 The dualism of practical reason is precisely this fact, that practical reason is guided by two distinct but potentially incompatible rules. This incompatibility will not always rise to the surface, but there is a possibility that the two methods give divergent results. As Sidgwick writes, in such a case, “practical reason, being divided against itself, would cease to be a motive on either side”(508). This would be unacceptable for a moral rationalist like Sidgwick, who, in requiring self-evidence of his methods would surely also require that their conjunction meet the same requirement. 