I recently had the pleasure to be present at the Bar Mitzvah of the son of a good friend. The pleasure was enhanced by the fact that the friend and I both hail from the UK and have found ourselves in exile in Philadelphia. Only those who have emigrated to a foreign country can understand what a pleasure it is to be able to spend time with a fellow ex-pat, reminiscing about all manner of trivia, from the English Premier League to pickled onions and decent bacon. That my friend is Jewish and not a Christian simply adds to the pleasure of being in his presence: I do not have to talk about the politics and disputes of the Christian world. Rugby and warm beer are comparatively pure and simple as topics of discussion in comparison to contemporary ecclesiastical conflicts.

The day as a whole was most memorable, and it was a great privilege to have been invited. Numerous high points stand out: during the service, the cantor sang the psalms in Hebrew with such feeling and emotion; and then at the reception afterwards the music and dancing, from traditional Jewish melodies to cover versions of some classic Rolling Stones numbers, was a useful reminder that religion, joy, and vitality are not mutually exclusive categories, whatever the mainstream of American conservative Protestantism might like to claim.

The most profound moment of the day, however, was without doubt the homily which the rabbi preached on Genesis 22, the sacrifice of Isaac. This is a text, of course, which has preoccupied some of the greatest theological minds, Jewish and Christian, throughout the centuries. Indeed, the Danish philosopher-theologian, Soren Kierkegaard, wrote one of his most famous treatises, Fear and Trembling, on this very passage. The problems with the text are numerous, obvious, and profound: how can the promise to Abraham be fulfilled if Isaac is to be slaughtered on an altar? Why does the command not cause Abraham to doubt the sincerity of God? And, above all, how can God command Abraham to do something which is so clearly abhorred in other parts of scripture? Is God capricious, mysterious, or both?

The rabbi's homily addressed each of these issues in turn and culminated in the expected rhetorical question, uttered in a hushed, spine-chilling whisper: what kind of a God demands that a man sacrifice his own son? And that is where it ended. Not even Kierkegaard could have generated the kind of angst which that final sentence created in the congregation, as we stared as it were into the abyss of an unknown, unknowable, yet awesomely powerful and arbitrary God. And that's where he left us, teetering on the brink of oblivion.

Close, I thought, but no cigar. Up until the moment when the homily ended, it could have been preached by a Christian. The rabbi kept close to the words of scripture, following the narrative as laid out in the text very faithfully; in addition, the issues which he addressed were the kind of universal theological and existential questions that the story obviously raises; but then, at the climactic moment, when he asked the obvious question, he signally failed to provide the obvious answer.

The divine command to sacrifice Isaac is extreme, but it brings to the fore the deep mysteriousness of God's relationship to fallen creation. Human expectations of God, who he is and how he acts, are thrown into chaos by the Fall. As human beings who are designed to find their transcendence in an uninterrupted relationship with their Creator are turned in on themselves, so the universe itself becomes dysfunctional and disastrous. Life is full not of sweet communion with God and with fellow creatures but with pain, opposition, and frustration. Throw into the mix the kind of bizarre and terrifying command which God gave to Abraham, and the vertiginous absurdity of life comes starkly to the fore. Now, while it would be a sure sign of criminal insanity today for anyone to think that God has commanded them to murder their child, we can yet identify with the confusion and pain which Abraham must have felt. Of course, someone might well respond that the text gives reason to believe that Abraham had hope all along, but is hope necessarily less painful than despair? Sometimes knowing that there is a chance things will turn out all right is worse than knowing the game is well and truly up. As one friend in tough circumstances once put it to me, `I don't mind despair; it's the hope I can't stand!' Whatever the case, the story alerts us to the fact that even those who are close to God can and do often experience this world, and God's presence in it, as something awesome, confusing, and unnerving.

All this the rabbi had nailed down. He even pointed out the strange absence of Isaac on the return journey (Gn, 22:19) after two earlier verses emphasise the togetherness of Abraham and his son as they head towards Moriah (Gn. 22:6, 8). This, he speculated (entirely reasonably, so it seems to me), possibly indicates that the father-son relationship was somewhat disrupted by the son's realization of what his father had been intending to do to him. Yet the rabbi's theology ended at the yawning chasm of divine absurdity: an unknown, capricious God playing games with his chosen creature. Close, but no cigar.

