Full Idea
In souls there is no mingling of ingredients, nothing of two-fold nature, so it is impossible for the soul to be divided; impossible, therefore, for it to perish either; for perishing is like the separation of parts which were maintained in union.
Gist of Idea
The soul has a single nature, so it cannot be divided, and hence it cannot perish
Source
M. Tullius Cicero (Tusculan Disputations [c.44 BCE], I.xxix.71)
Book Reference
Cicero: 'Tusculan Disputations', ed/tr. King,J.E. [Harvard Loeb 1927], p.83
A Reaction
Cicero knows he is pushing his luck in asserting that perishing is a sort of division. Why can't something be there one moment and gone the next? He appears to be in close agreement with Descartes about being a 'thinking thing'.