Feast of the Baptism of Our Lord

I think that we tend to under-rate the importance of this Feast and the event that it celebrates. I seem to recall reading that the Orthodox put much emphasis on Christ's Baptism in the Jordan as being one of the great Trinitatian theophanies - it's one of those rare times when the Three Persons make themselves 'visible'. We hear the voice of God the Father, God the Son Incarnate is baptized, and the Holy Spirit appears in the form of a dove.

Of course, part of the difficulty is in correctly interpreting that baptism. John's baptism was a baptism of repentance, so understanding why Christ submitted to it can cause difficulties. The Arians took Christ's baptism and the fact that He received the Holy Spirit at that time as evidence that He was not equal to the Father. Well-intentioned Christology which seeks to affirm Christ's divinity tends to downplay the importance of the Baptism of the Lord, reducing it to a mere gesture of humility. I'm inclined to think that such an over-simplification of things tends towards monophysitism - a rejection of the dogma of Christ's two natures, human and divine.
On the other hand, other theologians treat the Baptism as though it were the moment when Christ became divine, or as though He were just an ordinary man whose miracles and preaching derived purely from His having received the Holy Spirit at that time. Similarly, whilst it is evident that this Baptism was hugely significant in Our Lord's beginning his public mission, it would be a mistake to treat it as being the vocation-moment in His life when He realised who He was and what He had to do.

So, what is the Christological significance of the Baptism? Well, I shan't attempt to give a comprehensive answer, but I will highlight some aspects which strike me as important. Firstly, whilst Christ was sinless and not in need of forgiveness, I think that we can understand undergoing John's baptism as being more than just a gesture of humility or solidarity with the mass of sinful humanity. Rather, Christ is the Head of the Church and assumed a human nature which was marked by Adam's sin. He did not have the stain of Original Sin or the concupiscence which comes from it, but he did assume many weaknesses to which man is subject as a result of the Fall. It was therefore fitting that the Head of the Church should take part in the Baptism of repentance and thereby bring the Body with Him. Of course, it is the sacrifice of the Head which makes possible the repentance and salvation of the Body.
The Baptism is also profoundly a sign of acceptance - a prefigurement of His redeeming death. The logic of our sacramental relationship with Christ means that it makes perfect sense that if His baptism is a sign of His acceptance of His death, that our baptism allows us to share in the benefits of that sacrifice.