he Orthodox doctrine of theosis, according to John Paul II, is perhaps the greatest gift of the Eastern Church to the West, but one that has largely been ignored or even denied. The Eastern fathers of the Church believed that we could experience real and transformative union with God. This is in fact the supreme goal of human life and the very meaning of salvation–not only later, but now and later. Theosis refers to the shared deification or divinization of creation, particularly with the human soul where it can happen consciously and lovingly.
St. Gregory of Nazianzus (330-390) emphasized that deification does not mean we become God, but that we do objectively participate in God’s nature. We are created to share in the life-flow of Trinity. Salvation isn’t about replacing our human nature with a fully divine nature, but growing within our very earthiness and embodiedness to live more and more in the ways of love and grace, so that it comes “naturally” to us and is our deepest nature. This does not mean we are humanly or perfectly whole or psychologically unwounded, but it has to do with an objective identity in God that we can always call upon and return to without fail. Some doctrine of divinization is the basis for any reliable hope and any continual growth.
Remember what I shared last week about stages and states. Divinized people live in a grateful state of their undeserved union with God, but that does not always mean their stage of human development is without very real limits and faults. This is a distinction that the West, with its dualistic mind, seemed unable to make.
This is how a few ancients and contemporaries understand theosis:
Full salvation is finally universal belonging and universal connecting. Our word for that is “heaven.”
 Pope John Paul II, Orientale Lumen: Apostolic Letter on the Eastern Churches (1995).
 Maximus the Confessor as quoted by John Meyendorff, St. Gregory Palamas and Orthodox Spirituality (St. Vladimir’s Seminary Press: 1974), 39.
 Olivier Clement, The Roots of Christian Mysticism (New City Press: 2013), 37.
 J.A. McGuckin, The Strategic Adaptation of Deification in the Cappadocians, appearing in Michael Christensen, et al. eds., Partakers of the Divine Nature: The History and Development of Deification in the Christian Tradition, (Baker Academic: 2007), 96. (Partakers of the Divine Nature book is the best summary I have read on the subject of theosis.)