Sometimes, when trying to win an argument, a person might invoke the old “but it is surely just common sense that X is X or Y is Y”. And let’s face it, we all do it a lot of the time. Trouble is, this can lead us astray on difficult moral issues, for example, or in science, where “common sense” once led people of high intelligence to scoff at the notion of gravity, or that the earth was a sphere, etc. For all I know, people once thought it was “common sense” to have absolute rulers, burn witches, keep slaves and shun those of other races.
This comment in the EconLog thread, by RPLong, caught my eye:
Common sense is one of those fuzzy concepts that people invoke to buttress their arguments without providing additional facts or reasoning. I consider appeals to common sense to be a lot like saying “very, very, very…” That is, appealing to common sense provides more verbiage without providing any additional substance. It’s a waste of time. Unless we can actually show with facts and reasoning that our position is the more sensible, there is no use discussing that which appears most “commonly” to be sensible. If you have the more convincing position, then you can certainly demonstrate how much more convincing it is.
That’s surely the crux of the matter. It is one thing to say that “My opinion about the wrongness or rightness about abortion or the proper teaching of kids is just, you know, common sense.” But as soon as you start to break down the issues, look a premises, unacknowledged philosophical/other assumptions, it gets much more complicated. In some cases, an appeal to “common sense” is just an argument from authority.