How does the fallacy of the undistributed middle (FUM) arise in economics?

FUM can be exemplified as: The queen has a poodle; I have a poodle; I am queen.

This can be rewritten as: If I am queen, I have a poodle; since indeed I have a poodle, then I am queen.

FUM then boils down to hypothesizing that P implies Q, and then claiming that P is true because Q is true.

This restates what we ought to know from logic – that FUM is a formal (syllogistic) error. This error, when expressed in terms of P and Q, is that of not ruling out all the other possibilities that can produce Q.

In economics, we can think of P as the unseen but ‘true’ model, which has an implication Q. If we gather statistics to show that Q is true, can we proclaim hallelujah that P is true? No, because this would be exactly just another FUM! And yet we find that this thought process using FUM underlies many an article in economics journals (to EC 23 students: gentle reminder that this is a HW assignment).

Karl Popper would now stir from his grave, and say that humans never learn. (Does that mean that Karl was at least part alien?)

FUM is no fun.

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