What is common sense?

[loinburger]

Common sense is knowledge that you'd die without (or that your children would die without), e.g. the "without food you'll die" example. The gray area is the knowledge that might not immediately kill you, e.g. the "without vaccines you'll die" example - I'd call this common sense, but I won't be proven to be correct until everybody who disagrees with me dies of measles (or they won't be proven correct until I die of autism).

If a piece of information doesn't have life-or-death consequences then I wouldn't say that it falls under the category of common sense - for example I'm firmly of the opinion that evolution is a superior theory to creationism, but I wouldn't say that a creationist is lacking common sense since their beliefs aren't lethal.

[Lorizael]

Hmm. If an asteroid is heading for Earth and your only chance of survival is a spaceship heading for Mars, is it common sense to get on the spaceship? Most people don't have direct means (until it's way, way too late) of being confident that an asteroid is going to strike the Earth or that a spaceship heading to Mars is going to work/isn't some kind of trick/etc.

[loinburger]

IMO "common sense" doesn't come into play here because personal values come into play too much - I'd understand somebody who wants to get on the spaceship, as well as somebody who says "**** it, I'm not living the rest of my life eking out an existence on an irradiated wasteland" and instead spends their life savings on hookers and blow before the asteroid hits. The same goes for somebody with late stage cancer - I'd understand somebody who opts for chemo/surgery (with a low probability of success) as well as somebody who opts to enter a hospice for pain management instead. "Common sense" means that you don't want to die and take actions to help ensure your survival - if you're at the point where death is a viable choice then "common sense" goes right out the window.

[loinburger]

I guess that more generally I'd say that "common sense" means that your actions are consistent with your beliefs/goals/desires, with "wanting to live" / "wanting your offspring to live" being a fairly common goal/desire (however, this isn't always going to be the case). For example, my high school football coach often said that one of my teammates lacked common sense because he often ran the wrong way down the football field, and this was inconsistent with the goal of scoring a touchdown (whereas my teammate would argue that he had common sense because running the wrong way down the football field was a good way to avoid getting hit by the other team, this being a more important goal to him than scoring a touchdown)

[Lorizael]

Well, then what's the difference between common sense and rationality?

[loinburger]

I can't think of a time when I've said that somebody lacks common sense where I couldn't have instead said that they're being irrational - I think the two concepts are interchangeable. If somebody has goofy-ass beliefs that are counter to their goals (in my opinion), e.g. if somebody has the goal of having healthy offspring but is also an anti-vaxxer, then I'd say that they're being foolish/gullible as opposed to saying that they're lacking common sense - I'd say that their actions are consistent with their beliefs and that therefore they're displaying common sense, but that their beliefs are wrong. (This is assuming that their anti-vaxxer beliefs are consistent - if somebody says "Jenny McCarthy is dumb as a pile of rocks AND I believe everything she says about vaccinations" then I'd say that they're lacking common sense)

[Lorizael]

I think common sense could only be a subset of rationality in that conception. Like, rationality has a lot to say about whether you should betray your crime partner or if you should switch to a different door after a prize has been revealed, but you're rarely going to call any of that common sense.