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.

 (b) The fact that the passage is kin to poetry makes us think twice before insisting that so literal a meaning must be given to the words and so cut and dried a classification be taken as intended. Literalism and poetry do not go comfortably hand in hand. 