it to the earlier work to which it was a response.

Many of the writers with whom I have been concerned so far held that morality is tied in some way or other to salvation. If they did not think that morally decent behavior would by itself lead to or guarantee salvation, they took it to be at least a necessary condition of salvation, or a sign of it. Either you had to behave decently in order to become qualified for saving grace, or you could earn eternal life by moral goodness, or if you were of the elect you would show it by morally good behavior. Even the natural lawyers, reticent on principle about such matters in their jurisprudential treatises, had salvation somewhere in mind: witness Pufendorf's claim that dedication to performance of imperfect duties in the right spirit may win us merit – and not only in this life (Chapter 7.iv). Extreme antinomians, indeed, may have held that if you are saved, then anything you do counts as good, and morality is quite beside the point. But such views drew philosophical consideration, if at all, only to be rejected. Philosophers with serious religious convictions tended to think that there had to be some connection between morality and salvation.

For atheists, of course, there was no issue here. The so-called libertines in France during the first half of the seventeenth century proposed a wide variety of unorthodox standpoints, with atheistic morality among them.

“Error is the cause of men's misery” So Malebranche opens his great treatise, The Search after Truth, published in 1674–5. The contrast between this and the opening reference of Grotius's Law of War and Peace to controversy as the problem to be handled by morality concisely indicates the basic difference between the natural law thinkers and the rationalist moral philosophers of the seventeenth century. What united the former, I have argued, was acceptance of a problematic centering on the permanence of conflict. What unites the latter is the thesis that ignorance and error resulting from failure to use our reason properly are what stand between us and a life of harmony and virtue.

The modern natural lawyers held that by reasoning from observable facts we can find out how to cope with the moral and political problems that beset our lives. Experience gives us the evidence we need in order to infer that God exists and cares for us. Part of what we learn from it is that God has made the proper structure of our common life independent of any larger cosmic scheme. Even if there is some divine harmony in the universe, we cannot appeal to it in determining how we ought to live. Once we understand that God governs us, the observable facts about ourselves in this world provide all the rational basis there can be for working out our proper direction.

Thomasius's rejection of servility in our relation to God is a late articulation in Germany of an attitude that found full voice earlier in England. “A right knowledge of God,” John Smith wrote in the middle of the seventeenth century, “would beget a freedome and liberty of soul within us, and not servility” (Discourses, p. 28; see also pp. 362, 364, 424). “Reverence God in thyself,” Benjamin Whichcote exhorted his readers, “for God is more in the mind of man, than in any part of this world besides” (Patrides, p. 333, no. 798). Ralph Cud worth quoted Athanasius in order to assert that “God was therefore incarnated and made man, that he might deify us” (Patrides, p. 101). From the 1640s on, these three formed part of a group engaged in a radical rethinking of Protestantism. They all agreed with Smith that “right knowledge of God” is indispensable to morality as well as religion. But the increase of knowledge was not, for them, sufficient for morality. What is centrally required is exercise of the virtues of love; and we are called to perfect ourselves in that exercise.

Like many others who contributed to the development of thought about morality, these thinkers were responding to religious controversies that were tearing their society apart. Sectarian Calvinism was swamping out the Thomism that Hooker had thought foundational for a national church.

Expressing one's opinions during the eighteenth century involved considerably more risk in France than in Germany or Britain. In Prussia a king could exile a professor; in England the orthodox could block a promising ecclesiastical career; in France the government could jail, torture, and execute those it disliked. Censors kept a watchful eye on French publications. The standards for licensing were intended to serve the needs of the royal government and the hierarchy of France's Roman Catholic Church. The licensing laws failed, however, to stop the flow of criticism. Attacks on all aspects of the established regime were published anonymously, or outside the country, or inside it with falsifications about the printer. They were addressed to the public at large, not only to the learned. We do not know how many readers they reached. But it seems clear that the more oppressive the political and religious authorities were, the more numerous and vehement became the books denouncing them. Writers went to prison or left the country, but they did not stop criticizing the powers whose threats could literally endanger their lives.

The chief concern of those who wrote about morality in prerevolutionary France was not with theory but with the hope, or threat, of change. In England, Scotland, and some of the German states, clergymen and professors produced original and important moral philosophy.

I have argued that the voluntarist natural lawyers tried to keep God essential to morality while confining his role in it to his initial willful act of creating it. Machiavelli and Harrington did without God in establishing their principles, though they thought a stable republic needed a civil religion. Montaigne explored the possibility of morality without religion, and his follower Charron made some effort to create a systematic naturalistic theory. Although Hobbes worked out such a system quite fully, he retained a marginal role for God in transforming the dictates of prudence into genuine laws; and however tempting it is for us to read Spinoza as a wholehearted naturalizer of morality, his own understanding of the universe was profoundly religious. Mandeville gave a natural history of morality, only to add to it an account of a demanding principle that has something to do with the divinity. No one believed he meant that part of what he said, and in any case it is plain that he was more interested in outraging public sentiment than he was in presenting a serious and thorough naturalistic philosophical account of human life.

