Full Idea
Locke's theory implies one person could shift between twenty intelligent beings, and one intelligent being could fragment mentally into twenty different persons, which is ridiculous.
Gist of Idea
If identity is consciousness, could a person move between bodies or fragment into parts?
Source
comment on John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.27.13) by Thomas Reid - Essays on Intellectual Powers 3: Memory Ch 6
Book Reference
'Personal Identity', ed/tr. Perry,John [University of California 1975], p.114
A Reaction
Locke only says that IF the person 'shifted', that would not alter our notion that one person existed here, as long as the consciousness remained the same. The notion of 'fragmenting', though, leads to Parfit saying that personal identity is unimportant.