  The non-naturalist could simply deny the practicality requirement on moral judgement (this would be similar to the first reply to Mackie’s objection). This is considerably more controversial than denying the very strong link between motivation and moral judgement presupposed by Mackie’s objection, but may nonetheless be defensible. The idea would be that an agent can judge that she is morally required to do something and not be motivated accordingly without being guilty of any kind of irrationality. One might hold this on the grounds that the belief that one is morally required to do something does not commit one to the belief that there is conclusive reason to do it or on the grounds that the belief that there is conclusive reason for one to do something simply does not commit one to being motivated to do it on pain of irrationality. Unfortunately, a full discussion of the issues surrounding the truth of the practicality requirement on moral judgement goes beyond the present scope. For useful discussion, see Brink 1986, Foot 1972 and Smith 1994.