Is it not written in your Law: I said, you are gods? (Jn 10:34).
He has given us most great and precious promises: that by these you may be made partakers of the divine nature (2 P 1:4).
Two kinds of deification exist. The first kind refers to the
elevation of man to the highest level of his natural powers, or to the full realization of man…[when] the divine power of grace is active in him…[The second kind refers to the] progress which man makes beyond the limits of his natural powers, beyond the boundaries of his nature, to the divine and supernatural level (D. Staniloae, 2002, p. 363).
For man to pass from the first kind of deification which is well-known, to the second kind which is rarely heard about these days in Western Christianity, a leap of grace occurs, because “man too works during the first stage, but during the second, only God” (p. 364).
Thomas Aquinas maintained that in the latter kind of deification,
the gift of grace surpasses every capability of created nature, since it is nothing short of a partaking of the divine nature, which exceeds every other nature . . . God alone should deify, bestowing a partaking of the divine nature by a participated likeness (Summa Theol, 2.1:112.1).
He added that
this name God is communicable, not in its whole signification, but in some part of it by way of similitude so that those are called gods who share in divinity by likeness, according to the text I have said, ‘You are gods (Ps 82:6) (Resp. I.13,9).
Aquinas also declared that
Man’s happiness is twofold…One is proportionate to human nature…The other is a happiness surpassing man’s nature and which man can obtain by the power of God alone, by a kind of participation of the Godhead [ad quam homo sola divina virtute pervenire potest secundum quandam divinitatis participationem], about which it is written (2 P 1:4) that by Christ we are made partakers of the divine nature (Resp. I-II.62,1).
In deification, “the Paraclete illuminates from on high the man who attains in prayer the stage which is superior to the highest natural possibilities and who is awaiting the promise of the Father; and by His revelation ravishes him to contemplation of the light” (Gregory of Palamas, The Triads, II.3.33). Those who experience theoria arising from the process of deification see God in themselves as though they are looking into a mirror.
After undergoing purification and illumination,
God no longer comes to us as before without appearance and without image…He comes under a certain image and yet it is the image of God…[He] makes Himself seen in His simplicity, formed out of formless, incomprehensible, ineffable light…He makes Himself seen clearly, He is perfectly recognizable, He speaks and hears in a way that cannot be expressed. He who is God by nature converses with those whom He has made gods by grace, as a friend converses with His friends, face to face. He loves His sons as a Father; He is loved by them beyond all measure. He becomes in them a wondrous knowledge, a dreadful hearing. They cannot speak of Him as they ought, nor can they any longer keep silence (Symeon the New Theologian, Serm. 90).
The purified, therefore, “contemplate invisible things…they participate in the intelligible gift of the light of God in their impassible and immaterial intelligence” (Gregory of Palamas, The Triads, II.3.26).