 For granting that the thinking Substance in Man must be necessarily suppos’d immaterial, ‘tis evident, that immaterial thinking thing may sometimes part with its past consciousness, and be restored to it again, as appears in the forgetfulness Men often have of their past Actions, and the Mind many times recovers the memory of a past consciousness, which it had lost for twenty Years together. Make these intervals of Memory and Forgetfulness to take their turns regularly by Day and Night, and you have two Persons with the same immaterial Spirit, as much as in the former instance two Persons with the same Body. So that self is not determined by Identity or Diversity of Substance…but only by identity of consciousness. (L-N 2.27.23) 