Although Vico’s important treatise was not known outside of Italy until a century and a half after it was originally published, it contained a statement of the factor which is basic to any sound co-operation theory of social progress. Vico was one of the first writers to describe the principle that all human groups have a common nature. His comparative studies of human institutions everywhere, led him always to the belief in the common mind of mankind, a concept which in recent years has been ably elaborated by D. G. Brinton. For this contribution Vico has been called “the father of sociology.” According to Vico, the fundamental social movement is a gradual unfolding or evolution of social institutions in response to the common needs of people. Society owes its development in part to the reflections of the wise, as the social contract theorists have said, but also to the human feelings even of the brutish. This natural sociability of man has furnished the chief basis for the rise and development of the spirit of co-operation. The natural sociability of human beings has led, more or less unconsciously on the part of man, to the establishment of necessary social relations and institutions. The purpose of social organization is to produce perfect human personalities. Vico outlined the evolutionary character of society according to the spiral theory, namely, that society does return upon itself but that, when it completes a cycle, it is upon a higher plane of co-operation than when the given cycle began. Vico also made religion a necessary principle of progress. Although in adjusting himself to the prevailing theological dogmas of his time, Vico committed serious scientific errors, he nevertheless is deserving of special credit for his emphasis upon the common nature and natural sociability of mankind. Hugo Grotius (1583–1645), the celebrated Dutch scholar, gave to social thought the international concept. He advanced the idea of the coming co-operation among the nations--nations which in his time were moved primarily by jealousy and hatred in their relations with one another. Grotius was the originator of a definite set of principles and laws for international co-operation. His work in this regard accentuated the importance of like-mindedness in matters of international polity. Spinoza, whose contributions regarding the concept of sovereignty have already been stated, declared that the instinct to acquire is naturally stronger than the tendency to share. Hence, man must be educated to perceive the advantages of co-operative living. When this appreciation occurs, when the advantages of co-operation become clear, then man will sublimate his egoistic and self-seeking desires to altruistic communal living. As man comes to understand, step by step, the values of co-operative conduct, he will overcome, degree by degree, his selfish impulses.