[Medical] science was indeed powerful, but its self-understanding left much to be desired. It knew the human parts in ever-finer detail, but it conce… - Leon Kass

With his attractive picture of human flourishing, Aristotle offers lasting refuge against the seas of moral relativism. Taking us on a tour of the museum of the virtues — from courage and moderation, through liberality, magnificence, greatness of soul, ambition, and gentleness, to the social virtues of friendliness, truthfulness, and wit — and displaying each of their portraits as a mean between two corresponding vices, ­Aristotle gives us direct and immediate experience in seeing the humanly beautiful. Anyone who cannot see that courage is more beautiful than cowardice or rashness, or that liberality is more beautiful than miserliness or prodigality, suffers, one might say, from the moral equivalent of color-blindness.

For most Americans, ethical matters are usually discussed either in utilitarian terms of weighing competing goods or balancing benefits and harms, looking to the greatest good for the greatest number, or in moralist terms of rules, rights and duties, "thou shalts" and "thou shalt nots." Our public ethical discourse is largely negative and "other-directed": We focus on condemning and avoiding misconduct by, or on correcting and preventing injustice to, other people, not on elevating or improving ourselves. How liberating and encouraging, then, to encounter an ethics focused on the question, "How to live?" and that situates what we call the moral life in the larger context of human ­flourishing. How eye-opening are arguments that suggest that happiness is not a state of passive feeling but a life of fulfilling activity, and especially of the unimpeded and excellent activity of our specifically human powers—of acting and making, of thinking and learning, of loving and befriending. How illuminating it is to see the ethical life discussed not in terms of benefits and harms or rules of right and wrong, but in terms of character, and to understand that good character, formed through habituation, is more than holding right opinions or having "good values," but is a binding up of heart and mind that both frees us from enslaving passions and frees us for fine and beautiful deeds. How encouraging it is to read an account of human life—the only such account in our philosophical tradition—that speaks at length and profoundly about friendship, culminating in the claim that the most fulfilling form of friendship is the sharing of speeches and thoughts.

The truths modern science finds—even about human beings—are value-neutral, in no way restraining, and indeed perfectly adapted for, technical application. In short, as Hans Jonas has put it, modern science contains manipulability at its theoretical core—and this remains true even for those great scientists who are themselves motivated by the desire for truth and who have no interest in that mastery over nature to which their discoveries nonetheless contribute and for which science is largely esteemed by the rest of us and mightily supported by the modern state.