Like a lot of Net Geeks, I've been following the Texas court case in which a comics-store employee was convicted of selling an adult-comic to an adult (interesting commentary, with links, here). Like most, I'm annoyed at the clear entrapment here, and I'm also dismayed that the prosecuting attorney based his entire argument on comics being primarily a children's medium. But what really got my goat was in his actual phrasing:
"Comic books, and I don't care what type of evidence or what type of testimony is out there, use your rationality, use your common sense. Comic books, traditionally what we think of, are for kids."
This angered me because I have come to absolutely detest the phrase "common sense".
First, I hate the phrase because it's totally nebulous. What constitutes "common sense" for one person is a lightning bolt of revelation for another. It's just common sense that you don't wear white after Labor Day. It's just common sense that you have your oil changed every three thousand miles. It's just common sense that you lather, rinse and repeat.
I suspect we all know people - - maybe from work, maybe from school - - who are near-savants when it comes to the books: they get good grades in tough subjects as easily as they breathe, the mere idea of them ever getting anything less than an A is unthinkable. But they are totally clueless in interpersonal relationships, perhaps; or maybe when you accompany them into a subway station they suddenly get that "caught in the headlights" look; or they lack any semblance of tact at all. We often say of these people, "Wow, they're sure smart, but they have no common sense". In that context, the phrase seems innocuous, simply describing knowledge that one really ought to have in order to function with others. But then, deciding just what constitutes that knowledge is a good deal more slippery than that. This is definitely the most harmless use of the phrase, but I still don't like it because it smacks of a kind of superiority: "Yeah, they smoke us on the grades, but we know how to order from the Soup Nazi."
Secondly, I hate it when politicians refer to "common sense". Democrats and Republicans both do it, and it makes me crazy to hear these guys talk about "common sense tort reform" or "common sense healthcare reform" or "common sense antiterrorism measures" or "common sense" anything. You know, when I'm trying to elect someone to lead this country or my state, or represent me in Congress, I don't want "common" sense. I'm looking for "uncommon" sense. I want someone who's smart as hell, and who can come up with solutions that in all likelihood aren't common-sensical at all. There was nothing "common sense" about the establishment of the United States Constitution, for example - - that took a convention of the smartest men (no women, sadly - - another way it took common sense a while to catch up) several months to hammer out a governmental structure such that no one was particularly enamored of the results. The United States exists because a bunch of people chose not to go with "common sense" in a time when "common sense" was that you followed your King and you liked it.
Of course, politicians aren't actually intending to use "common sense"; it's just a rhetorical tool, which leads me to my third and biggest reason for hating it: the phrase, like a lot of political catch-phrases ("We can't throw money at the problem" being another prime example), is actually intended to simply shut off debate. In my experience, one hundred percent of the time when someone invokes the phrase "common sense" in advocating a position, whether it's on something like educational policy or something so mundane as the fact that The Phantom Menace is a good movie, what they are really saying is: "My position is self-evident, and your disagreement with me is evidence of some deficiency on your part." It is meant not to argue, but to assert and put the opponent on the defensive. The prosecutor quoted above appeals to both "rationality" and "common sense", but note his use of "rationality": Ignore the evidence. Ignore all other testimony. I don't care what facts may exist that don't agree with me. This is "rational"? Last time I checked, "rationality" meant looking at the facts and testimony and then using reason to draw a conclusion; but that's not what this guy wants. He wants a predetermined conclusion, and anything that stands in opposition to that conclusion is, in his mind, to be completely ignored. Well, that's not "rational" at all, in the sense of using reason. People who appeal to "common sense" don't want you to use reason. What they want is for you to not think at all.
If you find yourself invoking "common sense" in a debate, the sad fact is this: you haven't done your homework, and you're conceding the logical ground to the other guy and resorting to brute force. Of course, it wouldn't be such a popular catchphrase if it didn't work a lot of the time. Just ask the poor comics dealer.