Full Idea
One thing cannot have two beginnings of existence, nor two things one beginning. …That therefore that had one beginning is the same thing, and that which had a different beginning in time and place from that, is not the same but divers.
Gist of Idea
One thing cannot have two beginnings of existence, nor two things one beginning
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.27.01)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.328
A Reaction
Chris Hughes has a nice example of a bicycle which is dismantled, parts are swapped with another, then the originals collected up and reassembled, which appears to give the bike two beginnings. This is necessity of origin, not essentiality.