Comment: Absolutely wrong.

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Absolutely wrong.

Desire can be rational or irrational.

Desire for the next pizza may be perfectly rational. A desire for the 100th pizza within 24 hours would be LESS RATIONAL than the 99th pizza eaten within 24 hours.

You absolutely can measure ration of PERSONAL desire through utility. This is a basic tenet of free market economics.

In the primitive example I just provided, it is quite a MEASURABLY NEGATIVE MARGINAL UTILITY from eating your 100th pizza during a 24 hour period because you'll likely be dead afterward. However, eating that first pizza is POSITIVE because you require food to survive and you were hungry. The marginal utility of the 1st pizza eaten in the 24 hour period was POSITIVE and, hence, rational. The marginal utility of eating the 100th pizza in the same timeperiod was NEGATIVE and IRRATIONAL as it put you in the grave.

However, if you go purely off DESIRE, the DESIRE may have been constant for the 24 hour period. Did it make the desire rational? No. At the beginning it was rational, at the end the same desire was NOT rational.