FOR many thousands of years man has believed in and sought for the impossible. In chemistry he has searched for a universal solvent, for some way in which to change the baser metals into gold. Even Lord Bacon was a believer in this absurdity. Thousands of men, during many centuries, in thousands of ways, sought to change the nature of lead and iron so that they might be transformed to gold. They had no conception of the real nature of things. They supposed that they had originally been created by a kind of magic, and could by the same kind of magic be changed into something else. They were all believers in the supernatural. So, in mechanics, men sought for the impossible. They were believers in perpetual motion and they tried to make machines that would through a combination of levers furnish the force that propelled them. Thousands of ingenious men wasted their lives in the vain effort to produce machines that would in some wonderful way create a force. They did not know that force is eternal, that it can neither be created nor destroyed. They did not know that a machine having perpetual motion would necessarily be a universe within itself, or independent of this, and in which the force called friction would be necessarily changed, without loss, into the force that propelled,--the machine itself causing or creating the original force that put it in motion. And yet in spite of all the absurdities involved, for many centuries men, regarded by their fellows as intelligent and learned, tried to discover the great principle of "perpetual motion." Our ancestors studied the stars because in them they thought it possible to learn the fate of nations, the life and destiny of the individual. Eclipses, wandering comets, the relations of certain stars were the forerunners or causes of prosperity or disaster, of the downfall or upbuilding of kingdoms. Astrology was believed to be a science, and those who studied the stars were consulted by warriors, statesmen and kings. The account of the star that led the wise men of the East to the infant Christ was written by a believer in astrology. It would be hard to overstate the time and talent wasted in the study of this so-called science. The men who believed in astrology thought that they lived in a supernatural world--a world in which causes and effects had no necessary connection with each other--in which all events were the result of magic and necromancy. Even now, at the close of the nineteenth century, there are hundreds and hundreds of men who make their living by casting the horoscopes of idiots and imbeciles. The "perpetual motion" of the mechanic, the universal solvent of the chemist, the changing of lead into gold, the foretelling events by the relations of stars were all born of the same ignorance of nature that caused the theologian to imagine an uncaused cause as the cause of all causes and effects.