What is deification?
Deification is the attaining of likeness to God and union with Him so far as is possible (Dionysus the Aeropagite, EH 1.3, PG 3.376a).
God, you see, wants to make you a god; not by nature, of course, like the One whom He begot but by His gift and by adoption (Augustine of Hippo, Serm. 166.4).
Deification can be defined as “God’s perfect and full penetration of man” (Staniloae, 2002, p. 362). The deification or divinization of man is not “an identification with God; it is only an assimilation, a very eminent restoration of the original divine likeness…[whereby one] participates by grace in the perfections that God possesses by nature . . . The Spirit transforms the soul to the image of the Logos, the natural Son of God, thus making the Christian an adoptive child of God. Affecting, it seems the very essence of the soul, this mysterious conformation is not of a moral nature only but of a physical nature; it is a veritable partaking of the divine nature and of the divine life” (Gross, 1938/2002, p. 272).
Deification is the
enhypostatic and direct illumination which has no beginning but appears in those worthy as something exceeding their comprehension. It is indeed a mystical union with God beyond intellect and reason, in the age when creatures will no longer know corruption. Thanks to this union, the saints, observing the light of the hidden and more-than-ineffable glory become themselves able to receive the blessed purity, in company with celestial powers. Deification is also the invocation of the great God and Father, the symbol of the authentic and real adoption, according to the gift and grace of the Holy Spirit, thanks to the bestowal of which grace the saints become and will remain the sons of God (Maximus the Confessor, Ad Th. 61, PG 90, 636C; Schol. 16, PG 90, 644C).
Maximus (Chapt, 2.88) added that
the soul becomes god and rests from all its mental and physical works by participation in divine grace; at the same time all the natural operations of the body rest with it. They are deified along with the soul in proportion to its participation in the deification, to the extent that then only God will be visible, through the soul as well as through the body; the natural attributes are conquered by the overabundance of glory.
Deification, then, is
both the light encountered (inasmuch as it is a visible apparition) and something that attaches to the person, becoming one with her and changing her. It is both God as other and God transforming the human person from within (Williams, 1999, p. 105).
Deification results in the theoria of the uncreated light (Lossky, 1967/1974), because its processes are directly related to theosis – the vision of the divine light (Lossky, 1944/1976, 1983).
Deification and Man
When Adam was first created, the Spirit of God clothed him in holiness and made him a perfect person. However, such perfection was not absolute but relative, in order that Adam and his descendants could “progress peacefully and rise up toward the perfect…to draw closer to the Unbegotten” (Irenaeus of Lyon, Adv. Haer. 3.23.5 ).
It was progressive deification that was originally intended for mankind and presented to our first parent (Gross, J. 1938/2002; Symeon the New Theologian, 1994). But after Adam sinned (Gn 3:1-24), it was Christ, the new Adam, who reopened the gate for the deification of mankind through the three spiritual stages of purification (of the heart), illumination (of the heart of the soul, the nous) and deification.