Logic, thinking, and the named and unnamed logical fallacies.

Logic is a wonderful and necessary tool.   It is also desperately undervalued and misunderstood by way too many people, and occasionally rather abusively misused, which bothers me a great deal.

We all know about nonsense syllogisms, where you start with false assumptions and perfectly logically come to ridiculous conclusions. These make an appearance in pretty much every arena, however, with few people realising that the stated premises (on the given issue at the time) are false.  And, on a sort of a tangent, people are also very fond of saying things like “it’s only logical” about a conclusion they have reached, when what they really mean is “it makes sense to me because this fits perfectly with my preconceived biases and emotional investment in a certain worldview” — which is not the same thing as being logical, at all.

Real logic is a way of checking whether you are basing a conclusion on information which has been presented, or assumptions that you are supplying yourself. It is a way of fast-checking for internal inconsistencies which point to something being plainly incorrect. It is a necessary component of analysis, as well as lending itself to more rigorous thinking. Of course, in a culture with glorifies “feeling” as being the highest virtue and devalues rationality as something which somehow puts you out of touch with reality(!), a lot of people don’t appreciate this either. Which makes it easy for newspapers, snake-oil salesmen and politicians all to sell people on a lot of bullshit, frankly.

Feeling and instinct are exceptionally useful if that shadow in the bushes really IS a predator, and they are beyond a doubt important when considering things like, “do I really want to go on a date with this guy”, or “would I enjoy doing this for a living for years”; when it’s not an emergency avoidance of a predator, though, then we have room to think about things as well as just feel, and we should. I would just like to point out that the human brain generally makes up less than 3% of our mass, at most, but it takes about 25% of our body’s energy resources to run it. Evolutionarily speaking, we would not have developed this and we would not keep it if it didn’t give us an advantage; seems to me we ought to be using it.

So may I recommend, for all and sundry, a fast run-through of the most common logical fallacies. One of the best sites on the web for this is http://www.logicalfallacies.info/; it has a good run-down of everyone’s favourites from internet arguments. As an exercise, I would recommend going back over some of your own writing after reviewing these, as if you were disagreeing with yourself — make it a mental exercise of debate, play devil’s advocate against yourself — and seeing how many logical fallacies you, yourself have used that you didn’t spot or didn’t care about at the time, because you were making a case for something you were passionate about. (I try to do this on a regular basis. I would like to think it keeps me honest.)

As a follow-on from that, though, and perhaps on a slightly lighter note, I’ve spotted a couple of common failures of logic that I don’t know we necessarily have terms for. Can anyone enlighten me, do these have names yet?

  • “I don’t know, therefore no-one knows”, with the common variation of “I have never seen this information, therefore this information must not exist.” Based around the assumed impossibility that there is any knowledge out there that the speaker/writer doesn’t have.
  • “Since there are a lot of things that aren’t known about [x], nothing is known about [x].” It’s rarely stated as baldly as this, of course, but this is the general principle behind most arguments that [insert ludicrous statement about x here] could be true because science doesn’t know everything/has so many unanswered questions. The fallacy, of course, is in equating not knowing everything with not being able to eliminate anything, because even if we don’t know everything it’s generally safe to say we know some things. New “theories” must not only answer unanswered questions in order to have credibility, they must also fit with what we already know to be the case from observation.
  • …any others that people can think of?

This is my thought-exercise in favour of intelligence for today.


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