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.

 In this verse we meet the conception of Antichrist. Antichrist is a word which occurs only in John's letters in the New Testament ( 1 John 2:22; 1 John 4:3; 2 John 1:7); but it is the expression of an idea which is as old as religion itself. 