Every spiritual way is concerned with progressing by degrees through a process of spiritual realization. Each way, as such, is composed of a doctrine and a method. The method involved will differ, adjusted as it must be to the spiritual temperament of the person making use of it, who might be predisposed to either bhakti or jnana. For that reason we will attempt no comprehensive overview of the methods proper to each type here.
The doctrine, on the other hand, always remains the same, and in the case of Christianity it is completely summarized in the first chapter of the Gospel of John:
In the beginning was the Word, and the Word was with God, and the Word was God…All things were made by him: and without him was made nothing that was made…And the Word was made flesh, and dwelt among us, (and we saw his glory, the glory as it were of the only begotten of the Father,) full of grace and truth. And of his fullness we all have received, and grace for grace.
I am the way, and the truth, and the life. No man cometh to the Father, but by me…from henceforth you shall know him, and you have seen him…he that seeth me seeth the Father also.
These passages, as enunciated by the Fathers, provide us with the doctrine of the Logos, which is elaborated as follows:
Christ has two natures. These can be described as the Uncreated Logos by which Christ is fully God, and the created Logos by which He is made manifest and is fully human. His personality, however, is singular: one person, two natures.
By integrating into himself all that is God and all that is man, he took from potency to act what is in every other man only potency: to say it another way, he restored humanity to perfection through his passion. If sin is envisaged as separation from the divine, redemption is a real reintegration of the human into the divine. This is called deification or theosis, and this is Christ’s gift to man, which was a gift of Himself, since he would become the gateway to Divinity, and stated as much by saying that ‘no one comes to the Father but through me.’
We will pause here to note that the founders of the various religions (at least those who acknowledge a founder) general describe themselves in this way, each claiming by this their status as personification of the Logos. And so the Buddha “He who sees the Dharma sees me, and he who sees me sees the Dharma,” while Muhammad said, “He that hath seen me, hath seen God.”
He blazed for all them the trail to do the same, and called them forth to travel it in imitation of Him. What Christ accomplished, all are invited to accomplish in Him and through Him and by Him.
Here again we will point out that as Christians we are not merely following the moral precepts of a teacher, but are called to become Christs. We are called to repeat within ourselves the drama of the Passion, participating in Christ’s work by becoming integrated into Him and through Him with the Absolute, being as he is the only possibly means of achieving this union.
The ultimate goal of the mystical way is aptly summarized in section 460 of the Catechism of the Catholic Church, the gravity of which cannot be overstated (numbered footnotes are mine):
The Word became flesh to make us “partakers of the divine nature”: “For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God.” “For the Son of God became man so that we might become God.” “The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods.”
Now we must conclude: either the Church and the Fathers of the Church are prone to an exaggeration that borders on recklessness, or else there is a deifying reality present in Christian salvation that is a bit more profound than the common understanding of the term, as some kind of legal pardon, would lead us to believe. This necessitates at least brief mention of theosis, or divinization.
 John 1:1-16.
 John 14:6-9.
 1 Peter 1:4.
 St. Irenaeus, Adv. Haeres. 3, 19, 1.
 St. Athanasius, De inc. 54, 3.
 St. Thomas Aquinas, Opusc. 57, 1-4.