In the universe there can be no progress in the sense of ascent, of motion from a worse to a better thing; the only thing in the universe, in Nature, which is comprehensible to the understanding and which experience, derived from sense perceptions, can establish, is evolution, an eternal, equable motion always on the same level; and human standards of value are not applicable to its regular, successive stages. One state is merged without a break in another, the simple becomes more manifold until a maximum of complexity is reached; thereupon what is intricate gradually falls to pieces, and the complicated is dissolved and returns to the simple; then, when this point is attained, the same course begins again, and so on for all eternity. Thus evolution in the universe is an endless succession of cyclic movements from the simple to the intricate and back to the simple; with a constant alternation from one point of each single circle to the other; with the most extreme, crushing uniformity in the totality of all cycles; with absolutely equal dignity of all the phases of the endless course as they develop one from the other; with a synchronism, inconceivable to man, of all forms of evolution in numberless circles revolving side by side within the infinite whole of the universe. But the concept of progress, which cannot be derived from the processes in the universe and has no sense when applied to them, becomes a reasonable one as soon as its validity is limited to the evolution of humanity. Here we no longer deal with conceptions of eternity and infinity. It is a question of temporal and spacial phenomena. The existence of man had a beginning. No doubt it will have an end. It appeared on earth latest at the commencement of the Quaternary geological period, but more probably towards the end of the Tertiary period. It must necessarily disappear when the earth, owing to cold and evaporation, becomes incapable of supporting life, a state of affairs which, according to our present knowledge of natural laws, must inevitably come to pass. A few million years are allotted to it in which to fulfil its destiny, certainly a short span of time compared with the eternity of the universe, but compared with the duration of individual and national life, with personal destinies and historical occurrences, an immeasurably vast prospect. Within the limits of its genesis, its being and its disappearance, it is in a constant state of evolution. It is impossible to deny this. Comparisons between the skulls found among remains of the paleolithic age and those of our times, between the state of the undeveloped tribes of central Africa and Australia and that of the peoples of Europe and America, between the beginnings of human speech and the present-day languages, between the thought, knowledge and abilities of former generations and ours--all these prove this incontrovertibly.