Social conservatives like to draw an analogy between abortion and slavery, because it suggests that they are on the right side of both morality and history. Are they right?
There are, admittedly, some similarities. Both involve moral/philosophical propositions (people are not merely the property of another; a fertilized egg is a person) that are not susceptible of empirical proof or disproof. In both cases, public opinion was passionate and sharply divided. The two issues have been fought in both the judicial and political arenas. Finally, the majority of public opinion in both situations supported compromises that satisfied neither side.
Leaving aside the intellectual merits of the two arguments, however, there are two major differences which dictate a different result. The United States in 1861 was outside of the mainstream of world opinion on slavery; that is not the case with abortion. Second, permitting abortion is consistent with individual freedom, while slavery required the use of state power to deny freedom. Shouldn’t the presumption operate in favor of individual liberty in a political system that makes it an overriding value?