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“”The truth may be puzzling. It may take some work to grapple with. It may be counter-intuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true.
Common sense is something which you think you know to be true but that may not actually be true. It is a way of reasoning based on immediate knowledge gathered about the world, and basic rationality applied to that knowledge. However, the danger with common sense is that the scope of knowledge can be quite wrong, and the basic rationality can simply not be deep enough for an attempt at finding truth. For something that is supposed to be common, however, sometimes it would seem like it should be called rare sense.
 The uncommon nonsense
For all practical purposes, "common sense" is a body of "rules-of-thumb" for how the world operates, which may or may not be shared with others in the community. For the most part, this works fine; for instance it is common sense not to walk in front of a speeding car, since, at some point in your past, you've seen fast things hit fleshy things and said to yourself, "ouch". Common sense would also suggest that a small person might best avoid antagonizing a large person as he can easily imagine the effects of flying fists. Common sense is not taking the time to mentally calculate the effects of the car's momentum being transferred to your own body, how far the impact will push you, or any other higher end science based function. Get out of the damn way, cause that's bound to hurt! will suffice. This is all part of our survival mechanisms to make it more likely we live on to reproduce.
It's not entirely impossible for people to have their common sense overridden by logical deduction if it's explained properly. While most people get the Wason card problem or the Monty Hall problem completely wrong because their common sense (that is, the inferences that we develop over time) comes to incorrect conclusions, pretty much everyone accepts the right solution when it's described to them.
The lesson: if something doesn't seem right even if "common sense" says it should be, it's time to get your science on.
 Science and common sense
“”[Common sense] that layer of prejudices laid down in the mind prior to the age of eighteen...
Common sense plays a role in science. If there are two possibilities that could both be true, it is accepted by science that the most simple, most "common sense" answer is the place to start, and until or unless it is disproved or "wobbly," it should be given more weight than an answer that breaks common sense until more evidence can be gathered. Mostly this is settled by Occam's Razor, in which case the preferred answer is the one that requires the fewest assumptions.
|“||Common sense is nothing more than a deposit of prejudices laid down by the mind before you reach eighteen.||”|
Often, many physical laws that are true defy common sense. Quantum mechanics is full of this sort of thing. How, exactly, does an electron need to turn through 720 degrees to come back to where it started‽ Or how can an electron pass through a node in the wavefunction if it can never actually be at said node in the first place‽ The fact that the evidence defies such common sense is in fact a massive barrier to people trying to fully understand quantum theory — and numerous interpretations have been produced to try and make it less nonsensical.
But you don't need to go into exotic theories that were only developed once technology had grown to the point where we could detect it. For example, it is common sense that if you drop a ball, it will fall. It always has, and it always will. It is common sense that the sun came up yesterday and will tomorrow. What is not such common sense is that gravity is a force (maybe) or an interaction between the ball and the Earth causing the ball to be drawn down to the earth, and the earth to in fact be drawn up, theoretically. Common sense would in fact deny that possibility, though it is the more true one. Common sense would also tell us that heavier objects drop faster than light ones — but this is actually an illusion caused by air resistance as was proven by science and then aptly demonstrated on the moon centuries later. In fact, the inferences we make about such objects can bleed into otherwise obvious questions, such as asking which is heavier, a ton of bricks or a ton of feathers — people might instinctively think of the bricks before having that "wait a sec!" moment.
 So if it's wrong, what's the point?
Common sense allows us to function in the every day world. Common sense tells us that the sun came up yesterday and will tomorrow, so we do not have to go to bed in fear. Common sense tells us that eating too much will make us sick (since it has in the past), and that red glowing things tend to be hot, and red signs tend to indicate danger. It is our very survival mechanism at work, even when it lies to us.
Common sense is in fact, our very entry into being a thinking thing. "Does this new idea I have, fit into the everyday world as I know it, and if not, why not".
|“||Common sense is not what the mind cleared of cant spontaneously apprehends; it is what the mind filled with presuppositions...concludes.||”|
Common sense is often confused with rational thought, being that people often believe common sense must be true and act incredulously to rational or scientific ideals that contradict common sense. This is due to the fact that the human brain can easily work with ideas like "common sense" and "rules of thumb" but can't quite cope with physics and statistics. For instance, it is statistically more probable to die from an asteroid impact (a rare and implausible event to many people) than a lightning strike (a common and very plausible event, particularly to golfers). Common sense is often made up of much prejudice and snap judgement, and therefore is not always useful and can certainly be irrational even when it is useful.
A similar train of thought is used by religious fundamentalists who insist that while other religious groups may have their own, incorrect, "interpretation" of holy scripture, their own group does not have an "interpretation" at all. They, you see, simply read the plain and direct words of scripture, whose meaning is clear to anybody with common sense.
Oh, and if you want to use it as an adjective, then the word is commonsense.
 See also
- Cognitive bias
- Common Sense was also the name of a pamphlet by Thomas Paine that was highly influential during the time of the American Revolution.
- Cracked.com: "5 Ways 'Common Sense' Lies To You Everyday."
- ↑ http://www.positiveatheism.org/writ/saganws.htm
- ↑ Wobbly, you say? According to Krauss, that's a perfect term to describe theories that are being pushed to their possible limits
- ↑ Einstein Wikiquote
- ↑ Feather & Hammer Drop on Moon
- ↑ Clifford Geertz. Common Sense as a Cultural System. In The Interpretation of Cultures
- ↑ Probabilities of dying
- ↑ Which English? (2010 archive)
- ↑ http://www.gutenberg.org/etext/3755