I don't have a strong opinion on the same-sex marriage debate. I have followed it casually, here and elsewhere. As a casual observer, I have had one nagging question that I haven't seen addressed, and is magnified by Eugene's post on the slippery slope in the same-sex marriage cases that he mentioned last week.

Here's my thought--the definition of marriage as one man and one woman seems somewhat arbitrary, which is why it is difficult to justify. The primary justification I can see is a Hayekian one of prudential deference to tradition unless there is an extremely strong case for rejecting it. I would distinguish this from what I would understand as a Burkean objection, which I would read as tradition being prescriptive, rather than prudential. But whether this is an accurate distinction is probably a debate for a different day.

So the question is, if you get rid of the "man-woman" prong as largely arbitrary, why does this not lead to getting rid of the "one-one" prong as well? It seems like the new line is just as arbitrary as the old one.

Now my sense is that the courts simply say that they are distinguishable, but don't say why. They seem to simply say that they are different. And as Eugene's post implies, merely saying they are different without saying why doesn't hold up to scrutiny later.

The difference, as is often the case, is that legislatures often draw arbitrary lines, especially under their police power. But courts should be able to articulated a principled basis for their decisions rather than an arbitrary legislative-style line-drawing.

As I said, I don't have strong feelings on this, so my question is purely intellectual--I'd just like to understand better whether a principled line can be drawn here or whether this is largely arbitrary line-drawing.

Update:

On rereading, it would probably have been more accurate to characterize the traditional one man-one woman definition of marriage as "conventional" rather than arbitrary ("arbitrary" may suggest a normative characterization that I did not intend), but I think that the general point of my query was apparent to readers.