On deification – 3

“When any created intellect sees the essence of God, the essence of God itself becomes the intelligible form of the intellect … This increase of the intellectual powers is called the illumination of the intellect, as we also call the intelligible object itself by the name of the light of the illumination [lumen vellux]. And this is the light spoken of in the Apocalypse (21:23). The glory of God hath enlightened it – viz., the society of the blessed who see God. By this light the blessed are made deiform – that is, like to God, according to the saying: ‘When He shall appear we shall be like to Him, and we shall see Him as He is’ (1 Jn 2:2)” (Thomas Aquinas, Summa Theologica, Response to I.12,5).