Take a look at Metropolitan Hierotheos and his book Orthodox Psychotherapy, especially
this chapter.
Excerpt:
When a person rises from bodily knowledge to the soul’s knowledge and from that to spiritual knowledge, then he sees God and possesses knowledge of God, which is his salvation. Knowledge of God, as will be explained further on, is not intellectual, but existential. That is, one’s whole being is filled with this knowledge of God. But in order to attain it, one’s heart must have been purified, that is, the soul, nous (intellect) and heart must have been healed. “Blessed are the pure in heart, for they shall see God” (Matt.5,8).
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These things show that the vision of God, deification, union and knowledge of God are closely bound together. They cannot be understood apart from one another. Breaking this unity takes man further away from knowledge of God. The basis of Orthodox epistemology is illumination and God’s revelation within the purified heart of man.
As we have seen, knowledge of God is beyond human knowledge. Vision of the uncreated light surpasses all epistemological activity and is “beyond sight and knowledge” (2,3,50). Since vision of the uncreated light is offered to the hearts of the faithful and perfect, that is why “it is superior to the light of knowledge” (2,3,18;CWS p.63). And not only is it superior to the light of human knowledge “from Hellenic studies”, but also the light of this theoria differs from “the light that comes from the Holy Scriptures”, since the light of the Scriptures may be compared to “a lamp that shines in an obscure place, whereas vision of the uncreated light resembles the morning star which shines in the day, that is to say, the sun” (2,3,18;CWS p.63). The grace of deification thus transcends nature, virtue and human knowledge (3,1,27).
