…the grace of deification is entirely unconditional, and there is no faculty whatever in nature capable of achieving it since, if there were, this grace would no longer be grace but merely the manifestation of the operation of a natural capacity. Nor, if deification were in accord with a natural capacity, would there be anything miraculous in it; for then deification would truly be the work of nature, not the gift of God, and a man would be able to be and to be called a God by nature in the full sense of the words.
For the natural capacity of every being is nothing other than the undeviating and natural disposition for active accomplishment. It is, indeed, incomprehensible how deification can raise the person deified outside or beyond himself if it is encompassed within the bounds of nature.
~St Gregory Palamas (Philokalia vol.4, pp.420-421)
Prayerful Life 