There was nothing then but the revelation of the spirit-of God that could make any of the Israelites understand and believe that he was their proper Messiah.
We learn this by the precepts that Jesus left. He observed that the people were looking outward, and assured them that the kingdom of God cometh not with outward observation; and for this reason, that it was only to be known in man.
Then, certainly, to be a Christian is to love God above all, and our neighbour as ourselves.