Geologists distinguish three great epochs in the organic history of the earth, as far as we can read it in the monuments of the science of fossils--the primary, secondary, and tertiary epochs. According to a recent calculation, the first occupied at least thirty-four million, the second eleven million, and the third three million years. The history of the family of vertebrates, from which our own race has sprung, unfolds clearly before our eyes during this long period. Three different stages in the evolution of the vertebrate correspond to the three epochs; the _fishes_ characterized the primary (palæozoic) age, the _reptiles_ the secondary (mesozoic), and the _mammals_ the tertiary (cænozoic). Of the three groups the fishes rank lowest in organization, the reptiles come next, and the mammals take the highest place. We find, on nearer examination of the history of the three classes, that their various orders and families also advanced progressively during the three epochs towards a higher stage of perfection. May we consider this progressive development as the outcome of a conscious design or a moral order of the universe? Certainly not. The theory of selection teaches us that this organic progress, like the earlier organic differentiation, is an inevitable consequence of the struggle for existence. Thousands of beautiful and remarkable species of animals and plants have perished during those forty-eight million years, to give place to stronger competitors, and the victors in this struggle for life were not always the noblest or most perfect forms in a moral sense. It has been just the same with the history of humanity. The splendid civilization of classical antiquity perished because Christianity, with its faith in a loving God and its hope of a better life beyond the grave, gave a fresh, strong impetus to the soaring human mind. The Papal Church quickly degenerated into a pitiful caricature of real Christianity, and ruthlessly scattered the treasures of knowledge which the Hellenic philosophy had gathered; it gained the dominion of the world through the ignorance of the credulous masses. In time the Reformation broke the chains of this mental slavery, and assisted reason to secure its right once more. But in the new, as in the older, period the great struggle for existence went on in its eternal fluctuation, with no trace of a moral order.