One Another’s Equals: The Basis of Human Equality by Jeremy Waldron Belknap Press/Harvard University Press, 264 pp., $29.95

All men are created equal—but in what sense equal? Obviously not in the sense of being endowed with the same attributes, abilities, wants, or needs: some people are smarter, kinder, and funnier than others; some want to climb mountains while others want to watch TV; and some require physical or emotional support to do things that others can do on their own. And presumably they are not “equal” in the sense of demanding identical treatment: a father can give aspirin to his sick child and not his healthy one without disrespecting the equality of his children. Rather, all humans are said to be equal in what philosophers call the “basic,” “abstract,” “deep,” or “moral” sense of equality. We are all, in some fundamental sense, and despite our various differences, of equal worth, demanding, in Ronald Dworkin’s famous phrase, “equal concern and respect.”

For many of the founding fathers, the principle of basic equality was consistent with some people being the property of others; in 1776 the abolitionist Thomas Day remarked that “if there be an object truly ridiculous in nature, it is an American patriot, signing resolutions of independency with the one hand, and with the other brandishing a whip over his affrighted slaves.” A commitment to basic equality was also apparently consistent with “free” women being legally excluded from civic life. Today, the US’s commitment to basic equality is apparently consistent with not only enormous socioeconomic inequality, but also enormous inequality of opportunity, much of it still determined by race and gender.

The seeming compatibility of basic equality with gross material and social inequality has led more than one critic (Marx most obviously) to wonder if talk of being “created equal” is a hollow spiritual promise designed to placate those suffering from earthly misery. That basic equality is not such a hollow promise—that it means something substantial, and that it is crucial to our political morality—is the central thesis of Jeremy Waldron’s One Another’s Equals.

In the postwar period, political philosophers have been much concerned with equality, though their concern has generally focused on what Waldron calls “surface-level issues” of equality: whether, as egalitarians, we should be aiming for equality of well-being, equality of material resources, or equality of opportunity. (By calling such questions “surface-level” Waldron doesn’t mean they are superficial; he calls them “some of the most intractable problems of political philosophy.” He means they take for granted that some sort of egalitarianism is right.)

Meanwhile, less has been said in the postwar period about what might justify a commitment to basic equality: why we should be some sort of egalitarian at all. Writing in 1962, Bernard Williams suggested that our common capacities to suffer and to love were the grounds of universal human equality. A year later, John Rawls proposed that what he…