When we take man as a member of a group we have the same principle in operation, even though the form of its expression undergoes alteration. To begin with, the mere fact of living in a group implies the growth of a certain restraint in one's relations to, and of reciprocity in dealing with, others. Men can no more live together without some amount of trust and confidence in each other, or without a crude sense of justice in their dealings with each other, than an individual man can maintain his life by eating deadly poisons. There must be a respect for the rights of others, of justice in dealing with others, and of confidence in associating with others, at least to the extent of not threatening the possibility of group life. There are rules in the game of social life that must be observed, and in its own defence society is bound to suppress those of its members who exhibit strong anti-social tendencies. No society can, for example, tolerate homicide as an admitted practice. There is, thus, from the earliest times, a certain form of elimination of the anti-social character which results in the gradual formation of an emotional and mental disposition that habitually and instinctively falls into line with the requirements of the social whole. To use an expression of Sir Leslie Stephen's, man as a member of the group becomes a cell in the social tissue, and his fitness to survive is dependent upon, positively, his readiness to perform such actions as the welfare of the group require, and, negatively, upon his refraining from doing those things that are inimical to social welfare.[23] Moreover, there is the additional fact that the group itself is, as a whole, brought into contact with other groups, and the survival of one group as against another is determined by the quality and the degree of cohesion of its units. From this point of view, participation in the life of the group means more than refraining from acts that are injurious to the group, it involves some degree of positive contribution to social welfare. [23] The question of what are the things that are essential to the welfare of the group, and the fact that individuals are often suppressed for doing what they believe is beneficial to the group, with the kindred fact that there may exist grave differences of opinion on the matter, does not alter the essential point, which is that there must exist sufficient conformity between conduct and group welfare to secure survival.