TIME according to CS LEWIS

"Of course, you and I tend to take it for granted that this Time series--this arrangement of past, present, and future-- is not simply the way life comes to us but the way all things really exist. We tend to assume that the whole universe and God Himself are always moving on from past to future just as we do. But many learned men do not agree with that. It was first the Theologians that started the idea that some things are not in time at all: Later the Philosophers took it over: now some of the scientists are doing the same. Almost certainly God is not in Time. His life does not consist of moments following one another... This is difficult I know.

Suppose I am writing a novel. I write, "Mary set down her work; next moment there came a knock at the door!" For Mary who has to live in the imaginary time of my novel there is no interval between putting down her work and hearing a knock. But I, who am Mary's maker, do not live in that Imaginary time at all. Between writing the first time of that sentence and the second, I might sit down for three hours and think steadily about Mary. I could think about Mary as if she were the only character in the book, and the hours I spent in doing so would not appear in Mary's time (the time inside her story, at all.

It is not a perfect illustration, of course, but it may give you a glimpse of what I believe to be the Truth. God is not hurried along the time stream of the universe any more than the author is hurried along in the imaginary time of his own novel.

A difficulty we get if we believe God to be in time is this. [Most] everyone who believes in God at all believes He knows what you and I are going to do tomorrow. But if He knows that I am going to do so-and-so, how can I be free to do otherwise? Well, here once again, the difficulty comes from thinking God progresses along the Time-line like us; the only difference being that He can see ahead and we cannot. Well, if that were true, and God forsaw our acts, it would be very hard to understand how we could be free not to do them. But suppose God is outside and above the time-line. In that case, what we call "Tomorrow" is visible for Him in just the same way as what we call "Today." All these are "Now" for Him. He does not remember what you are doing yesterday; he simply sees you doing them: because, though tomorrow is not yet there for you, it is for Him. You never supposed that your actions for this moment were any less free because God knows what you are doing. Well, He knows your tomorrow's actions in just the same way--because He is already in tomorrow and can simply watch you. In a sense, He does not know your action till you have done it: but then the moment at which you have done it is already "Now" for Him.
This idea has helped me a good deal. If it does not help you, leave it alone... you can be a perfectly good Christian without accepting it, or indeed, without thinking about the matter at all.
~MERE CHRISTIANITY