Full Idea
If identity of soul makes the same man, and the same individual spirit may be united to different bodies, it is possible men living in distant ages may have been the same man. But if the soul of Heliogabalus is in a hog, we would not say a hog is a man.
Gist of Idea
If the soul individuates a man, and souls are transferable, then a hog could be a man
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.27.06)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.332
A Reaction
[compressed] Locke uses this to say that Heliogabalus remains Heliogabalus, despite being in a hog. This is a good case of conceivability being very misleading about actual possibility. If Heliogabalus is transferable, then of course he isn't physical.