Morality, involving the modification of the conduct of the individual in view of the presence of others, is already highly developed in the tribal stage, since the exigencies of life have demanded the most rigorous regulation of behavior in order to secure the organization and the prowess essential to success against all comers. But the tribe is a unit in hostile coexistence with other similar units, and its morality stops within itself, and applies in no sense to strangers and outsiders. The North American Indians were theoretically at war with all with whom they had not concluded a treaty of peace. In Africa the traveler is safe and at an advantage if by a fiction (the rite of blood-brotherhood) he is made a member of the group; and similarly in Arabia and elsewhere. The old epics and histories are full of the praises of the man who is gentle within the group and furious without it. The earliest commandments doubtless did not originally apply to mankind at large. They meant, "Thou shalt not kill within the tribe," "Thou shalt not commit adultery within the tribe," etc. Cannibalism furnishes a most interesting example of the prohibition of a practice as applied to the members of the group, while extra-tribal cannibalism continued unabated. And within the tribe there is a continuance of this practice in the forms which do not interfere with the efficiency and cripple the activity of the group. That is, while cannibalism in general is prohibited, the eating of the decrepit, the aged, of invalids, of deformed children, and of malefactors is still practiced.[202]