Of God and His Creatures
Of the Immutability of the Will of Souls detained in Purgatory BUT because there are souls which in the instant of their parting do not arrive at happiness, and yet are not damned, we must show that even these souls cannot change their purpose after parting from their bodies; and the proof is this: -- the souls of the blessed and of the lost have their will immutably fixed according to the end to which they have adhered. But the souls that carry with them into the next world some matter for purgatory are not ultimately in a different case from the blessed, for they die in charity, whereby we adhere to God as to our last end. Therefore they too will have their will immutably fixed.

4.93 : That the Souls of the Wicked after Death have their Will immutably fixed on Evil
4.95 : Of the General Cause of Immutability in all Souls after their Separation from the Body