Full Idea
The most promising suggestion is that the bundles are tied together by means of memory.
Gist of Idea
Memory is the best proposal as what unites bundles of experiences
Source
A.J. Ayer (The Concept of a Person [1963], §IV)
Book Reference
Ayer,A.J.: 'The Concept of a Person etc' [Macmillan 1973], p.114
A Reaction
This is interesting for showing how Locke was essentially trying to meet (in advance) Hume's 'bundle' scepticism. Hume proposed associations as the unifying factor, instead of memories. Ayer proposes concepts as a candidate.