That people don't know what will make them happy does not invalidate what I said. They could well have desires they are not fully aware of, or are not aware of their current strength.

If you say that happiness comes from fulfilling desires, and that we can be unaware of your desires (or their strength), how can we measure those desires or their strength? Is it simply a matter of getting you drunk and asking? Making you take an implicit attitudes test? If we can only measure a desire by the happiness its fulfillment brings you, you have just set up a circular argument.

FAWS' lottery example is a good one. By any reasonable account of desires, most lottery winners strongly desire to win the lottery, and then start spending the money on satisfying their other desires. Yet by several recent accounts of happiness, winning the lottery appears to correlate poorly (or even negatively) with happiness.