Maybe you were just saying how we needed our government to be something less than corrupt, or how women need to be safe in our society, or how evidence and logic should trump nonsense and prevarication, or how arguing about scientific realities is preventing us from dealing with them. And the person you were speaking with replied, with a touch of condescension, a hint of derision, and a little eye roll: “You have to live in the real world.”

Now, it really doesn’t bother me where people choose to focus their time and efforts. If they believe in a just cause, and they can maintain the effort for that cause, more power to them. If they don’t have time for what I think is most important, that’s fine, too—people can and must choose where to put their time, and it cannot be everywhere. But this is a special kind of righteous dismissal, and it isn’t what it sounds like.

When someone says, “You have to live in the real world,” they think they are saying that your suggestions are implausible, or foolish, or unachievable. They think they are gently steering you away from wasting your poor misguided energy on something that you, poor naïve soul that you are, do not realize is worthless.

But that isn’t what they really mean. What they mean is: “My version of the real world, the version I have created in my head, accepts these things as givens. So shut up about them already.” And maybe they mean: “…because changing them is too hard.”

Mostly they mean: “Stop making me question my assumptions.”

Now, there are reasonable ways to disagree with people. If one person is talking about systemic inequalities that disadvantage the poor and how we need more support structures, and another person is suggesting that the poor are leeching off the government safety net like the parasites they are, there is clearly grounds for disagreement. There is also room for both sides to support their arguments, and to reconsider their own assumptions. And even though I find one of those views offensive, that’s the place I would rather be in a discussion. Debating issues with people when I disagree with them helps me learn how their views differ, how to support my own, and where I am wrong.

But if either person says to the other “You have to live in the real world,” that room for discussion is lost. Instead of being a point of discussion, the issue has become a point of judgment. That is the signal to me that the other party in the debate doesn’t care about finding the truth of an idea, only about preserving their own worldview.

What’s worse, this phrase doesn’t just come up with people I radically disagree with—in its most painful, useless, divisive form, it is coming from people who I would like to have as allies. It can appear in even apparently friendly discussions, but its true meaning remains. “You have to live in the real world here. Wind power isn’t the answer; solar is the only workable choice.” And maybe: “The government is never going to be effective, so less of it will always be the better option. You have to live in the real world.” Or perhaps: “Of course men shouldn’t rape women, but you have to live in the real world—how you dress is going to matter.”

I can’t make people stop saying this. Neither can you. I can’t even avoid being frustrated every time I hear it. But we can keep the true meaning in mind. If we hear others saying it, we can translate and regroup—okay, what assumption are they guarding here? And, if we find ourselves thinking this about someone else, we can use it as a reminder to question our own assumptions.

Because, in the real world, people are going to say this, and think it, and not always know what they really mean. But in the real world, some of us believe in trying to build a better one.