Christian theology , however, cannot leave the story at the point where the ram suddenly appears like some deus ex machina to give a trite resolution to the complexity of Abraham's situation; nor can it stop with the apparently disrupted relationship between father and son on the journey back home. Christian theology sees the demands being set before Abraham as pointing clearly to the demands which God sets before himself. Indeed, this is one of those beautiful moments when systematic theology and biblical theology mesh into a delightful whole. As systematic theology draws from scripture's ontological implications and provides us with the doctrine of the Trinity, with our understanding of God as Father, Son and Holy Spirit; so biblical theology provides us with the overarching story of God's saving actions in history, helps to connect the life of Abraham to the life of Christ, and, perhaps above all, points us to the God who sacrifices his own Son and then vindicates him through resurrection. Christ is sacrificed, yet death cannot hold him; therein lies the Christian hope. In this context, to neglect either one, the systematic or the biblical, is to evacuate the story of Abraham and Isaac of much of its meaning: without an understanding of God as Trinity, the Father-Son connection disappears; without the story of Jesus Christ, the Genesis narrative appears merely as evidence of the capricious cruelty of a god who plays malicious games with those he claims to love.

Now all this is not to say that the doctrine of the Trinity and the story of Jesus Christ solve all of the theological problems which Genesis 22 throws our way. The depths of God's motivation in the incident are hidden from our eyes, and on this level the story is a reminder of the awesome mystery of God's ways and of our need to depend upon God's revelation in order to understand who he is. Yet, given Christianity's trinitarianism and its gospel, we can offer an answer to the rabbi's question. What kind of a God demands that a man sacrifice his own son? The kind of God who spares not his own son, his only son, the son whom he loves.

We need to be careful here, of course. It is not the fact that God knows what it is to sacrifice his own son that somehow makes it all right for him to demand the same of Abraham. A version of that kind of argument has been used in recent decades to offer an answer to the problem of suffering: God is justified before men and women relative to suffering because he himself suffered in the person of Jesus Christ upon the cross. This argument is only helpful at the most superficial level; deeper reflection makes its flaws somewhat obvious because it does not really solve the problem of suffering at all. If I have cancer and I go to my physician, it does little good for her to tell me that I should not worry because she has cancer too and knows what I am experiencing. I want someone who can cure me; not someone who can understand the pain through which I am going. That God has a problem with suffering too brings little comfort to those who groan under the weight of a fallen creation.

No. The story of Genesis 22 does not connect to the death of Christ in that way. Rather, it draws the reader into the life of Abraham, the intimacy of his relationship with his son, the resoluteness of his journey to Moriah, the agony of soul and confusion he must have felt as he bound his son and raised the knife. It thus intimates to us the incomprehensible trauma of such a sacrifice, especially given the fact that God appears to have willed it so to be; and in doing so, as we turn to God manifest in the flesh of Christ, the story of Abraham and Isaac prepares us for, and then underscores, the incomprehensible costliness of God's grace in Jesus Christ. Yes, it does remind us of the transcendent mystery of God's will and his ways but not in a way that leaves us teetering on the terrifying precipice of theological or epistemological nihilism; instead, it points us to the awesome and inscrutable ways in which God's saving mercy towards us will be manifest in history in the life and work of Christ. There can be no Christmas-style sentimentality about such a divine Father or such a Son; the only response is surely an awed silence in the presence of such terrifying, gracious, merciful mystery.

That Saturday, the rabbi came tantalizingly close to understanding Genesis 22. In many ways, his sermon was a great help to me in understanding aspects of the passage better; but in the end, he did not - indeed, he could not - point me to Christ, only to an unknown and capricious God who tested Abraham in the cruelest of ways. I made that connection for myself, and left the synagogue awed once again by the grace of God the Father made manifest in Christ. The rabbi came close, very close; but ultimately no cigar.