Another man of genius, the German Kepler, worked out the mathematical laws which govern the movements of the planets. He made it clear that the planets revolve around sun in elliptical instead of circular orbits. Kepler's investigations afterwards led to the discovery of the principle of gravitation.
VESALIUS, 1514-1564 A.D., AND HARVEY, 1578-1657 A.D.
Two other scientists did epochal work in a field far removed from astronomy. Vesalius, a Fleming, who studied in Italian medical schools, gave to the world the first careful description of the human body based on actual dissection. He was thus the founder of human anatomy. Harvey, an Englishman, after observing living animals, announced the discovery of the circulation of the blood. He thereby founded human physiology.
THE SCIENTIFIC METHOD
Copernicus, Galileo, Kepler, Vesalius, Harvey, and their fellow workers built up the scientific method. In the Middle Ages students had mostly been satisfied to accept what Aristotle and other philosophers had said, without trying to prove their statements. [20] Kepler, for instance, was the first to disprove the Aristotelian idea that, as all perfect motion is circular, therefore the heavenly bodies must move in circular orbits. Similarly, the world had to wait many centuries before Harvey showed Aristotle's error in supposing that the blood arose in the liver, went thence to the heart, and by the veins was conducted over the body. The new scientific method rested on observation and experiment. Students learned at length to take nothing for granted, to set aside all authority, and to go straight to nature for their facts. As Lord Bacon, [21] one of Shakespeare's contemporaries and a severe critic of the old scholasticism, declared, "All depends on keeping the eye steadily fixed upon the facts of nature, and so receiving their images simply as they are, for God forbid that we should give out a dream of our own imagination for a pattern of the world." Modern science, to which we owe so much, is a product of the Renaissance.
217. THE ECONOMIC RENAISSANCE
AN ECONOMIC CHANGE
Thus far the Renaissance has been studied as an intellectual and artistic movement, which did much to liberate the human mind and brought the Middle Ages to an end in literature, in art, and in science. It is necessary, however, to consider the Renaissance era from another point of view. During this time an economic change of vast significance was taking place in rural life all over western Europe. We refer to the decline and ultimate extinction of medieval serfdom.
DECLINE OF SERFDOM
Serfdom imposed a burden only less heavy than the slavery which it had displaced. The serf, as has been shown, [22] might not leave the manor in which he was born, he might not sell his holdings of land, and, finally, he had to give up a large part of his time to work without pay for the lord of the manor. This system of forced labor was at once unprofitable to the lord and irksome to his serfs. After the revival of trade and industry in the twelfth and thirteenth centuries had brought more money into circulation, [23] the lord discovered how much better it was to hire men to work for him, as he needed them, instead of depending on serfs who shirked their tasks as far as possible. The latter, in turn, were glad to pay the lord a fixed sum for the use of land, since now they could devote themselves entirely to its cultivation. Both parties gained by an arrangement which converted the manorial lord into a landlord and the serf into a free tenant-farmer paying rent.