I turn now to questions concerning killing in war. I first rehearse Thomas Aquinas’s treatment of the conditions that must be met for a just war. Aquinas clearly differs from me in his belief that those with public authority are morally entitled to intend death as part of what is required for them to carry out their responsibilities. I argue, however, that even St Thomas is more restrictive with regard to intentional killing than are some contemporary Thomists.

In this chapter I address the problem of human suffering. After giving an account of the nature of suffering, I argue that suffering does not justify intending death. However, suffering needs to be understood within the larger story of Christ’s redemptive work.

In this Chapter I argue, contrary to Aquinas and modern day defenders, that capital punishment is unjustified killing. Capital punishment is not required by retributivism, and Aqunas’s arguments defending the practice are unconvincing.

This chapter critiques Judith Jarvis Thomson’s famous defense of abortion by addressing the question of ownership of the mother’s body. It then addresses the question of "vital conflict" cases: cases of abortion in which the mother’s life is in imminent danger.

In this chapter I address the killing of human embryos under three different kinds of circumstance. First are embryos in vitro; second, embryos that are a result of sexual intercourse but which have not yet implanted in a woman’s uterus; and third, embryos that have implanted in the wrong location, typically in the fallopian tube, and which thus cause a significant danger to the mother’s life if the pregnancy continues.

In this chapter I present the Core Argument for why intending death is always wrong. The argument gives reason to hold a sanctity-of-life view but does not depend on such a view.

Courage is the virtue of acting when we would rather not. This chapter looks at some of the classic situations where courage is needed, such as war and emergency response. It suggests that we need to show the sort of courage that comes from treating climate change as an emergency. Drawing on specifically Christian examples, we also consider the courage of the martyrs.

Prudence is the virtue of seeing things clearly. It has been notably central to Christian accounts of what it means to be a virtuous person, and to live a virtuous life. At the foundation of that lies the idea that to act well we have not only to understand the sorts of traditions that help us know what is good, but also to work on having an accurate account of the concrete situations we face. Much of what is offered as convenient solutions to climate change fail in the second way: these easy fixes simply aren’t realistic or accurate, as they cannot be implemented at the speed or scale we need. Drawing on the work of the philosopher Iris Murdoch, we call this sort of techno-optimism ‘fantasy’, and contrast it with the sort of imaginative response to the world as it really is that Murdoch championed, and which any successful response to climate change demands.

The virtue of temperance, or moderation, is central to a discussion of responding to climate change by showing restraint. In this chapter, we discuss the idea that temperance is not about despising goods or pleasures, but about ordering them, being willing to forgo lesser goods for the sake of greater goods. Attention to the need for temperance helps us to be realistic that the climate challenge we face does require some sacrifice, some letting go. Approaching that in terms of the ordering of goods helps us to find motivation: we do it for the sake of the things we love most, among which we might list God, the earth, human societies and other people, not least those who will come after us.

Justice is about giving people what they deserve and not depriving them of what is properly theirs. Justice enjoys a commanding position among the cardinal virtues, as that which is to be sought. Applied to human life, it might seem that justice is rather a weak aim: that we certainly would not want injustice, but that other things seem necessary for a flourishing human community, such as kindness and love. That is true, but justice is a necessary backstop, and one at which we are failing, when we think about how climate change is already depriving people – indeed some of the poorest people – of land and homes.