I believe that the Desire-as-Belief Thesis is unacceptable as a way of unpacking the Broadly Anscombean View - namely, the claim that the good is the aim of desire in a sense analogous to how truth is the aim of belief - because of the following pair of asymmetries between desires and beliefs.
Beliefs are truth-assessable while desires are not. This asymmetry between desires and beliefs is reflected in our ordinary linguistic practice. For example, if I believe that George Washington was the first president of the United States, we ordinarily think of my belief as the sort of thing that could be true or false. By contrast, we do not ordinarily conceive of desires as truth-assessable. For example, if I desire to purchase a flat screen television, we do not ordinarily think of my desire as the sort of thing that could be true or false. Moreover, I believe the following theoretical account may be offered in defence of Truth-Value Asymmetry. First, I hold that a psychological state may be conceived of as truth-assessable just in case it represents the state of affairs that constitutes its intentional object to be the case or it represents a particular proposition to be true. Second, I take the preceding necessary and sufficient conditions to be met by the psychological state of belief. For example, if I believe that George Washington was the first president of the United States, I hold that the state of affairs of George Washington being the first president of the United States is the intentional object of my belief. Moreover, I hold that my belief represents this state of affairs as being the case. (Or, if one prefers, we may say that the belief that George Washington is the first president of the United States represents the proposition, “George Washington is the first president of the United States” to be true.) Third, I take the preceding necessary and sufficient conditions not to be met by the psychological state of desire. For example, if I desire to purchase a flat screen television, I take the state of affairs of purchasing a flat screen television to be the intentional object of my desire. Moreover, I hold that my desire does not represent my purchasing a flat screen television to be the case. The upshot of the three preceding theoretical commitments is that the psychological state of belief is truth-assessable, while the psychological state of desire is not.
One is guilty of irrationality if one knowingly has inconsistent beliefs, but one is not guilty of irrationality if one knowingly has inconsistent desires. This asymmetry is also reflected in how we ordinarily talk and think about desires. According to the present objection, one may have conflicting desires—for example, the desire to have a cigarette, and the desire to stick to one's New Year's resolution to quit smoking (where one recognises that these represent mutually exclusive desires)—without being guilty of irrationality. However, the same is not true of belief. If one believes that it is good to stick to one's New Year's resolution to quit smoking, and one also believes that is good to have a cigarette (where one recognises that these represent mutually exclusive beliefs), then one is guilty of irrationality. Moreover, I believe the following theoretical motivation may be offered in support of Rational-Commitment Asymmetry. First, I hold that beliefs are commitment-involving psychological states. For example, to believe that smoking is good is to be committed to holding that smoking is good. Second, I hold that desires are not commitment-involving psychological states. For example, to desire to have a cigarette is not to be committed to having a cigarette, since one may have such a desire and yet decide not to act on it. Moreover, one may desire to have a cigarette without being committed to the goodness of having a cigarette. Third, I hold that one is only rationally assessable for having a psychological state if it is commitment-involving. The upshot is that one is rationally assessable for having beliefs one recognises to be inconsistent, but one is not rationally assessable for having desires that one recognises to be inconsistent.
In summary, I reject the Desire-as-Belief Thesis because it overlooks two important asymmetries between desire and belief; Truth-Value Asymmetry and Rational-Commitment Asymmetry.