In his Second Inaugural Address, President Obama declared that “if we are truly created equal, then surely the love we commit to one another must be equal as well.” Headlines and blogs around the country proclaim that the Supreme Court is ready to tackle the issue of “marriage equality.” If that’s the issue—“marriage equality”—then the correct outcome seems irresistible, doesn’t it? But is “marriage equality” really the issue?

In a recent exchange at the University of San Diego, a public interest lawyer told me that his organization was litigating in behalf of “marriage equality.” “So, if I’m opposed to same-sex marriage,” I asked, “I suppose I must be either against marriage or against equality?”

He grinned. “You might be against both.”

It was a clever response—but also a misguided one. And utterly question-begging, in an all too familiar and unfortunate way.

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To see how, think for a moment about the meaning—and the rhetorical uses and abuses—of equality and inequality. Do we treat blind people unequally by denying them drivers’ licenses when others are permitted to drive? Do we treat convicted felons unequally by putting them in jail when other people are free to move about as they wish? In the purely descriptive sense of different treatment, inequality is ubiquitous. Thank goodness. But we have something different in mind, obviously, when we talk about equality and inequality in political contexts.

Here, as Aristotle long ago observed and as Michigan law professor Peter Westen explained some years ago in a much-discussed article in the Harvard Law Review, equality has a more normative sense. It means that like cases (or, as lawyers say, “similarly situated” instances, or similarly situated classes of people) should be treated alike.

But in that normative sense, equality is wholly uncontroversial—and entirely useless. Everyone favors equality: Everyone thinks that like cases should be treated alike. Nobody argues, “These groups are alike in all relevant respects, but they should be treated differently.” So when people disagree about legal or political issues, they aren’t arguing for and against equality. Instead, they are disagreeing about whether two cases, or two classes of people, actually are alike for the purposes of whatever is being discussed.

With respect to that sort of disagreement, though, no answers can be squeezed out of the idea of equality, as Westen’s article explained. Instead, we have to refer to our political philosophies or our moral views or something of that sort. Something more substantive than the unassailable but substantively empty proposition that “like cases should be treated alike.”

Consider an example. We would treat blind people differently either by denying them the right to vote or by denying them drivers’ licenses. But we would treat them unequally only in the first case, not in the second. That is because an ability to see is not a relevant qualification for voting, but it is a relevant qualification for driving. We know this, though, not by applying the idea of “equality,” but rather by thinking about the nature of voting and of driving. Probably there is no disagreement about these particular conclusions. But if you did happen to encounter a good-faith disagreement, you would not be saying anything helpful if you thumped the table and declared that “blind people should be treated equally.” You would only be begging the question.

On this logic, Westen suggested that invoking equality is never helpful in addressing genuine disagreements about justice or policy. Hence his title: “The Empty Idea of Equality.”

Even so, the rhetorical power of “equality” arguments is plain enough. An advocate who frames arguments in terms of “equality” can get rhetorical mileage out of the descriptive sense of inequality—after all, people are being treated differently—and even more rhetorical mileage out of the irresistible injunction to “Treat like cases alike!” Meanwhile, the real substantive disagreements are kept mostly out of sight. Concealing the hard questions while free riding on truisms can be a powerful rhetorical strategy.

A purist (like Westen) might wish that the language of “equality” could be purged entirely from our legal and political debates, in the interest of promoting honest and responsible discussion of the matters we disagree about. That’s not about to happen, of course. Equality talk is in the Declaration of Independence, and the Gettysburg Address. And it’s strongly associated with noble causes, like ending slavery and dismantling Jim Crow segregation. (Which of course is still another reason why advocates like to frame their positions in “equality” language.)

And in some contexts the risks of equality talk are negligible. If someone advocates “racial equality” in employment, say, it’s clear enough what they’re saying—that race should not be considered in employment decisions. If someone favors “sexual equality” or “gender equality,” similarly, their meaning is pretty much conveyed by their language. There’s nothing especially veiled or sneaky here.

Which brings us back to “marriage equality.” Unlike the advocates of “racial equality” or “gender equality,” an advocate of “marriage equality” is clearly not saying that marriage is irrelevant for some purpose. Quite the contrary. In this respect, the advocate of “marriage equality” is no different from the proponent of traditional views of marriage: Both place a high value on marriage. Nor do the opposing sides differ about the imperative of equality: Both sides agree that “like cases should be treated alike.” Pretty much everyone, in short, is in favor of “marriage equality.”

So the real disagreement is not about equality, but rather about what marriage is, or what it should be thought to include. Among the vast spectrum of human relationships, many of them valuable or ennobling, which ones should be classified under the heading of “marriage”? On that question, there are various views. Some think marriage is a relationship between one man and one woman. Some think it can include relationships between two committed adults, regardless of sex. Some would not limit marriage to only two persons. Some would not limit it to adults.

Reasonable people can debate these views in good faith and in various vocabularies—cultural, psychological, political, theological. So there are important debates to be had, and important decisions to be made. But the debates will only be cluttered up, and the decisions confounded, if the issue is framed in the question-begging terms of “marriage equality.”