As a nature writer, I'm always interested when a columnist or politician claims to speak for "nature." As a gay Portlander, I'm especially amazed to hear that "nature" has passed judgment against me.

A religious activist here in Oregon keeps getting anti-gay initiatives on the ballot, but he hardly seems the paragon of nature. True, he's got a wife, but in news photos he looks portly (Is that a natural effect of poor diet? Or is it unnatural, a violation of what his body really needs?). And I know he travels around in an automobile (hardly produced by nature) and uses money (also not natural). In fact, his heterosexual monogamy itself might be open to question. Didn’t natural selection design men to propagate their genes indiscriminately? Yet I don't hear him criticize monogamous marriage as unnatural.

So when cultural conservatives campaign to defend marriage by arguing that gay folks are against nature, I wonder what that means. Especially since, as a composting, hiking, not-overweight sort of person in the Northwest, I feel that I’m living in a better-than-average way, although, of course, I'm still a typical American who uses far too many of the world's resources.

The more I think about it, the more I see that the meaning of the word "nature" itself is a huge muddle.

Here's the nub of the confusion: "Nature" is a shifty word. Sometimes it is used to declare an ideal of how things ought to be — natural. But this is the opposite of what we usually mean by the word, which is how things are. Gay people often defend themselves by referring to nature in this more common sense: "Unnatural? Hey, this is my nature! I'm not going to force myself to go against it." It is true that homosexuality is a universal, if minor, part of human experience and culture. It is even widespread in the animal world, so it is natural in that sense.

But too often, people dress up their folkways as "what nature wants" or even "what God wants," failing to recognize that our perceptions of these standards change as culture changes. I'm 54, and I can remember arguments that women were "naturally inferior" to men, and that mixed-race marriages and ending segregation were unnatural. In my childhood Baptist church, these cultural constructs were defended from the Bible, as God's will.

Responding to last November's Massachusetts Supreme Court decision affirming gay marriage, newspaper op-eds have ceaselessly continued this muddling of nature, God and culture. The conservative Massachusetts Family Institute proclaimed "the biological reality that marriage is the union of a man and a woman," apparently forgetting that history shows marriage to be a social arrangement that changes almost by the decade. It's culture, not nature.

Former Moral Majority spokesman Cal Thomas has taken the other tack, informing us that "Marriage...was established by God" — despite the wildly differing forms of marriage that have been divinely blessed since the time of the biblical Solomon, a man who kept multiple wives.

Syndicated columnist Kathleen Parker has woven all the confusions together in my morning paper, capitalizing nature and making it a stand-in for God: Heterosexual unions embody a "superior natural order... which cannot be disputed," she writes. But she also acknowledges the apparent "naturalness" of those poor gay folks, since they didn't choose to be innately gay. She can't figure out what "nature" means, but she is quite sure it's on her side.

And, saving the best example for last: Last August, the Roman Catholic bureaucracy launched a global campaign against gay marriage as a "violation of natural law." Catholic teaching says homosexuality, birth control and divorce are all "unnatural."

This campaign links back to the Inquisition, the office that burned heretics and Jews, tortured people and even opposed the solar system, all for being unnatural.

So I guess I should not be surprised if latter-day true believers have followed tradition. It still works: Appeal to nature, call something unnatural and you seem to have won the argument, even though what it means is tangled in contradiction. A little humility, please: We don't know yet, to any certainty, what nature is, so there’s no need to bash somebody over the head with it. Let's calm down, look around attentively, and get on with living in it.

David Oates is a contributor to Writers on the Range, a service of High Country News (hcn.org). He lives in Portland, Oregon, and is the author of Paradise Wild: Reimagining American Nature.