Philosophy
Foot grounds moral evaluation in natural facts about the life, needs and characteristic activity of human beings.
What counts as a good specimen depends on how that kind of creature lives: wolves need to hunt in packs, honeybees need to communicate, and humans need to cooperate. Foot argues that the standard comes from the species' way of life, not from anyone's preferences.
On Foot's view, a person who lies as a matter of habit is defective in the same sense as a bee that does not pass on information to its hive. Human life depends on people generally keeping certain shared virtues, so failing at them is a failure to be what a human should be.
Beginners in philosophy are often taught that facts never settle what is good. Foot denies this. If 'good' describes how well a living thing fits its kind's way of life, then moral judgements can be true, made true by facts about life. This sets her against the long tradition holding that values are projections of feeling.
Foot treats moral goodness as one aspect of practical reason, not as something added on top of it. Earlier attempts to show that morality is rational failed, she argues, because they began with too narrow an idea of reason, roughly reason as self-interest.
Foot's argument for following ethical judgements asks who could have a reason to act against the life-form of their own species. Once you see what humans need in order to live well, you have a reason to act well, and that reason is also a motive.
One objection says that a particular just act can be costly to the person who does it. Foot replies that judging just acts one at a time misses the value of being a just person in general. The trait can be worth having even when a single instance of it costs you.
Among philosophers who revived the ethics of virtue, some think it must be cut loose from the ancient idea that a creature's nature sets its good. Foot thinks it may not need to be. She reverses her own earlier view that morality gives reasons only to people who happen to have certain optional desires.
Foot argues that there is a special kind of evaluation that applies only to living things, judged as members of their species. An owl that cannot see in the dark is defective as an owl, and she holds that moral judgements about people are evaluations of the same kind.
On Foot's account, being rational means weighing different kinds of considerations well, including self-interest, other people's welfare, and promises. No rule says in advance which kind must win in a particular case. Practical wisdom is skill at this weighing, not a single formula.
Because vice is a defect in a human being, Foot suggests that there is a strong sense in which evil people cannot be truly happy. On this view, happiness in its deep sense is tied to living well as a human, not merely to feeling satisfied. Her discussion of virtue and happiness ends by answering a famous rejection of morality as such.