Nagel on (Gottlieb on) Hobbes, getting the critical point:
What was distinctive about Hobbes’s theory, and what led to his being attacked as a moral nihilist, was his refusal to appeal to any concern for the good of others or the collective good as a basis for moral motivation. He demonstrated that the familiar rules of morality, which he called the laws of nature, are principles of conduct such that if everyone follows them, everyone will be better off. But the fact that everyone will be better off if everyone follows them gives no individual a reason to follow them himself. He can have a reason to follow them only if that will make him individually better off. And there is no natural guarantee that individual self-interest and the collective interest will coincide in this way. […] Hobbes concluded that although we all have a reason to want to live in a community governed by the moral rules, we cannot achieve this unless we bring it about that it is in each person’s individual interest to abide by those rules. And the method of doing that is to agree with one another to support a powerful sovereign with a monopoly on the use of force, who will use it to punish violators. Only then can each individual be confident that if he obeys the rules, he will not be laying himself open to assault and dispossession by others. Without the trust engendered by the knowledge that violators will be punished, civilization is impossible and individual self-interest — the same rational motive that supports morality — leads to perpetual conflict and constant insecurity. This is the famous Hobbesian state of nature, and Hobbes was most notorious for saying that in this condition, we are almost never obligated to obey the moral rules, because it is not safe to do so.
The identification of a collective optimum does no realistic theoretical work. Irrespective of the status of his concrete conclusion, Hobbes’ methodical principle is impeccable.