Gilbert Galileo and Harvey, Maxwell Hertz and Darwin have taught men not that the speculations of the schoolmen were over-bold, for they busied themselves with no speculations bolder or more transcendental than are our modern theories on matter, on inertia, on the ether, or on the origin of life, but that metaphysics by “intercalation of facts” shall become physics, that, in the words of Descartes, concepts, if “μετὰ τὰ φυσικά,” “talia sint tantum ut omnibus naturae phænomenis accurate respondeant,” and that notions great and small shall be subjected to strict verification, so far as such tests can be carried; not that men shall deny themselves the rapture of touching that various instrument they find within themselves, but that they shall endure the drudgery of learning to play it in harmony with the orchestra of nature; not that they shall desist from imagining, but that before proclaiming hypotheses they shall be compelled to the humble task of making an infinite number of little piles of facts. The art of experiment can grow only with the growth of science itself; instruments of precision are not provided till men feel the need of them. The experimental verification of concepts is no mere alternative path, no mere renunciation, but a new birth; a birth into a dull and vexatious discipline for the impatient Hegelian, whether of the thirteenth or of the twentieth century, who believes that, as mind is the product of evolution, and so the sum and store of nature, “in dem Gedanken selbst das Wahre ist zu suchen[75].” “Long fed on boundless hopes, O race of man, How angrily thou spurn’st all simpler fare.”