Full Idea
Is one soul, even minutely, more or less of a soul than another? Not in the least.
Clarification
'Soul' is the Greek word 'psuché', which covers mind and consciousness and life
Gist of Idea
One soul can't be more or less of a soul than another
Source
Plato (Phaedo [c.374 BCE], 093b)
Book Reference
Plato: 'The Last Days of Socrates', ed/tr. Tredennick,Hugh [Penguin 1969], p.149
A Reaction
This idea is attractive because unconsciousness and death seem to be abrupt procedures, and so appear to be all-or-nothing, but I would personally view extreme Alzheimer's as an erasing of the soul, though a minimum level of it seems all-or-nothing.