A couple of hundred people squeezed into a warm room Thursday to see how the state might frame the definition of marriage.

More than a dozen speakers testified before a state Senate panel about a proposed amendment to the Pennsylvania Constitution that says:

"No union other than a marriage between one man and one woman shall be valid or recognized as marriage or the functional equivalent of marriage by the Commonwealth.''

The italics are mine. Some of the backers have taken to calling this a "marriage protection amendment," and after hours of testimony, I was still at a loss to figure out how this does that.

After almost 14 years of marriage, my wife and I welcome all the help we can get, but least among our concerns is more people wanting to embrace the institution.

Anyway, a remarkable amount of time at this hearing was spent talking about all the things this amendment won't do.

It won't change current law. The state Legislature passed a bill more than a decade ago banning same-sex marriages and any recognition of such unions performed outside our borders.

The proposed amendment also won't do anything to weaken domestic violence protections extended to co-habitants outside of marriage, or stop employers from offering same-sex benefits, or stop gay couples from adopting children, its proponents argued.

Opponents don't buy that, but even if proponents are correct, that still leaves the question: What is this amendment for?

At bottom, it is insurance against the state Supreme Court ever overturning the ban on gay marriages. One of the more imaginative arguments in favor of the amendment was made by Randy Lee, a law professor at the Widener University School of Law. A 50-year-old father of six, Mr. Lee likened the idea of equating gay unions with marriages to an unfair trade practice.

"You can't put a picture of corn on a can of peas and sell it as corn,'' he said.

No, but we call a lot of things marriages, and half of them end in divorce. Las Vegas, the desert city built by losers, proudly endorses thousands of shaky matrimonial decisions each year. Every magazine stand offers a running tally of tag-team celebrity romances.

Yet that is not the field of battle where the so-called "marriage protection amendment'' makes its stand. Nobody is talking about making divorce more difficult. This is about making sure no gay couple, no matter how long they've been together, gets a state document recognizing a commitment equivalent to a marriage.

Nobody at the hearing mentioned the word "sin'' during the hours I listened, but it struck me, not for the first time, that this debate is not about gay sex. That can continue. This is about trying to prevent what is seen as unnatural love. That's what is feared.

I'm still at a loss to see what a married couple should fear about the state calling another committed connection a "civil union.'' It's not like my church has blessed it, and I can still tell the difference between sugar and Equal. On this, I'm off the reservation.

"At a time we should be engaged in doing all we can to strengthen the family, we are facing cultural forces that want to so water down the definition of marriage that it could apply to any human relationship, or no relationship at all,'' Catholic Bishop David Zubik testified.

I share that desire for strong families. So did nearly all in the audience. Opponents of Senate Bill 1250 silently wore buttons that said "value all families.''

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The morning after the hearing, I called Mr. Lee. A key issue for him is the need for the state to draw clear distinctions between different kinds of relationships because they may need to be regulated in different ways.

"Two guys, they can commit themselves to one another,'' he said. "They don't need a state definition of marriage to figure out what their relationship is.''

A lot of couples who live together say the same thing. But there is something about the institution of marriage that people in love continue to value. That may be the only thing that unites everyone in this argument. If anyone can get past that irony, that's the good news.