It may be shown, I think, that the Utilitarian estimate of consequences not only supports broadly the current moral rules, but also sustains their generally received limitations and qualifications: that, again, it explains anomalies in the Morality of Common Sense, which from any other point of view must seem unsatisfactory to the reflective intellect; and moreover, where the current formula is not sufficiently precise for the guidance of conduct, while at the same time difficulties and perplexities arise in the attempt to give it additional precision, the Utilitarian method solves these difficulties and perplexities in general accordance with the vague instincts of Common Sense, and is naturally appealed to for such solution in ordinary moral discussions. It may be shown further, that it not only supports the generally received view of the relative importance of different duties, but is also naturally called in as arbiter, where rules commonly regarded as co-ordinate come into conflict: that, again, when the same rule is interpreted somewhat differently by different persons, each naturally supports his view by urging its Utility, however strongly he may maintain the rule to be self-evident and known a priori: that where we meet with marked diversity of moral opinion on any point, in the same age and country, we commonly find manifest and impressive utilitarian reasons on both sides: and that finally the remarkable discrepancies found in comparing the moral codes of different ages and countries are for the most part strikingly correlated to differences in the effects of actions on happiness, or in men's foresight of, or concern for, such effects. Most of these points are noticed by Hume, though in a somewhat casual and fragmentary way: . . .
(Henry Sidgwick, The Methods of Ethics, 7th ed. [Indianapolis: Hackett Publishing Company, 1981], bk. IV, chap. III, sec. 1, pp. 425-6 [first published in 1907; 1st ed. published in 1874])
Note from KBJ: Richard A. Posner has argued that wealth maximization is the best theory of the common law. Richard A. Posner, Economic Analysis of Law, 7th ed. (New York: Aspen Publishers, 2007), 25. He calls this "positive [as opposed to normative] economic analysis of law." Here we find Sidgwick arguing that utilitarianism (i.e., the principle of utility) is the best theory of commonsense morality. We might call this "positive [as opposed to normative] utilitarianism." Suppose Sidgwick is correct. Nothing follows concerning the acceptability of utilitarianism. That utilitarianism is latent in commonsense morality does not entail that it ought to be, much less that it should be our guide as we decide what to do. By the same token, just because wealth maximization is latent in the common law does not entail that it ought to be, much less that it should guide judges, legislators, or other policymakers. Perhaps policymakers should pursue some other goal besides (or in addition to) efficiency (such as justice).