I am currently reading the Screwtape Letters by C.S. Lewis. It is a book of letters from a mid-level demon in hell to his nephew - a temptor on earth. This portion of a letter stood out to me and re-enforces the idea of free will... so much that even a minion of the Enemy knows it to be true.
I have only just started the book, but I already recommend it!
When reading, the Enemy is actually our Lord and Father! Creature, patient and human are all us, as people. And our father below is Satan. Remember, this is from a demon.
"One must face the fact that all the talk about His love for men, and His service being perfect freedom, is not (as one would gladly believe) mere propaganda, but an appalling truth. He really does want to fill the universe with a lot of loathsome little replicas of Himself - creatures whose life, on its miniature scale, will be qualitatively like His own, not because He has absorbed them but because their wills freely conform to His. We want cattle who can finally become food; he wants servants who can finally become sons. We want to suck in, He wants to give out. We are empty and would be filled; He is full and flows over. Our war aim is a world in which our father below has drawn all other beings into himself: the Enemy wants a world full of beings united to Him but still distinct
....
And that is where the troughs (trials or low points) come in. You must have often wondered why the Enemy does not make more use of His power to be sensibly present to human souls in any degree He chooses and at any moment. But you now see that the Irresistible and the Indisputable are the two weapons which the very nature of his scheme forbids Him to use. Merely to override a human will (as His felt presence in any but the faintest and most mitigated degree would certainly do) would be for Him useless. He cannot ravish, He can only woo. For His ignoble idea is to eat the cake and have it; the creatures are to be one with Him, but yet themselves; merely to cancel them, or assimilate them, will not serve. He is prepared to do a little overriding at the beginning. He will set them off with communications of His presence which, though faint, seem great to them, with emotional sweetness, and easy conquest over temptation. But He never allows this state of affairs to last long. Sooner or later He withdraws, if not in fact, at least from their conscious experience, all those supports and incentives. He leaves the creature to stand up on its own legs - to carry out from the will alone duties which have long lost all relish. It is during such trough periods, much more than the peak periods, that it is growing into the sort of creature He wants it to be. Hence the prayers offered in the state of dryness are those which please Him best. We can drag our patients along by continual tempting, because we design them only for the table, and the more their will is interfered with the better. He cannot "tempt" to virtue as we do to vice. He wants them to learn to walk and must therefore take away His hand; and if only the will to walk is really there He is pleased even with their stumbles. Do not be deceived. Our case is never more in danger than when a human, no longer desiring, but still intending, to do our Enemy's will, looks round upon a universe from which every trace of Him seems to have vanished, and asks why he has been forsake, and still obeys."
