Allow me to begin with a story. A fellow walks up to the dog-licensing clerk and demands a license for his cat. The clerk points out that there is no such thing as a cat license, and thus he has no need of a cat license. Noting the man’s confusion, she explains that dogs and cats are different kinds of animals. Dogs tend to wander off and get lost, dig up other people’s yards, bite people, get into garbage, and leave their droppings in inconvenient places; cats generally do not do these things. Licensing would be pointless, for the government doesn’t need the same control over cats as it does over dogs.

The customer feels unaffirmed in his choice of a cat, and demands that the government recognize that his cat is just as important as a dog. Oh, but it’s not a question of importance, the clerk insists; it’s just that cats and dogs are quite different, and there is no government interest in licensing cats. He pesters her for so long that, eventually, the clerk, in sheer frustration, grabs a form, crosses out the word “dog” and writes in the word “cat” in crayon. The customer goes away pleased.

Unexpectedly, some of the man’s cat-owning friends soon follow suit. This raises concern for the licensing administrators. They really cannot justify taking money to license cats, yet it seems many people are made quite happy by having their choices validated. Finally, it occurs to someone that, since dogs are four-legged furry mammals with tails and claws, and cats are four-legged furry mammals with tails and claws—and after all, this really is the only set of characteristics that matters—then the obvious thing to do is to redefine “dog” so that it includes cats.

This decision is not without its detractors. Some sticks-in-the-mud point out that the definition is so broad that it also includes bears, rabbits, gerbils, and ferrets, not to mention the incredibly obvious fact that cats simply are not dogs, and that redefining them does not change this fact, and that changing definitions based on policy preferences will only lead to problems. These arguments fall on deaf ears. The city council makes it official, redefining “dog” to include cats. Why cat owners feel affirmed by having their cats renamed “dogs” remains a mystery.

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Several more cities take up the call to rename cats “dogs,” but most towns resist because, as they point out, it’s simply not true that cats are dogs. The state legislature is besieged with efforts to rename cats as dogs. The state has always left policy choices about cats and dogs to local deliberations, but is now in an awkward position. It runs several venues that admit dogs but not cats; it has compensation policies that are differently affected by ownership of cats rather than dogs.

No state legislator or administrator has ever thought it necessary to define “dog,” since everyone knows what a dog is, and what a dog is has not changed in the entire history of humankind or caninekind. It is also plain as the nose on everyone’s face that dogs are not cats, and vice versa.

Failure to define the term, though, will only lead to confusion about employee compensation and mischief at state-run venues. The legislators recognize a simple fact: No matter how one defines “dog,” it cannot be the case that both definitions are true. Either “dog” will be defined according to its observable operations, or it will be defined according to its nonessential outward appearance. They decide to go ahead and define “dog” in the “traditional” way, according to the reality of dogs and cats, such that cats are excluded.

What is the reason for this story?

There is an argument afloat that the federal Defense of Marriage Act (DOMA) is, in George Will’s terms, “constitutionally improper.” Will’s argument is a decent stand-in for misguided federalist arguments against DOMA, so allow me to quote from his recent essay:

The question now is whether DOMA is “necessary and proper” for the exercise of a constitutionally enumerated congressional power. There is no such power pertaining to marriage. This subject is a state responsibility, a tradition established and validated by what can be called constitutional silence: The Tenth Amendment says, “the powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people.”

DOMA’s defenders claim that Congress simply officially defined a term used in over one thousand federal laws. But some federalists argue that before 1996, Washington did fine without such a definition, and that the real purpose of DOMA is to make a policy choice: to protect a traditional understanding of marriage instead of a new one.

It shouldn’t surprise us that, prior to DOMA, the federal government hadn’t officially defined marriage as between one man and one woman: No one would have found it necessary, because no one in his or her right mind would have thought it could possibly be something other than a vow between a man and a woman.

There are serious risks in adopting definitions based on wishful thinking, not reality. Here is an analogy. Some feminists claim that the laws of physics and chemistry are male constructs, and so posit a new set of laws. These laws are necessarily incompatible with the ones we have always known.

Now if a state were to adopt these new laws, would everyone else have to adopt them? Would the federal government, in laying out plans to build interstate highways and bridges, to formulate vaccines, or to fly airplanes, have to follow them? It’s hard to imagine why. Indeed, the federal government would seem to be shirking its most basic duties to the public without proof over a long time that these new laws were actually viable for scientific progress.

The push to redefine marriage is rooted both in human desire and prior policy choices. Given our penchant for liberty as license, we have chosen no-fault divorce and the complete separation of sexual acts from their natural end, children. Thus we now understand marriage in terms of its secondary, non-essential characteristics, like romantic love.

Sadly, we already know the consequence of these choices: marriages dissolved, families broken, children without both parents (or with lots of parents but no sense of filial loyalty), abortion, couples discovering that they are genetically related through sperm-donor fathers, and all the other social upheavals that follow in the wake of this mess like sharks at a shipwreck.

Since we have fifty years of sad experience with chaos caused by tinkering with how marriage is practiced, it would seem absolutely foolish to pretend we can change what marriage is without waiting quite a long time to see how the changes work in isolated local experiments.

But the deeper problem with the misguided federalist argument for striking down DOMA is that it conflates definitions with policy choices. A policy is an organization’s way of acting in relation to X. A definition is a claim about what X is. We don’t make policies about what X is; X is the given about which we make choices about how to act.

We can also put it this way: When we do make definitions a policy choice, or settle on definitions based on previous policy choices, nothing follows but mischief. When X is part of the nature of reality, like dogs and cats, altering definitions becomes an exercise in absurdity.

In our marriage debate, we aren’t dealing with a policy question. We’re dealing with a definition of the subject of our policies.

What’s at issue isn’t marriage and family law, or what sorts of arrangements we make concerning marriage and family. What’s at issue is the meaning of marriage itself, and consequently the meaning of family.

Marriage and family law have at their core, throughout history, a basic understanding of a universal fact: the sexual acts of man with woman result in children. For the sake of their offspring, they vow to each other and to the community to be sexually exclusive and remain together, blending their bodies, their goods, and their lives. Society supports them in their task. This is marriage.

Government does no more than recognize this fundamental fact of social life. Marriage comes to us already defined, and governments have typically tried to form policies that match the reality. It may well be that, from time to time and from place to place, there have been alterations in how this social arrangement plays out: which men may marry which women, how many spouses are permitted, how spouses and children inherit, how easily one may be released from the vow.

But never until the 1990s had anyone questioned what marriage is. Never before had anyone simply redefined the institution to be something else entirely, based on entirely non-essential characteristics. The new marriage regime is not about recognizing marriage; it is about validating people’s love interests. But society and its governing bodies have no more use for or an interest in granting a license for people’s loves and friendships than they have in licensing cat ownership.

The federal government has to have a definition of marriage, if for no other reason than that it has to compensate its employees, and some of that compensation may involve claims of marital status. There is absolutely no reason why the federal government should adopt as its definition the one being pushed by same-sex marriage proponents, a definition based not in the reality of human sexuality and human relationships, but in the wishes of powerful adults.

The federal government is no more required to do such a thing than to accept feminist laws of physics when flying over states that recognize them. Sure, those states can recognize the laws they prefer, but that doesn’t mean we—the federal government itself, and the remaining thirty-eight states participating in that federal government—have to go along. When there are mutually incompatible definitions, it is logically impossible to choose them both. Each governmental body is going to have to make a choice of one or the other.

But remember this: When we define our terms based on the results we want, rather than on the reality of the thing being defined, all hell breaks loose.