"The secret of Christ" written about by Paul in the letter to the Colossians was unknown to the ancient prophets, and even to the twelve disciples of Christ. To Israel, Jesus was the Messiah Who would save the nation and make her the head of all the nations. Not even the twelve had any clue as to the scope—as to the height, breadth, and depth  of what the Son of God came to accomplish. This was a secret hidden from the eons, revealed only to and by Paul.