  To overcome these latter objections, the action-based theorist may follow any of a number of lines of argument. The action-based theorist may argue that mere beliefs in goodness cannot move agents to act, given an independently motivated theory of belief in general (a position open to many philosophers of mind with complementary theories of belief and desire). Or he may argue that there is an incoherence in the principles by which one should revise a belief in goodness and by which one should revise one's dispositions to act (see the discussion of Lewis below in section 1.3), so that there is something incoherent in the idea of a belief in goodness that also moves one to act. Or, in a more concessive spirit, he may allow that the action-based theory of desire should be supplemented with other elements (dispositions to pleasure, for instance) not characteristic of beliefs in goodness.