Liberal or Social Democrat?

Is there a difference between a liberal and a social democrat that amounts to a distinction? If there is, is it a distinction with merit? Michael Walzer is a social democrat; it is an honorary badge. For a long time, he wore his badge while driving an antique Volvo—the second-hand car for mature social democrats. Sidney Morgenbesser, a master of fine and funny distinctions, tried to answer our question with a quip: A liberal believes money should be taken from the very rich and handed over to the poor. But he stands exactly at the point at which no money should be taken and no money should be given. In contrast, the social democrat believes she, too, has to give money.