There is a very general tendency to deny that ideal forces have any practical power. But there have been several thinkers whose skepticism has an opposite direction. "We can not," they say, "attribute external reality to the sensations we feel." We need not wonder that this theory has failed to convince the unmetaphysical common-sense of people that a stone post is merely a stubborn thought, and that the bite of a dog is nothing but an acquaintance with a pugnacious, four-footed conception. When a man falls downstairs it is not easy to convince him that his thought simply tumbles along an inclined series of perceptions and comes to a conclusion that breaks his head; least of all, can you induce a man to believe that the scolding of his wife is nothing but the buzzing of his own waspish thoughts, and her too free use of his purse only the loss of some golden fancies from his memory. We are all safe against such idealism as Bishop Berkeley reasoned out so logically. Byron's refutation of it is neat and witty: "When Bishop Berkeley says there is no matter, It is no matter what Bishop Berkeley says." And yet, by more satisfactory evidence than that which the idealists propose, we are warned against confounding the conception of substance with matter, and confining it to things we can see and grasp. Science steps in and shows us that the physical system of things leans on spirit. We talk of the world of matter, but there is no such world. Everything about us is a mixture or marriage of matter and spirit. A world of matter--there would be no motion, no force, no form, no order, no beauty, in the universe as it now is; organization meets us at every step and wherever we look; organization implies spirit--something that rules, disposes, penetrates and vivifies matter. See what a sermon astronomy preaches as to the substantial power of invisible things. If the visible universe is so stupendous, what shall we think of the unseen force and vitality in whose arms all its splendors rest? It is no gigantic Atlas, as the Greeks fancied, that upholds the celestial sphere; all the constellations are kept from falling by an impalpable energy that uses no muscles and no masonry. The ancient mathematician, Archimedes, once said, "Give me a foot of ground outside the globe to stand upon, and I will make a lever that will lift the world." The invisible lever of gravitation, however, without any fulcrum or purchase, does lift the globe, and makes it waltz, too, with its blonde lunar partner, twelve hundred miles a minute to the music of the sun--ay, and heaves sun and systems and Milky Way in majestic cotillions on its ethereal floor.