If Augustine had gone to India during his gap year and become acquainted with Advaita Vedanta and the Triple Canon it would be perfectly obvious where the influence for his theory of illumination came from. The Gita Chapter 15 played a role:
In the world of living souls, a small part of me, becoming an individual eternal soul, draws to itself the five senses and the mind, which exist in material nature.
Verse 9: Overseeing hearing, sight, touch, taste, smell, and the mind, he makes use of the objects of the senses.
Verse 15: I am fixed in the hearts of all; from me comes memory, knowledge, and reasoning. I am to be known through all the Vedas, I make the Vedanta, I know the Veda.
Clearly in the Christian redaction Augustine moved from the impersonal all pervasive sat (being/truth) to the individually infused illumination but there is a permanent possibility of insight because the divine is near at hand.