Full Idea
In cases of our consciousness being interrupted and we losing sight of our past selves, doubt are raised whether we are the same thinking thing, i.e. that same substance or no.
Gist of Idea
If consciousness is interrupted, and we forget our past selves, are we still the same thinking thing?
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.27.10)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.336
A Reaction
Only Locke and Parfit, with their psychological continuity theory, need to anguish over this problem. Personally I see myself as irredeemably an animal, retaining my identity even when I can't remember my own name.