In modern phraseology, St Thomas would say that death sets a bound to man's moral evolution, at least in respect of all specific change. That is true, but can philosophers prove it? What is the proof of the present allegation? St Thomas always seems to regard the soul as, to some extent, crippled by separation from the body. Cf B. II, Chap. LXXV, arg. 1, reply: B. II, Chap. XCIV, nn. 3, 4. For the capabilities of the soul after death, a priori arguments go very little way; and as for experience, it comes to us all, but too late.
Of God and His Creatures: 3.145