Argumentum ad crumenam

Argumentum ad crumenam (argument to the purse) is the logical fallacy of concluding that an assertion is correct because the person making it is rich.

Examples

 * "If you're so smart, why aren't you rich?" It is possible to be both smart and poor.
 * "Warren Buffett has made a fortune off of the market, and he says that this recession will last a long time."

Discussion
In an ideal world, a person who knows a particular field well would be able to parlay this expertise into material wealth. And to some extent, this is true: a good electrician will likely make a better living than an incompetent one. To this extent, it may be possible to use wealth as a proxy for competence.

However, a person who is successful in one field may not be an expert in another. Even granting the rule of thumb above, we should not assume that someone who has made a fortune in electronics knows anything about medicine.

In addition, as with the argument from authority, it is a mistake to think that because a person is correct most of the time, that they are always right. Even smart and well-informed people can be wrong.

External link

 * Argumentum ad crumenam at philosophicalsociety.org