Common sense is very useful, in fact essential, for checking the reasonableness of ideas or conclusions. However it can only ever be effective as a screening technique, not as a final determinant of what we believe. If we only believed what common sense supported we would never have had flight, electricity, steam power, space flight or the internet. Common sense should always be invoked as a challenge to new ideas, but only as an indicator of when we need to reinvestigate the reasoning behind the idea and the assumptions underlying it. If, no flaws are found in that reinvestigation, we should accept the new idea. As Sherlock Holmes said ‘when all other possibilities have been excluded, the remaining possibility, however improbable, must be the truth’. Or something like that.
So next time you hear someone claim that something can’t be true because it doesn’t agree with ‘common sense’, tell them that, if that’s the only argument they have, then they have no argument at all.
The value of common sense is that by causing you to reinvestigate reasoning and assumptions, it can lead you to find the true reason why a conclusion is not correct. If it doesn’t lead you to that then you need to update your idea of what constitutes common sense.
Shock jocks like Alan Jones love to appeal to common sense as their argument, whether it be that climate change doesn’t exist, that shifting the focus from prohibition to harm minimisation will increase drug use, or that lowering taxes will be good for the economy. Remember, valuable as common sense is, if that’s all you have then you have nothing.
A proper use of common sense is to say that if an idea isn’t consistent with historical observations and generalisations, then there’s a high probability that it’s wrong. An abuse of common sense is to say that the idea must be wrong. Most of humanity’s greatest advances have come from ideas that defied common sense. A society that insists on abusing common sense in this way will never make any new inventions or discoveries. It will wither and die.