Anyone who has ever attended a cocktail party or taught a college course in ethics or political theory is likely to be familiar with the following line of argument. People in our society disagree about the morality of, for example, abortion, pornography, or homosexual conduct. The fact of moral disagreement shows that that there is no objective moral truth about these matters; there is merely subjective opinion. Further, no one has a right to impose his merely subjective moral opinions on those who happen not to share them. Therefore, laws prohibiting, discouraging, or even disfavoring abortion, pornography, or homosexual acts unjustifiably violate people's freedom.
A moment's reflection, however, brings to light a host of fallacies in this line of reasoning. Perhaps the most damning is its illicit inference of an absence of objective moral truth from the existence of moral disagreement. If Alex claims that slavery, for example, is morally wrong, and Bertha disagrees, then the fact of Bertha's disagreement does not mean that Alex's claim is false. True, Alex might be mistaken about the moral wrongness of slavery, but the mere fact of Bertha's disagreement is not a sufficient reason for thinking that he is mistaken. After all, Bertha also might be mistaken. If Charlie comes along, not yet having formed his own opinion about slavery but wishing to form a sound opinion, he will want to consider Alex's arguments for slavery's immorality, together with Bertha's counterarguments, before reaching a judgment. Charlie could not reasonably conclude from the sheer fact of disagreement between Alex and Bertha that the matter admits of no objective moral truth. Moreover, such a conclusion remains unreasonable if Alex and Bertha shift from debating slavery to arguing about abortion, homosexual conduct, pornography, recreational drug use, or any other currently contested moral issue.
(Robert P. George, "Law, Democracy, and Moral Disagreement," review of Democracy and Disagreement: Why Moral Conflict Cannot Be Avoided in Politics, and What Should Be Done About It, by Amy Gutmann and Dennis Thompson, and Legal Reasoning and Political Conflict, by Cass R. Sunstein, Harvard Law Review 110 [May 1997]: 1388-406, at 1388-9)
