My compatriots may remember the Mike Harris government in Ontario during the 1990s. It can best be thought of as a sort of dry, trial-run for our present Mr. Harper (and indeed it even uses quite a few of the very same cabinet ministers). Hard right wing ideology was the law of the day, and it was all justified under the slogan of “Common Sense.” Ever since then, I have been reflexively suspicious of anyone who uses this term, and frankly, if you ever find yourself trying to justify your beliefs by referring to common sense, then I strongly urge you to punch yourself in the mouth as hard as possible.
People like to say that the problem with common sense is that it is not actually very common, but to me that seems to be more or less the opposite of the truth. I would argue, rather, that the problem with common sense is precisely that it is common. That is to say that there are “levels” of knowledge: the depth of your knowledge of any given subject increases with the amount of time you spend looking at it. By necessity, though, people can’t really look beyond surface-level understandings of the overwhelming majority of subjects in the world. And it precisely these surface-level understandings–and the reasoning based upon these understandings–which, by definition, constitute common sense.
For many purposes, this depth of understanding is sufficient. For example, a “common sense” understanding of physics is basically Aristotelian, but for the overwhelming majority of people even here in the twenty-first century it makes not one lick of difference whether the Sun orbits the Earth or vice versa, so long as the Sun still rises in the morning. But if you tried to apply common sense understandings to actual problems in physics, you would end up failing badly. The same applies in any other subject, I’m sure. My common sense understanding of music is that it’s just a bunch of repeating sounds in an aesthetically-pleasing combination, but I wouldn’t say that that qualifies me for membership in a band.
So I urge you to remember then, that if anyone–particularly a politician, as they seem inordinately fond of this– ever tries to justify their actions to you using the mantra of ‘common sense,’ they are essentially telling you–in so many words–not to think too deeply about it. Beware.