Distinguishing between sanctification and deification

When dealing with the Church Fathers, especially those of the primitive Church, we need to keep in mind that differences exist in their language and use of such language, in terms of addressing the mere sanctification of man and his deification through theosis. Specifically, “where we find references to human participation in divine life, there we assuredly have a claim specifically of theosis. This kind of claim regarding participation in divine life is carefully to be distinguished, however, from the idea of divine indwelling in the human person. Both schemes of sanctification draw on the notion of union, but whereas the latter locates sanctification within the creature and in via, the former [deification] locates it at the level of the divine and insists upon the inseparability of life in via and in patria . . . [A marker of] the doctrine, then, is the union of God and humanity, when this union is conceived as humanity’s incorporation into God, rather than God’s into humanity, and when conceived as the destiny of humanity generally rather than the extraordinary experience of the few” (Williams, A. N. 1999. The ground of union: Deification in Aquinas and Palamas).