Preferences, Welfare, and Normative Economics

Welfare economists take welfare to be the satisfaction of preferences. Yet it is obvious that people sometimes make bad choices. (I certainly have.) People often prefer what is bad for them. It requires no philosophical acumen to recognize human fallibility. An uncharitable observer might conclude that economists are dunces. When defenders of cost-benefit analysis maintain that the “net benefit” of policies ought to influence public choices, they assume that what they call “net benefit” indicates preferences and that preferences indicate welfare. It seems there is a problem. Does welfare economics rest on a philosophical blunder?