Jesus' double question was intended, first, to make the disciples feel the gulf which separated them from the rest of the nation, and so to make them hold the faster by their unshared faith, and be ready to suffer for it, if needful, as probably it would be. It braces true men to know that they are but a little company in the midst of multitudes who laugh at their belief. That Jesus should have seen that it was safe to accentuate the disciples' isolation indicates the reality which He discerned in their faith, imperfect as it was. 'Whom say ye that I am?' Jesus brings them to articulate utterance of the thought that had been slowly gathering distinctness in their minds. We see our beliefs more clearly, and hold them more firmly, when we put them into definite words. The question acted like a chemical element dropped into a solution, which precipitates its solid matter. Nebulous opinions are gathered up into spheres of light by the process of speaking them. That question is all-important for us. Our conceptions of Christ's nature and office determine our relation to Him and our whole cast of life. True, we may say that He is Lord, and not be His disciples, but we are not His disciples as He would have us unless His Messiahship stands out clear and axiomatic in our thoughts of Him. The conviction must pass into feeling, and thence into life, but it must underlie all real discipleship. Doctrine is not Christianity, but it is the foundation of Christianity. The Apostolic confession here is the 'irreducible minimum' of the Christian creed. It does not contain more than Nathanael had said at the beginning, but here it is spoken, not as Peter's private belief, but he is the mouthpiece of all. 'Whether it were I or they, so we' believe. This confession summed up the previous development of the disciples, and so marked the end of one stage and the beginning of another. Christ would have them, as it were, take stock of their convictions, as preliminary to opening a new chapter of teaching. II. That new chapter follows at once. The belief in Him as Messiah is the first story of the building, and the second is next piled on it. The new lesson was a hard one for men whose hopes were coloured by Jewish dreams of a kingdom. They had to see all these vulgar visions melting away, and to face a stern, sad reality. The very fact that He was the Messiah necessarily drew after it the fact of suffering. Whence did the 'must' arise? From the divine purpose, from the necessities of the case, and the aim of His mission. These had shaped prophetic utterances, and hence there was yet another form of the 'must,' namely, the necessity for the Messiah's fulfilling these predictions.