I too was taught that differences between traditions, and especially between east and west, are due to the different emphases along what, for lack of a better term, is called the Christ event: birth-to-ascension. Over that, I lay the linguistic, political, and geographic differences that have shaped and separated both halves. I would add, on my own, that the east seems to properly begin with the community whereas the west has been fascinated by the individual and individualism to our very day. (He drummed his fingers on the table in muted staccato.)
You are right that the east is not as interested in how to be cleansed and more in how to live a holy life. The high example of that for EO are the monks of Mount Athos. EO kept the monasticism that Luther democratized in the West. It also retained a Neoplatonic core that the west gave up for Aristotelianism in the fourteenth century w Thomas Aquinas.
Let's separate mysticism from theosis (deification is a Latin term which doesn't quite ring with the right overtones.) Theosis, the doctrine that the new humanity is made like God, is definitely front-and-center in EO. Funny enough, it is in the west as well. A couple of decades ago, scholars started finding it in the Reformers--especially Calvin. Theosis has been in the west all this time as well. When we talk about the imago Dei's renewal in the sanctification process, the end goal where this is going is Christlikeness or theosis. I asked Tom Wright about it probably ten years ago now, and he affirmed that theosis is not only permissible but biblical. That said, it is NOT becoming a God or God, it is becoming like God: being made in the image of his Son.
That is why I don't like deification. It doesn't leave enough difference in the undertones and it suggests that one, in our own track, can improve and improve until one finally arrives at divinity. This is a kind of Mormon or New Age or New Thought or some brand of Wesleyan perfectionism. I prefer theosis because it keeps a note of distinction in between that which is by nature and that which is by grace.
(At this point, Dr. Ehrmstuhl remembered me. We exchanged some whispered pleasantries, and he assured me he was almost done. But, whomever he was talking to seems to have hit a nerve, and the doctor's attention swiveled back to the conversation.)
Mysticism is a style of discipleship which often refers to saints in the tradition who emphasized prayer and ascetic discipline, figures like Theresa of Avila, San Juan de la Cruz, Francois Fenelon, Catherine of Siena, or anchorites like Richard Rolle or Julian of Norwich, and many others. But mysticism is a slippery word. Evelyn Underhill lays it all out in her work on mysticism. There are dangers here. You could be a neopagan and practice this, or a Buddhist or whatever. A deep question in my project is what to do with mysticism in the Christian tradition. Should we jettison it or not? Should mysticism even exists where the Solas exist? The short answer: a highly qualified yes. I do not agree with the hesychastic approach of the EO. They seek the uncreated light born of the energies of the Trinity. I think it is the ever-flowing agape life of the Spirit (Augustine's maestro) who calls us in the solas always higher up and further in. When theology turns its gaze there, it becomes apophatic--it can only say what is not.
(Here, his interlocutor took up the challenge. The Doctor swiveled in his chair. He finally broke in:) There is a Mount Athos documentary on YouTube. It is good. (More from the other side.) Hesychasm has nothing to do with the solas. I was using the solas as a part/whole to mean the framework of Reformed theology. Oh yes, a synecdoche--good catch! What I mean by that is that, because of that Neoplatonic core, EO developed a mysticism that is different than the mysticism of the West. And so I do not find their way into prayer a live option. What I know of it seems a way wholly apart from scripture. It risks keeping the divine Jesus and not the man. Or it might avoid Jesus altogether and try to climb on the rope of the Spirit alone. Therefore, it rings alarms in my head, not least of which is the alarm of gnosticism. I am not saying that EO monks are gnostics. They would probably be quick to shut that down. I'm just saying that it makes me nervous.
The whole essences and energies things comes out of Neoplatonic problems with the doctrine of the Trinity: how does the ineffable God have anything to do with finitude? The thinker here is Gregory of Palamas. (The doctor got up and rummaged around on his shelves.) The general understanding these days is that this language is strange to Western ears, but that it is orthodox. Trinitarian thinkers, EO or Western, are getting at the same thing. I read Palamas in that slim Classics of Western Theology volume. His isn't language I'm adopting anytime soon, but okay. One is stuck with the tradition you grew up with. I am okay attempting to be an informed Westerner.
(Here, again, his interlocutor took up the conversation for some distance.) Your thoughts on individualism and monasticism are good ones. I am not a good guide wading out any deeper into EO waters. I will say this, though. The danger with monasticism is that it has a tendency to create spiritual hierarchies (classism) in the church, and that is going on in EO. I prefer monasticism without hierarchy, and there are models for that even in Protestantism. My own denomination, for example, has various monasteries scattered about, as do other Protestant denominations.
Oh, I completely agree that the path of awakening, purgation, and union is the established way. But it has to be found correctly. Simply put: if it is not in Jesus, it is not available. He is the foundation stone. But not to worry: Paul's language of union with Christ, of being buried with him and raised with him, of being made alive in him: that is the invitation. So the mystic way is not to know nothing and to realize nothing, but to know Christ, following the pull of the Spirit, and to be remade after his image. It is to be invited, because the church has been invited, to the meal that the Trinity has set.
At this point, I got a phone call from my wife. The doctor and I nodded genially, and he may have apologized. And I left.