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05/11/2011

false cause

Filed under: Logic — anlactunay @ 9:59 PM

false cause
Improperly concluding that one thing is a cause of another. The Fallacy of Non Causa Pro Causa is another name for this fallacy. Its four principal kinds are the Post Hoc Fallacy, the Fallacy of Cum Hoc, Ergo Propter Hoc, the Regression Fallacy, and the Fallacy of Reversing Causation.
Example:
My psychic adviser says to expect bad things when Mars is aligned with Jupiter. Tomorrow Mars will be aligned with Jupiter. So, if a dog were to bite me tomorrow, it would be because of the alignment of Mars with Jupiter.
Post Hoc
Suppose we notice that an event of kind A is followed in time by an event of kind B, and then hastily leap to the conclusion that A caused B. If so, we commit the post hoc fallacy. Correlations are often good evidence of causal connection, so the fallacy occurs only when the leap to the causal conclusion is done “hastily.” The Latin term for the fallacy is post hoc, ergo propter hoc (“After this, therefore because of this”). It is a kind of false cause fallacy.
Example:
I ate in that Ethiopian restaurant three days ago and now I’ve just gotten food poisoning. The only other time I’ve eaten in an Ethiopian restaurant I also got food poisoning, but that time I got sick a week later. My eating in those kinds of restaurants is causing my food poisoning.
Your background knowledge should tell you this is unlikely because the effects of food poisoning are felt soon after the food is eaten. Before believing your illness was caused by eating in an Ethiopian restaurant, you’d need to rule out other possibilities, such as your illness being caused by what you ate a few hours before the onset of the illness.
Cum Hoc, Ergo Propter Hoc
Latin for “with this, therefore because of this.” This is a false cause fallacy that doesn’t depend on time order (as does the post hoc fallacy), but on any other chance correlation of the supposed cause being in the presence of the supposed effect.
Example:
Gypsies live near our low-yield cornfields. So, gypsies are causing the low yield.
Regression
This fallacy occurs when regression to the mean is mistaken for a sign of a causal connection. Also called the Regressive Fallacy. It is a kind of false cause fallacy.
Example:
You are investigating the average heights of groups of Americans. You sample some people from Chicago and determine their average height. You have the figure for the mean height of Americans and notice that your Chicagoans have an average height that differs from this mean. Your second sample of the same size is from people from Miami. When you find that this group’s average height is closer to the American mean height [as it is very likely to be due to common statistical regression to the mean], you falsely conclude that there must be something causing Miamians rather than Chicagoans be more like the average American.
There is most probably nothing causing Miamians to be more like the average American; but rather what is happening is that averages are regressing to the mean.
Reversing Causation
Drawing an improper conclusion about causation due to a causal assumption that reverses cause and effect. A kind of false cause fallacy.
Example:
All the corporate officers of Miami Electronics and Power have big boats. If you’re ever going to become an officer of MEP, you’d better get a bigger boat.
The false assumption here is that having a big boat helps cause you to be an officer in MEP, whereas the reverse is true. Being an officer causes you to have the high income that enables you to purchase a big boat.
http://www.iep.utm.edu/fallacy/

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