To assume the very position at issue in an argument against an opponent is to beg the question against that opponent.

If we were to read the former, weaker sense of the possibility of motivation into this second premise, we get the claim that a rational, or perhaps virtuous, version of the agent would only be motivated to act in some way if the actual agent has some actual desire that could produce that motivation. This premise would be false if agents could be irrational or vicious precisely because they lack certain desires, a common view we discussed in section 1.3. Suppose we try instead to understand the f