A refresher in logic
Logic is a funny thing. We all seem to think we’re logical creatures but we very often act in ways that don’t seem very logical. Maybe this is because relatively few people know even the basics of logic–we seem to confound “logic” with “intelligent” or “good decision making”. In fact, logic is a well structured discipline just like algebra or calculus.
The basic rules of logic are easy enough to follow:
If P, then Q.
P is true.
Therefore, Q is true.
Without any formal logic training, we can all follow the above example. But most of us quickly get tripped up by negation.
If P, then Q.
P is not true.
Therefore, Q is not true.
The above example appears to follow the same rules as before, but in fact it is wrong. This is easily the most common logical fallacy. Negating P tells us nothing about Q. The correct way to use negation is below.
If P, then Q.
Q is not true.
Therefore, P is not true.
A crucial distinction! But what’s the point?
Let’s apply the rules of logic to our ongoing discussion of what to do with the Big-3 auto companies.
If (massive government loans) then (no bankruptcy)
No massive government loans are made
Therefore bankruptcy
Ah ha! We’ve again fallen for the logical fallacy. Negating P (in this case the massive government loans) does not infer that we must negate Q (bankruptcy).
Of course, in the real world (and certainly in the world of politics) formal logic may not always work. People and economic systems are not always rational and are certainly not logical. None the less, it’s worth while to stop and consider the reasoning that the politicians, corporate executives, and cable news talking-heads are using when they fortell the future.
I don’t think they’re using logic.
Filed under culture, economics : Comments (1) : Dec 13th, 2008 by tadfad
May 18th, 2009 at 09:19
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