Full Idea
There are no individuating marks which could serve to differentiate one Soul from another.
Gist of Idea
No individuating marks distinguish between Souls
Source
Jenny Teichmann (The Mind and the Soul [1974], Ch.2)
Book Reference
Teichmann,Jenny: 'The Mind and the Soul' [RKP 1974], p.16
A Reaction
Presumably they could have at least much identity as two different electrons (if they are in space-time?). It is hard to see why anyone would be interested in their 'own' immortality, if loss of all individuality was a condition.