I’ve been noticing a commonality in a lot of conversations I’ve had with people from both the right and the left.  One of the main reasons they refuse to support voluntary interaction over government mandate for a given problem is this:

“Yeah, you’re ideas sound great, but you’ve got to understand that most people don’t have common sense.”

It’s very similar to the clichés of “most people are stupid” and “there are a whole lot of dumb people in the world.”  I’m not sure that most people really mean it when they say these things—after all, it’s quite the condescending position to take since it implies that the speaker finds himself to be significantly smarter than most people in the world.  So while I don’t like those kinds of comments, I can give a lot of people the benefit of the doubt and assume they’re saying it in jest.

But when it’s one of the main points of your argument, then that’s a different story.  A recent example of this was in a conversation about (you guessed it) the roads.  It must be self-gratifying to be able to recognize all of the stupidity of the people among you: “Oh, you and I could get along fine without the micromanagement of the government, but it’s all of the other people who would be lost without it.  I’m just being considerate of their mental shortcomings.  I’m so very charitable that way.”

The idea, however, that most people don’t have common sense is actually itself devoid of common sense and demonstrates a lack of basic critical thinking skills.  Here is how Wikipedia defines common sense:

Common sense is a basic ability to perceive, understand, and judge things, which is shared by (“common to”) nearly all people and can reasonably be expected of nearly all people without any need for debate.

Do you see how silly it is to say that most people don’t have common sense?  It is a contradiction of its own basic definition.  It’s like saying that water isn’t wet.

The argument is therefore completely fallacious and should be identified as such.  The person who uses it could have either miss-qualified something as “common sense” or is one of few who does not fall into the category of “nearly all people.”  On the other hand—and this is probably the most likely reason—the person has no better response to your argument.