George Weigel at National Review Online takes a philosophical look at the efforts to redefine marriage -- and identifies recent historical examples to support his argument:

...modern totalitarian systems were, at bottom, attempts to remake reality by redefining reality and remaking human beings in the process. Coercive state power was essential to this process, because reality doesn’t yield easily to remaking, and neither do people. In the lands Communism tried to remake, the human instinct for justice — justice that is rooted in reality rather than ephemeral opinion — was too strong to change the way tastemakers change fashions in the arts. Men and women had to be coerced into accepting, however sullenly, the Communist New Order, which was a new metaphysical, epistemological, and moral order — a New Order of reality, a new set of “truths,” and a new way of living “in harmony with society,” as late-bureaucratic Communist claptrap had it.

The 21st-century state’s attempt to redefine marriage is just such an attempt to redefine reality — in this case, a reality that existed before the state, for marriage as the union of a man and a woman ordered to mutual love and procreation is a human reality that existed before the state. And a just state is obliged to recognize, not redefine, it.

Moreover, marriage and the families that are built around marriage constitute one of the basic elements of civil society, that free space of free associations whose boundaries the just state must respect. If the 21st-century democratic state attempts to redefine something it has neither the capacity nor the authority to refine, it can only do so coercively. That redefinition, and its legal enforcement, is a grave encroachment into civil society.