Christianity comes to us with the claim to be the revelation of a mystery. Our Lord in the gospel speaks of the ‘mystery of the Kingdom of God': and declares that this has been made known to his disciples (Mark 4, 11). St Paul speaks of the gospel as a ‘revelation of the mystery, which in ages past was kept secret, but now has been made manifest and through the writings of the prophets has by the command of the everlasting God been made known to all the nations’ (Rom. 1, 4). Elsewhere he speaks of ‘the mystery which has been hidden from former ages and generations, but now has been made manifest’ (Col. i, 26): and again of ‘publishing to the world the plan of the mystery, which had been kept hidden from the beginning of time in the all-creating mind of God’ (Eph. 3,6). What, then, are we to understand by this mystery, and in what does its revelation consist?