Theological Mystery

There are several glorious truths of the Christian faith that I would call mystery: The trinity, predestination and salvation by faith along with several others. Now I have often wanted to explain what I mean by that, and that this mysteriousness does not mean that we must not seek to look into these things and know more about them. Well I have found someone speaking of it who is far more wise, intelligent and able than I to give some insight to this 'theological mystery' J I Packer. Read his words as he speaks about it with particular attention to the doctrine of atonement:

What sort of knowledge of God’s action in Christ’s death may we have? That a man named Jesus was crucified under Pontius Pilate about AD 30 is common historical knowledge, but Christian beliefs about his divine identity and the significance of his dying cannot be deduced from that fact alone. What further sort of knowledge about the cross, then, may Christians enjoy?
The answer, we may say, is faith-knowledge: by faith we know that God was in Christ reconciling the world to himself. Yes, indeed; but what sort of knowledge is faith-knowledge? It is a kind of knowledge of which God is both giver and content. It is a Spirit-given acquaintance with divine realities, given through acquaintance with God’s word. It is a kind of knowledge which makes the knower say in one and the same breath both ‘whereas I was blind, now I see’ (Jn 9:25) and also ‘now we see as in a mirror, darkly . . . now I know in part’ (1 Cor. 13:12). For it is a unique kind of knowledge which, though real, is not full; it is knowledge of what is discernible within a circle of light against the background of a larger darkness; it is, in short, knowledge of a mystery, the mystery of the living God at work.
‘Mystery’ is used here as it was by Charles Wesley when he wrote:
‘Tis mystery all! The immortal dies!
Who can explore his strange design? In vain the first-born seraph tries. To sound the depths of love divine!
‘Mystery’ in the sense (traditional in theology) means a reality distinct from us which in our very apprehending of it remains unfathomable to us: a reality which we acknowledge as actual without knowing how it is possible, and which we therefore describe as incomprehensible, Christian metaphysicians, moved by wonder at the world, speak of the created order as ‘imagery’, meaning that there is more to it, and more of God in it, than they can grasp; and similarly Christian theologians, taught by revelation, apply the same word, for parallel reasons to the self-revealed and self-revealing God, and to his work of reconciliation and redemption through Christ.

…Now the atonement is a mystery in the defined sense, one aspect of the total mystery of God. But it does not stand alone in this. Every aspect of God’s reality and work, without exception, is mystery. The eternal Trinity; God’s sovereignty in creation, providence, and grace; the incarnation, exaltation, present reign and approaching return of Jesus Christ; the inspiring of the Holy Scriptures; and the ministry of the Spirit in the Christian and the Church — each of these (to look no further) is a reality beyond our full fathoming, just as the cross is. And theories about any of these things which used human analogies to dispel the dimension of mystery would deserve our distrust, just as rationalistic theories about the cross do.
It must be stressed that the mystery is in each case the reality itself, as distinct from anything in our apprehension of it, and as distinct therefore from our theories, problems, affirmations and denials about it. What makes it a mystery is that creatures like ourselves can comprehend it only in part. To say this does not open the door to scepticism, for our knowledge of divine realities (like our knowledge of each other) is genuine knowledge expressed in notions which, so far as they go, are true. But it does close the door against rationalism, in the sense of theorizing that claims to explain with finality any aspect of God’s way of existing and working. And with that, it alerts us to the fact that the presence in our theology of unsolved problems is not necessarily a reflection on the truth or adequacy of our thoughts. Inadequate and untrue theories do of course exist: a theory (the word comes from theorein, to look at) is a ‘view’ or ‘sight’ of something, and if one’s way of looking at it is perverse one’s view will be distorted, and distorted views are always full of problems. But the mere presence of problems is not enough to prove a view distorted; true views in theology also entail unsolved problems, while any view that was problem-free would certainly be rationalistic and reductionist. True theories in theology, whether about the atonement or anything else, will suspect themselves of being inadequate to their object throughout. One thing that Christians know by faith is that they know only in part.