  The argument has other problems. One could deny that morality must be practical in the required sense. Perhaps morality need not be practical at all: we do not always withdraw moral judgments when we learn that the agent could not be motivated to follow them. Or perhaps moral judgments must be capable of motivating not just anyone, but only idealized versions of ourselves, free from (say) irrationality. In this case, it is insufficient to describe how we are motivated; what is relevant is a description of how we would be motivated were we rational.