=2. Coöperation in War.=--War and the blood feud, however divisive between groups, were none the less potent as uniting factors within the several groups. The members must not only unite or be wiped out, when the actual contest was on, but the whole scheme of mutual help in defense or in avenging injuries and insults made constant demand upon fellow feeling, and sacrifice for the good of all. To gain more land for the group, to acquire booty for the group, to revenge a slight done to some member of the group, were constant causes for war. Now although any individual might be the gainer, yet the chances were that he would himself suffer even though the group should win. In the case of blood revenge particularly, most of the group were not individually interested. Their resentment was a "sympathetic resentment," and one author has regarded this as perhaps the most fundamental of the sources of moral emotion. It was because the tribal blood had been shed, or the women of the clan insulted, that the group as a whole reacted, and in the clash of battle with opposing groups, was closer knit together. "Ally thyself with whom thou wilt in peace, yet know In war must every man be foe who is not kin." "Comrades in arms" by the very act of fighting together have a common cause, and by the mutual help and protection given and received become, for the time at least, one in will and one in heart. Ulysses counsels Agamemnon to marshal his Greeks, clan by clan and "brotherhood (phratry) by brotherhood," that thus brother may support and stimulate brother more effectively; but the effect is reciprocal, and it is indeed very probable that the unity of blood which is believed to be the tie binding together the members of the group, is often an afterthought or pious fiction designed to account for the unity which was really due originally to the stress of common struggle. =3. Art as Socializing Agency.=--Coöperation and sympathy are fostered by the activities of art. Some of these activities are spontaneous, but most of them serve some definite social end and are frequently organized for the definite purpose of increasing the unity and sympathy of the group. The hunting dance or the war dance represents, in dramatic form, all the processes of the hunt or fight, but it would be a mistake to suppose that this takes place purely for dramatic purposes. The dance and celebration after the chase or battle may give to the whole tribe the opportunity to repeat in vivid imagination the triumphs of the successful hunter or warrior, and thus to feel the thrill of victory and exult in common over the fallen prey. The dance which takes place before the event is designed to give magical power to the hunter or warrior. Every detail is performed with the most exact care and the whole tribe is thus enabled to share in the work of preparation.