This new book by Yale philosopher John Hare defends the thesis that what makes something morally obligatory is that God commands it, and what makes something morally wrong is that God commands us not to do it. (Hare writes in a footnote that, strictly speaking, there is an exception to this principle, namely God does not make it obligatory, by commanding it, to obey God’s command, but this is because the principle that God is to be loved, and  so to be obeyed, is “known from its terms.” He takes this issue up again later.) The Abrahamic faiths have made the connection between religion and the foundations of morality through the idea of God’s command. They have had to integrate two kinds of experience: The first is that God tells us to do something, or not to do something, and the second is that we have to work out for ourselves what to do and what not to do. None of these faiths have been able to dispense with either claim.

The difficulty has come in reconciling them. The concern of this book is that we remember to love God’s law and God’s command. Christians, in particular, must recall that the law and the command are the groundwork for the rest of the narrative of redemption. Psalm 119 is an extended expression of the gratitude of a people who would otherwise, without heeding God’s revelation, go astray like lost sheep. The relationship between this revelation of the law and command and our human nature is not that we should deduce how we ought to live from how we are by nature inclined to act, for our natural inclinations are a thorough mixture of what we should follow and what we should not. But God’s command to us fits our nature very well in the sense that it guides us in discerning which of these inclinations found in our nature we should embrace and which we should not. We also need discernment about what to take as a divine command. This book will tackle such issues by looking first not at abstract principles independent of religion, but at the narratives internal to the three Abrahamic faiths about what God and humans are like.

In Christian reflection on this, two main traditions have emerged: divine command theory and natural law theory. The book will, for the most part, conduct its argument in reference to the theories of particular philosophers and theologians rather than using those general terms like “divine command theory.” It’s not clear what we would be accountable to if we were discussing “divine command theory” unless by stipulation. There is no canonical text for the theory. It is better to be content with building up an understanding of how the various thinkers in these two traditions have held views partly similar to each other and partly different.

The first chapter proceeds by identifying three arguments by which we can establish various kinds of dependence relation of morality upon religion. They’re not original, and versions of them are pervasive in the literature. The first chapter takes versions directly or indirectly from Kant. The second chapter discusses what kind of thing a divine command is, and what its species are. The third chapter is about one typical disagreement between divine command theorists and natural law theorists. This is a disagreement about eudaemonism, the view that all our choices and actions are properly aimed at our own happiness. This is relevant for divine command theory because, if we make our moral choices for the sake of happiness, we do not need divine command as an answer to the question why we should choose what is morally right; we should do so in order to be happy. The fourth chapter is what Hare calls “deductivism,” the view that we can deduce our moral obligations from facts about human nature. This is relevant to divine command theory because, if we can deduce our moral obligations from facts about human nature, we do not need divine command to give us the content of the moral law. The fourth chapter has three sections: one on Scotus and his rejection of deductivism, a second on rejection of a form of deductivism in Robert Adams, and the third on the dispute about deductivism between R. M. Hare and Philippa Foot and Rosalind Hursthouse. In sum, the first half of the book is largely concerned with laying out a version of divine command theory and defending it against alternative theories.

The second half of the book relates the theory outlined in the first half to four new areas, the first three to theological accounts in the three main Abrahamic faiths. Chapter 5 is on Karl Barth, focusing on three themes: his particularism (his view that the paradigmatic divine commands are to particular people at particular times and places), his account of human freedom, and his discussion of how we know what divine command is being addressed to us. Chapter 6 is on DCT in Islam, Chapter 7 on DCT in Judaism, and Chapter 8 on evolutionary psychology, defending the claim that thinking of our moral obligations as produced by divine command helps us see how a moral conscience could develop in a way that is evolutionarily stable.

What ties this wide discussion together is the notion of God’s command. What emerges is that DCT and natural law are closer than one might expect. There remain differences between them, but the two are in many respects complementary. There is nothing incongruous in a divine command theorist saying that God’s commands fit human nature, or in a natural law theorist saying that God’s commanding is a necessary condition for a moral obligation. Nonetheless, the form of DCT defended in this book remains different in some key respects from the most familiar forms of natural law theory in the literature.

The first topic, then, is three arguments by which we can establish that morality depends on religion. Hare calls them the argument from providence, the argument from grace, and the argument from justification. The first two come directly from Kant, and the third only indirectly from Kant, but Hare’s argument is independent of him. Kant is not a major topic in remaining chapters, but his arguments are often good ones and he remains a key figure in moral philosophy.