This era of heroes and gods is finally succeeded by a _fourth_ period. A national State and a national religion do not represent the permanent limits of human striving. National affiliations broaden into humanistic associations. Thus there begins a development in which we of the present still participate; it cannot, therefore, be referred to otherwise than as an age that is coming to be. We may speak merely of an advance _toward_ humanity, not of a development _of_ humanity. This advance, however, begins immediately with the fall of the barriers that divide peoples, particularly with regard to their religious views. For this reason, it is particularly the transcendence of the more restricted folk circle on the part of religions that constitutes one of the most significant events of mental history. The national religions--or, as they are generally, though misleadingly, called, the natural religions--of the great peoples of antiquity begin to pass beyond their original bounds and to become religions of humanity. There are three such world religions--Christianity, Islamism, and Buddhism--each of them adapted in character and history to a particular part of mankind. This appears most clearly in the contrast between Christianity and Buddhism, similar as they are in their endeavour to be world religions. The striving to become a world religion, however, is also a symptomatic mental phenomenon, paralleled externally by the extension of national States beyond the original limits set for them by the tribal unit. Corresponding to this expansion, we find those reciprocal influences of cultural peoples in economic life, as well as in custom, art, and science, which give to human society its composite character, representing a combination of national with universally human elements. Hellenism and the Roman Empire afford the first and, for Occidental mental development, the most important manifestations of these phenomena. How immense is the chasm between the secret barter of primitive man who steals out of the primeval forest by night and lays down his captured game to exchange it, unseen by his neighbours, for implements and objects of adornment, and the commerce of an age when fleets traverse the seas, and eventually ships course through the air, uniting the peoples of all parts of the world into one great commercial community! We cannot undertake to delineate all aspects of this development, for the latter includes the entire history of mankind. Our concern is merely to indicate the outstanding psychological factors fundamental to the progression of the later from that which was original, of the more perfect from the primitive, partly under the pressure of external conditions of life and partly as a result of man's own creative power.