First, Sidgwick is considered to have offered the clearest exposition of the classic utilitarianism of Jeremy Bentham (1748–1832) and John Stuart Mill (1806–1873) to such an extent that he is often counted as a utilitarian himself. But second, it is his comparative assessment of egoism, utilitarianism, and intuitionism that remains most instructive. (“Egoism” is the moral system according to which we should always act in our own self-interest.)

Sidgwick examined both common sense moral principles and the main claims of all three systems and concluded that none is self-evident or certain according to intuition. He thought that utilitarianism could be useful when we do not know what to do and seek guidance, but that the basic principles of utilitarianism depend on intuition for their acceptance. But egoism also seems self-evident, and it often conflicts with utilitarianism. Sidgwick admitted that he could not resolve this contradiction.