''See also:'' [[Desert Fathers]], [[Hesychasm]], [[Maximus the Confessor]], [[Monasticism]]

In western Catholic theology, ''theosis'' refers to a specific and rather advanced phase of contemplation of God. [http://www.newadvent.org/cathen/10663b.htm] The process of arriving to such a state, or moving toward it (as arrival there is not necessary for [[salvation]]), involves different types of prayer which are recognized as beneficial. Various stages of prayer life are recognized as being likely to occur should a person respond to faith by moving along the purgative, illuminative, and unitive ways. See [[ascetical theology]].

It is, therefore, a mistake to attribute to Eastern Orthodoxy a special insight into the existence of the possibility of union with God: the theological difference between east and west is rhetorical. Whether or not eastern liturgies are more conducive to ''theosis'' is another matter; in the west there has been much discussion of the merits of the [[Novus Ordo Missae]]. The [[Tridentine Mass]] is available in hundreds of locations and is very much conducive, if for some faithful the Novus Ordo is not, to the kind of prayer life that leads one along toward ''theosis''. Virtually all spiritual books of any consequence published in the west manifest overt awareness of all the issues comprised in ''theosis'' (some books may focus on specific stages and treat unitive themes more briefly).

''Theosis'' as a concept is used among [[Methodist]]s [http://www.frimmin.com/faith/theosis.html] especially in relation to the [[pietism|pietist]] movement and in the distinctive [[Protestant]] doctrine of ''entire sanctification'' which teaches, in summary, that it is the Christian's goal, in principle possible to achieve, to live without any [[sin]]. In [[1311]] the [[Council of Vienne]] declared this notion, "that man in this present life can acquire so great and such a degree of perfection that he will be rendered inwardly sinless, and that he will not be able to advance farther in grace" (Denziger §471), to be a [[heresy]]. The Protestant conceptions of [[praxis]], [[phronema]], [[ascetical theology]], and [[sacrament]]s are quite different from Catholic and Orthodox understandings, but the use of the term ''theosis'' may <!-- only "may" because the conception of perfection may reflect a radical difference, depending upon the theological tract being compared-->illustrate a commonality of objective or hope.

The doctrine of theosis or deification in [[Church of Jesus Christ of Latter-day Saints|The Church of Jesus Christ of Latter-day Saints]] differs significantly from the '''theosis''' of Orthodox Christianity. In Mormonism it is usually referred to as ''[[exaltation]]'' or ''eternal life''. While the primary focus of Mormonism is on the [[atonement]] of Jesus Christ, the reason for the [[atonement]] is exaltation which goes beyond mere [[salvation]]. All men will be saved from [[sin]] and [[death]], but only those who are sufficiently [[obedient]] and accept the atonement of Jesus Christ before the [[judgment]] will be exalted.