social conditions among which they lived, found themselves unable to find truth readily, and reached the conclusion that each man is the measure of truth, that there are no universal criteria, or valid standards. The third stage begins with Socrates, who sought for a common principle of truth and justice in the midst of divergences, and this critical movement, continued by Plato and Aristotle, led to conceptions of unity once more. Now the social philosophy which goes with the first stage is relatively undefined. It is for the most part content with the existing order, recognizes a supernatural basis for it, and raises few questions. The social philosophy of the second period is intensely individualistic. In the third stage, the emphasis upon social solidarity and upon a unified, organic conception of society, a society which is paramount to individual interests and rights, comes to the fore again. The extreme poles of thought are, on the one hand, an individualism which leaves scant room for any very significant social relations whatsoever, and, on the other hand, a socialism--like that of the _Republic_--which swallows up the individual. The compromise view, expressed in the Aristotelian doctrine of the relation between "form" and "matter," applied to the social problem, finds the individual very real, to be sure, but still real only in his social relationships. Individual activities are facts, but social activity is more than a mere sum of individual activities. Society and the individual are alike abstractions, if viewed separately. The mediaeval conflict over realism and nominalism really derives its interest from the practical social issues involved, for the reality of the Church, as more than a mere aggregate of its members, and the validity of Christian doctrine, as more than the sum of individual beliefs, are at stake.