When you hear speak of the deifying energy of God and theurgic(theourgia)grace of the Spirit, do not busy yourself or seek to know why it is this or that and not something else; for without it you cannot be united to God, according to those Fathers who have spoken about it. Attend rather to those works which will allow you to attain to it, for thus you will know it according to your capacities; for, as St. Basil tells us, he alone knows the energies of the Spirit who has learnt of them through experience. As for the man who seeks knowledge before works, if he trusts in those who have had the experience, he obtains a certain image of truth. But if he tries to conceive of it by himself, he finds himself deprived even of the image of truth. He then puffs himself up with pride as if he discovered it, and breathes forth his anger against the men of experience as if they were in error. Do not be overcurious threrefore, but follow the men of experience in your works, or at least in your words, remaining content in the exterior manifestations of grace.
Deification is in fact beyond every name. This is why we, who have written much about hesychia (sometimes at the urging of fathers, sometimes in response to the questions of the brothers) have never dared hitherto to write about deification. But now, since there is a necessity to speak, we will speak words of piety (by the grace of the Lord), but words inadequate to describe it. For even when spoken about, deification remains ineffable, and (as the Fathers teach us) can be given a name only by those who have received it. (The Triads E. The Uncreated Glory 32)