I’m coming to think more and more that the phrase ‘common sense’ is, or at least can be, quite a dangerous one.
In short, when it’s reasonable to apply it, it’s redundant, and when it’s not reasonable to apply it, it’s misleading. After all, if something really is common sense, then it should be evidently true to most people, and you don’t need to tell people that something obviously true is obviously true. But if you’re ever told that something is common sense and you’re not convinced that it is, then there are two possible reasons: you’re wrong, and you lack wisdom, or the term is being used misleadingly. And if it’s the latter, then the chance of being taken for a fool discourages you from challenging it (well, many people; some people don’t mind being taken for fools). It’s just common sense that the Emperor must be wearing clothes. Even worse, the term implies that we need look no further into the matter, and this discourages research. How many times have you heard scientific results dismissed with: ‘Well I could have told them that! That’s just common sense!’
But the term is not just dangerous when used misleadingly; if used for things that really are self-evidently true, then it’s not doing any good, as it’s redundant, and inasmuch as it provides a safe environment for the term’s misuse, then it’s actually harmful.
OK, so there may be some cases where the term can be used that do not fall into the categories above: how about where we don’t say that x or y is common sense, but we simply call for more common sense, by which we mean, I suppose, less extremism. Well, that’s OK, and the world would indeed be a better place with less extremism… except… except… one person’s extremism might in fact be another person’s common sense. It seems to me, for example, that opposing gay marriage is extremist and irrational (or at best rationally based on highly dubious premises). But to many other people, it’s simply common sense that marriage should be between a man and a woman. To others it is common sense that ‘Britain should be for the British!’ by which they mean that immigration is destroying us.
It’s a hard habit to get out of, this term, and I suspect that I’ll find cases in my life where it really does seem the best term to use, and it really does seem to be doing some useful work. But I’m going to try to avoid it all the same.