I want to start with a simple experiment, and I want the folks with the "No Borders, No Nations" stickers to play along.

Tonight, before you go to bed, unlock your front door. Leave it open a crack. Put a sign in the yard that says anybody who wants to come in is welcome, no questions asked, stay as long as you like, help yourself to the fridge.

You are not going to do that. I know you are not, and you know you are not. And that tells us something.

Here is what every homeowner in this country already understands. A door is not an act of hatred. A lock is not bigotry. You put them there because the house is yours, the people in it are your responsibility, and you get to decide who comes through. That is not cruelty. That is just what it means to have a home.

Now, I am not against company. I love company. My mama raised me to set an extra plate on Sunday and mean it. Most Americans are the same way about this country. We let roughly a million people become permanent residents in a typical recent year. That is a lot of extra plates. Nobody serious is talking about shutting the door for good.

The difference is the knock.

When somebody knocks and you let them in, that is hospitality. When somebody climbs in the back window while you are asleep, that is something else, even if they turn out to be a perfectly nice person once you get the lights on. The niceness of the guest does not change who was supposed to decide.

That is the whole argument, and it has nothing to do with where anybody is from. A family from Guatemala and a family from Germany ought to get the exact same answer: knock, and we will talk.

The no-borders folks like to say a country is not a house, and I want to give that its due, because it is the best thing they have got. They are right that America has no single owner. They are right that a lot of the people who come here were invited by somebody: an employer who needed workers, a relative who sponsored them, a church that took them in. And they are right that my little metaphor does not tell you how many people to let in or who.

Fair enough. But notice what that argument concedes. It is an argument about who gets to answer the door, and how many plates we set. It is not an argument for taking the door off the hinges. The minute you start arguing about who the household is and how it decides, you have admitted there is a household and there is a door.

And the household, in a country like ours, is the voters. We pick the folks who write the rules about who comes in. You can lobby them to let in more people. You can lobby them to let in fewer. That is a real debate, and good people land on both sides of it.

What you cannot do, at least not with a straight face, is tell me the door should not exist while you are sleeping behind a deadbolt.

So here is my offer. The day I drive past your house and see the door wide open and the sign in the yard, I will sit down and take your argument seriously.

Until then, I am going to assume you understand doors just fine.