David Hume (1711–76) intended to give just such an account. He made very clear, moreover, his belief that religion is morally and politically detrimental to society and human happiness. He did not urge the establishment of a civil religion for the masses.

At the core of the moral philosophy of Immanuel Kant (1724–1804) is the claim that morality centers on a law that human beings impose on themselves, necessarily providing themselves, in doing so, with a motive to obey. Kant speaks of agents who are morally self-governed in this way as autonomous. He took the term from the political thought of the seventeenth and eighteenth centuries, in which it was used in discussions of the idea of states as self-governing entities. I have indicated that the idea of moral self-governance goes back at least as far as St. Paul's assertion in Romans 2.14 that the gentiles are “a law unto themselves.” Kant understood the idea in a radically different way. His view of morality as autonomy is something new in the history of thought.

I do not propose to summarize Kant's mature moral philosophy or to engage in exegesis or assessment of it. Assuming the reader's familiarity with his view, I address two topics that have received much less attention in the literature than the structure and adequacy of the theory. In this chapter I offer an account of how Kant came to take the first major step toward his view of morality as autonomy. In the next chapter I discuss some of the ways in which Kant's mature moral philosophy is related to the views of his seventeenth- and eighteenth-century predecessors.

In rejecting natural law theory, Montaigne was rejecting the dominant European understanding of universal morality. During the fifteenth and sixteenth centuries all the universities taught their students the basic points of the theory; and it was important outside the academy as well. In 1594 the Protestant Richard Hooker produced a magnificent restatement of Thomistic natural law doctrine in order to justify, against Catholics and Calvinists, his claim that the English government could rightly determine what its churches taught and how they were to be organized. Sixteenth-century Spanish Catholic theologians were prolific sources of commentary on both intellectualist and voluntarist theories of natural law. Their greatest successor was Francisco Suarez, whose early seventeenth-century synthesis was designed to support his efforts to justify papal supremacy over all baptized Christians, including such heretics as King James I, and to defend tyrannicide. Hooker addressed a local issue and was influential only in England. Suarez spoke to problems of international order, and was read everywhere.

Hooker restated the Thomistic belief that under a divine supervisor all things follow laws directing them to act for the common good of the universe as well as their own, and that natural law directs us in particular to both ends equally. Quietly incorporating some elements of voluntarism, he tried to make his position acceptable to Calvinists as well as to members of his own church.

Which comes first in morality, law or love? Moral philosophy after Grotius was deeply shaped by this issue. No one denied that both law and love have a place in morals, and even those who put law first could, with Pufendorf, allow that love, as the only source of merit, has a unique importance. The priority of law is often associated with a voluntarist view of God, and the priority of love with opposition to voluntarism. Law comes first for those whose main concern is with social order, while those who give the prize to love focus on individual character. The natural lawyers did not think they needed to say much about love once they had made theoretical room for it in imperfect duties. The theorists of love had to be a little more explicit about law. In particular they had to show how to understand concepts embedded in ordinary morality that seem tied to a law-centered approach – concepts of rights and duties and obligations. But Cumberland seemed as able as Pufendorf to give definitions from which to derive his system. How could one get a purchase on the disagreement? One might, of course, show that some particular theory contained internal problems; but to get beyond that, one would need to have a way of assessing the initial premises.

Attempts to avoid the morally unpalatable consequences of Locke's empiricist ethics were at the core of the development of British moral philosophy during much of the eighteenth century. Shaftesbury kept a deity in his universe to ensure its moral harmony, but he most emphatically held that there was no need to appeal to divine laws and threats to explain how people can live decently. He tried to show that Locke's voluntarist ethics is undercut by our possession of a moral faculty that enables us to govern ourselves. Desires and passions are, for him as for Locke, blind forces caused by, but not containing, representations of goods and ills. The moral faculty gives us a special feeling of moral approval that is aroused by a harmonious balance of the motivating forces in the soul and then in turn reinforces that balance. If this was a way around Locke, it posed problems even for those who shared Shaftesbury's moral revulsion at Locke's reductionist ethics of command, threat, and obedience. Shaftesbury sometimes presents the moral feeling as a mere sentiment, causally interacting with ideas and feelings; but more deeply and persistently he treats it as revealing eternal truths. The one reading points toward a naturalistic view of morals which the other reading denies. Theories of both kinds were proposed early in the century.

Barbeyrac tells us that Bacon was a major influence on Grotius, and Cumberland claims that his own work answers Bacon's call for empirical investigation of morals. We have seen how important the empiricist outlook was for both Grotius and Cumberland; but Bacon held views that neither would have accepted. In his “Confession of Faith” he declared his belief

Bacon was not alone in combining empiricism, voluntarism, and the belief that pride is what moves us to insist that we must be able to understand God's commands by our own lights. Pufendorf's system presents the fullest modern exposition of the implications for morality of a view like this, and Locke recommended Pufendorf's work for the education of any gentleman's son.