Non Causa Pro Causa


The argument offers an explanation that confuses correlation with causality. One thing is cited as the cause of another, but, while there may actually be a connection between the two, the hypothesis mis-locates it, either making the effect into the cause, or treating as cause and effect two things that are each results of a common cause.



The phrase "non causa pro causa" is a Latin phrase that means "not the cause for the cause," i.e. that one has confused what is not the cause for the cause. The fallacy is generally referred to by the shorter phrase "non causa."



"Putting more police on the streets actually causes crime to increase! When we increased the number of cops on the beat, the number of crimes witnessed by police actually went up."


"On a South Pacific island, where lice are common, we noticed that sick people tended to have fewer lice than healthy people. We conclude that having lice actually promotes health."


"People on Medicaid tend to be sicker than people who do not have insurance at all. This proves that Medicaid is a bad idea. Putting people on Medicaid actually causes them to get sick." 



Aristotle thought of cause and effect as simultaneous: a cart moves at the same time that the horse pulls it. The very moment that the horse stops pulling, the cart stops moving. Hence, when we observe two events occuring together, it is reasonable to suppose that there is some causal relation between them. (Of course, Retroductive reasoning can be based on concomitances other than temporal simultaneity. Cause and effect must also be of about the same "size." A horse and a cart are roughly the same size. It would be peculiar to see a cart drawn by a flea, or, for that matter, a jumbo jet.)

The fallacy of Non Causa Pro Causa generally begins with the observation that two events appear to be related by some concomitance or other (usually simultaneity of time). As such, it appears to be a good piece of Retroductive reasoning, since this is how any piece of retroductive reasoning must begin. Unfortunately, concomitance is a symmetrical relation. If A has something in common with B, then B has something in common with A. Hence, even if there is a causal relation between things, it is often hard to tell which is cause and which is effect. Good Retroductive reasoning must also be guided by some common sense regarding how causality works. The Non Causa fallacy is Retroductive reasoning without the common sense. For example, we know that horses are animate, i.e. that they are capable of self-initiated motion. Hence, when we see a horse and cart moving together, we naturally attribute the movement of the cart to the movement of the horse, not the other way around. The Non Causa fallacy puts the cart before the horse. In the above example, lice prefer to feed on healthy people; hence, having lice is the effect, not the cause, of being healthy.


Source: Aristotle, Sophistical Refutations 5 (167b: 20 -35).


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