Nock's commentary, again: "It is not stated here, but it follows from [Ch. X], that reasonable and unreasonable soul exist simultaneously in a man; this is a commonplace of Hellenistic philosophy. In Iamblichus also it is complementary to the general belief in two kinds of soul; so in the Poimandres man is assigned a dual nature. The struggle of the reasonable soul and the unreasonable is again a commonplace."

The Pœmandres is an important Hermetic text. I read it a few years ago, but remember little about it.

I will note that the struggle between one's divine ("good") and mortal ("evil") halves was a big part of my Christian upbringing, too. Personally, I find the whole thing baffling, and it's a significant component of my apostasy.