the vertebrates were evolved from its earliest forms, the mammalia from vertebrates, the primary apes from mammalia, and lastly, through progressive evolution, man was brought into being towards the end of the tertiary period--all these propositions had already been recognised and stated in germ by the Greek thinker who lived during the first generation of Greek philosophy. The sum total of the progress made in twenty-five hundred years, that what was then surmised from, rather than disclosed by, an empiric consideration of some few facts, has now been demonstrated in detail by scientific observation. But these main propositions, which the modern scientist regards as his own gains, because he has had to win them afresh by his own toil from the errors of the ancient and mediæval world, are of no great significance when compared with the far greater residuum of questions that still remain unanswered. Du Bois-Raymond, as is well known, described these “world riddles” in the year 1880 as in part unsolved, in part insoluble. They are seven in number: (1) The nature of matter and force; (2) the origin of motion; (3) the first beginning of life; (4) the adaptation of nature to certain ends; (5) the rise of sensation and consciousness; (6) the origin of thought and speech; (7) freedom of will. It is easy to see that, compared with these fundamental questions, which may be summed up in the great question of all, “God and the world,” the whole sequence of cosmic research from Anaximander to Haeckel is merely of secondary importance. It is, as it were, the surface of the matter; and even if, with Goethe, we feel the inadequacy of the apothegm of Haller, the poet and naturalist, “Into the heart of nature no created spirit may penetrate,” yet we cannot but see that as yet we poor mortals are only nibbling at the rind, and that centuries more of labour are needed to penetrate its diamond hardness. Thus everything that has hitherto been achieved is, as it were, a mere prelude to the abstract presentment of cosmic principles, and consequently the rudimentary beginnings of study in this sphere are far less remote from its present condition than is the case in any other department of the intellectual activity of mankind. And hence, even at the present day, the consideration of Greek philosophy is not only the most interesting, but also by far the most directly profitable part of the study of antiquity. No man who has not thoroughly studied the systems of Democritus, Plato, and Aristotle can become a profound philosopher in our own time.