detriment of the truth. In the degree in which the individual rather than reason "knew," conceit, error, and opinion were substituted for true knowledge. In Greek life, observation was acute and alert; and thinking was free almost to the point of irresponsible speculations. Accordingly the consequences of the theory were only such as were consequent upon the lack of an experimental method. Without such a method individuals could not engage in knowing, and be checked up by the results of the inquiries of others. Without such liability to test by others, the minds of men could not be intellectually responsible; results were to be accepted because of their aesthetic consistency, agreeable quality, or the prestige of their authors. In the barbarian period, individuals were in a still more humble attitude to truth; important knowledge was supposed to be divinely revealed, and nothing remained for the minds of individuals except to work it over after it had been received on authority. Aside from the more consciously philosophic aspects of these movements, it never occurs to any one to identify mind and the personal self wherever beliefs are transmitted by custom. In the medieval period there was a religious individualism. The deepest concern of life was the salvation of the individual soul. In the later Middle Ages, this latent individualism found conscious formulation in the nominalistic philosophies, which treated the structure of knowledge as something built up within the individual through his own acts, and mental states. With the rise of economic and political individualism after the sixteenth century, and with the development of Protestantism, the times were ripe for an emphasis upon the rights and duties of the individual in achieving knowledge for himself. This led to the view that knowledge is won wholly through personal and private experiences. As a consequence, mind, the source and possessor of knowledge, was thought of as wholly individual. Thus upon the educational side, we find educational reformers, like Montaigne, Bacon, Locke, henceforth vehemently denouncing all learning which is acquired on hearsay, and asserting that even if beliefs happen to be true, they do not constitute knowledge unless they have grown up in and been tested by personal experience. The reaction against authority in all spheres of life, and the intensity of the struggle, against great odds, for freedom of action and inquiry, led to such an emphasis upon personal observations and ideas as in effect to isolate mind, and set it apart from the world to be known.