The Evangelist's assertion, in St. John 1, that when John the Baptist said "I am not the Christ" it was a confession and not a denial seems odd at first glance, but the Evangelist is emphatic about it, saying it twice. How is it that this is a confession and not a denial? The fact that this is St. John's Gospel is significant, since it is in this fourth Gospel that we have all the "I am" assertions of Jesus. So we have two sides of the faith here: to confess that Jesus is the great I am, the incarnate God, is also be to confess that we cannot arrogate to ourselves merits or righteousness. To say that Jesus is the God who is, the true and only existent God, is also to deny yourself.
Here is the audio of today's sermon (Advent IV).