The basic difficulty is that the altruistic values that we acquire by social conditioning and perhaps by heredity are vague and open-ended. Primitively the premium is on kin, and primitively therefore the tribe in its isolation affords a bold boundary between the beneficiaries of one's altruism and the alien world. Nowadays the boundary has given way to gradations. Moreover, we are prone to extrapolate; extrapolation was always intrinsic to induction, that primitive propensity that is at the root of all science. Extrapolation in science, however, is under the welcome restraint of stubborn fact: failures of prediction. Extrapolation in morals has only our unsettled moral values themselves to answer to, and it is these that the extrapolation was meant to settle.
Today we unhesitatingly extrapolate our altruism beyond our close community. Most of us extend it to all mankind. But to what degree? One cannot reasonably be called upon to love even one's neighbor quite as oneself. Is love to diminish inversely as the square of the distance? Is it to extend, in some degree, to the interests of individuals belonging to other species than [our] own? As regards capricious killing, one hopes so; but what of vivisection, and of the eating of red meat?
One thinks also of unborn generations. Insofar as our moral standards were shaped by evolution for fostering the survival of the race, a concern for the unborn was assured. One then proceeds, however, as one will, to systematize and minimize one's ethical axioms by reducing some causally to others. This effort at system-building leads to the formulation and scrutiny of principles, and one is then taken aback by the seeming absurdity of respecting the interests of nonexistent people: of unactualized possibilities. This counter-revolutionary bit of moral rationalization is welcome as it touches population control, since the blind drive to mass procreation is now so counter-productive. But the gratification is short-lived, for the same rationalization would seem to condone a despoiling of the environment for the exclusive convenience of people now living.
It need not. A formulation is ready to hand which sustains the moral values that favor limiting the population while still safeguarding the environment. Namely, it is a matter of respecting the future interests of people now unborn, but only of future actual people. We recognize no present unactualized possibilities.
Thus we do what we can with our ultimate values, but we have to deplore the irreparable lack of the empirical check points that are the solace of the scientist. Loose ends are untidy at best, and disturbingly so when the ultimate good is at stake.
(W. V. Quine, "On the Nature of Moral Values," in Values and Morals: Essays in Honor of William Frankena, Charles Stevenson, and Richard Brandt, ed. Alvin I. Goldman and Jaegwon Kim [Dordrecht, Holland: D. Reidel Publishing Company, 1978], 37-45, at 44-5 [italics in original])
