To-day we are all familiar with the dictum that the maintenance of life is a question of adaptation to environment--a truth that is equally applicable to ideas and institutions. But the general truth admitted, there is next required a consideration of its application to the particular subject in hand, and in connection with our present topic some attention must be paid both to the nature of the organism and of the environment with which we are dealing. We then discover that not alone are we dealing with an organism which is extremely plastic in its nature, but that the environment may also vary within very wide limits. On the one side, and in relation to man, we may be dealing with an environment that is mainly physical in character, or it may be a combination of physical conditions and biological forces, or, yet again, it may be predominantly psychological in its nature. And, on the other hand, the reaction of the organism on the environment may vary from extreme feebleness to an almost overpowering determination. We may, indeed, anticipate our argument by saying that one of the chief features of human progress is the gradual subordination of the material environment to the psychologic powers of man. If, now, we contrast the environment of an uncivilized with that of a civilized people the difference is striking. The environment of an uncivilized race will consist of the immediate physical surroundings, the animals that are hunted for sport or killed for food, and a comparatively meagre stock of customs and traditions. The environment of a modern European will add to the physical surroundings an enormously enlarged mass of social traditions and customs, an extensive literature, contact with numerous other societies in various stages of culture, and relations, more or less obscure, to a vast literary and social past. The environment thus includes not merely the living, but also the dead. Roman law, Greek philosophy, Eastern religious ideas, etc., all affect the twentieth century European. It would require a lengthy essay to enumerate all the influences that dominate the life of a particular people of to-day, but enough has been said to illustrate the truth that we must use the term "environment" so as to include _all_ that affects the organism. And when this is done it soon becomes clear that by the very growth of humanity the influence of the physical portion of the environment becomes of relatively less importance with the progress of the race--it is the subordination of the physical environment that is the principal condition of the advance of civilization.