I think you actually grasped part of this with your own observation that time moves infinitely backwards and forwards using our notion of timelines as a kind of metaphor. A line for mathematicians is, of course, infinite in both directions. Aquinas postulated something he called aveternity, which is the way angels perceive time—probably a multi-dimensional grasp of time but not eternity. Bear with me as I think aloud about this. I am far better at thinking on paper than in any other medium.
Time as we know it may be like an illusion in that we can only see the tail end of something that indicates a more robust and crackling whole, completely independent of time. When Aristotle and Aquinas described God as the Unmoved Mover—a cause that caused itself or was and is its own existence, the paradox is both revealed and deepened. How can something cause itself or have no beginning? I find it amusing that the definition of energy being neither created nor destroyed (the first law of thermodynamics) is basically a Godless recasting of the same notion. (Occam cutting off his balls to spite his face, so to speak.) This does, in a sense, lead one cautiously to think that perhaps from a more complex multi-dimensional perspective, time would be grasped simply as movement within eternity—something englobed by the eternal—the radical contingency of being postulated by Aquinas with all of us bathed in that strange night of eternity—that vacation that God seems to have taken from Himself in all of us.
There is a curious passage in Aquinas where he refers to the irrelevance of position to the eternal. Since God is everywhere present and at all times and beyond all times, whether we are to the left or right, so to speak of God, (if we could speak so) is inconsequential. We might reason similarly that whether we are at the beginning or the end of our life—that too is irrelevant to God. Wilhelmsen (a professor I had in college) used to argue that God is not waiting around for us to die. We are already present to God—the whole of our lives—before Him. The paradox is that while the timelines mean a great deal to us, they also seem to be meaningless from a lived perspective. We all live our lives, for the most part, as if we will never die--knowing, in a sense, that we will not really die but having to die nonetheless to get to just that certain knowledge. Most of us will probably be surprised by death.
I suspect that we participate in God's own nature with a degree of participation referred to as proper proportionality. This is a relationship between God's Is and our is--the big is and the little is. (Proportionality is more of limit than a rigid definition.) I often think that what we refer to as self is nothing more than our divine identity poorly grasped and apprehended by four dimensional consciousness. All the while, our souls gnash their teeth at the crummy tools that we have at our disposal for further reflection and analysis.
I have been fascinated all my life with the metaphysics of Sonship. What does it really mean to be a child of God, to be a true heir? There is more to this than the usual mumbo jumbo that goes along with such notions as the mystical body of Christ. (A fine concept as a beginning but surely we can do better.) What does it mean for God to know us before we begin to exist in time--the ens diminutum (little being) of Duns Scotus? So many questions, so few answers but the questions are comforting. They can lead one to believe in a God who is far more generous than we hoarders can probably imagine. Time is free, life is free, air and earth are free and we are busy monetizing the gifts. A shame really...
Physics teaches us that two objects cannot occupy the same space. To my simple mind, the withdrawal of God from humanity begins with the gift of our coming into being in time. The Divine, I suspect, cannot make us as it says in Genesis: in "our image" without engaging in something extraordinarily curious: God can only make us heirs to Himself by stepping back and withdrawing, leaving us to discover for ourselves that the door to infinity is always open. The
God is making Himself in a new way in each one of us and I suspect that it would be blasphemous for us to know ourselves as we are in Him without making our acquaintance the hard way. Perhaps in creating us, God experienced some suffering, knowing that he was creating beings who desperately would want to know themselves in Him, desperately need Him and yet at the same time be so secretly puffed up by their own certain knowledge of divinity that they would feel free to dawdle, to focus on anything and everything but the obvious. Perhaps in creating us as true sons and daughters, God has to let go of Himself to be Himself in us and that it takes an infinite forgetting to make something finite, infinite. The cross is present in this sense at our creation. There is a word for this forgetting in the Torah. Tsim Tsum (Divine Withdrawal). God withdraws His infinite fullness, perfection, completeness... to make Makom (place) for the existence of the time/space continuum. What would it be like for God not to be God? Could God know what this would be like without in some way doing it? Perhaps we are all God just taking a little vacation from Himself (: No that is too simplistic but it is kind of funny.
Some theologians actually argue that God voluntarily gives up a portion of His Omnipotence and Omniscience in order to allow MAKOM (Space) for created things (Samsara). This is bordering on Hegelianism but the notion of Tsim Tsum scratches at the door of something worth thinking about. God sure seems to make Himself scarce and there has to be a reason for this beyond the reasons given to us by the dog and pony show of pietistic Christianity.
Sean, me boyo, I think you'll like this question. I have a friend who is a poet, a philosopher, and a lyricist. He asked me to tell him what I meant when I thought of the term "eternity."
This is my response, and I'd certainly be interested in YOURS.
As a young person, even though it is unfathomable to the human mind, I thought of eternity as time moving endlessly in both directions, with no beginning and no end. Time always was, and always will be (like God). The no end part is something you can almost wrap your mind around -- though not quite, because we live in a world full of beginnings and endings, of EVERYTHING.
Time NEVER ending? NEVER? NEVER?!?!? It's actually a terrifying thought.
The no beginning part is much harder part to grasp. Because, for us humans, time seems to go in one direction, forward. So the idea of it continuing forever backwards as well ... hard. I mean, how can something, ANYTHING (like time) have NO BEGINNING?!?! You go so far back, and then you keep going. And going. It's f*cking impossible to grasp.
All that aside, now being an adult who's read Einstein and a fair amount of physics for a layman, I come to another conclusion because I now know that, according to physics, Time (as a dimension, like length and width; and, paradoxically, also possibly an illusion - according to the Buddhists, or the Hindus, I believe) DID have a beginning and it WILL have an end. ["The end of time" - a real forthcoming event.]
So is eternity simply the time that we understand, the dimension of time which exists between the beginning of time and the end of time, which -- though a really f*cking long time -- is still FINITE, and not infinite?
Or does eternity actually describe something broader than just time [time being ultimately finite]? Something that exists outside of time?
(And when you speak of something existing outside of time, it gets a lot harder to grasp. It's like thinking of a 5th or a 6th dimension [which theoretical physicists do, but not me] - I live in a world of height, length, width - so, what is another dimension like?)