They went out from us, but they didn't belong to us; for if they had belonged to us, they would have continued with us. But they left, that they might be revealed that none of them belong to us.

 Here was John's problem. In the Greek world he was faced with people who saw God as an intellectual exercise and who could say, "I know God" without being conscious of any ethical obligation whatever. In the Greek world he was faced with people who had had an emotional experience and who could say, "I am in God and God is in me," and who yet did not see God in terms of commandments at all. 