ment and the observation of Nature, he stood out as the champion of unfettered inquiry in a period of scientific stagnation, and he suffered persecution, banishment and imprisonment for his temerity. In popular esteem the memory of this champion of experimental science and advocate of positive knowledge has always been cherished; and after seven hundred years, in 1914, Oxford commemorated the birth of this-one of her greatest sons described by Humboldt as "the greatest apparition of the Middle Ages," by erecting a statue to him.

Two hundred years after Roger Bacon, appeared that prodigy of Nature, Leonardo da Vinci (1452-1519), whose curiosity was insatiable, and whose methods were to search out all things, to experiment and verify, to let his eyes test and his reason judge. Another Italian philosopher who saw that the appeal should be from authority to Nature and urged that all true knowledge came from data given by the senses, was Bernardino Telesio (1509-1588). Leonardo himself had the clearest ideas as to the scientific method of inquiry.

In treating any particular subject I would first of all make some experiments, because my design is first to refer to experiments and then to demonstrate why bodies are constrained to act in such a manner. This is the method we ought to follow in investigating the phenomena of Nature. Theory is the general, experiments are the soldiers. Experiment is the interpreter of the artifices of Nature. It is never wrong; but our judgment is sometimes deceived because we are expecting results which experiment refuses to give. We must consult experiment and vary the circumstances, till we have deduced general laws, for it alone can furnish us with them. Leonardo da Vinci.

Leonardo was by profession an engineer, but he was also sculptor, musician and poet, and his fresco representing the Last Supper places him among the most illustrious artists of the world. He investigated

thoroughly the laws relating to the movement of water and hydraulics generally, and anticipated many of the theories for which credit is often given to men of science who lived many years after him. Hallam, in his Introduction to the Literature of Europe, says that the discoveries which made the names of Galileo, Kepler and others famous, the system of Copernicus, and the theories of modern geologists, were anticipated by Leonardo within the compass of a few pages; not perhaps in the most precise language, or in the most conclusive reasoning, but so as to strike us with something like the awe of preternatural knowledge. In his work as an engineer he followed truly scientific methods. Those," he said, "who are infatuated by practice without science, are like the navigator who sails a ship without helm and compass; he never knows with certainty whither he goes. Practice must always be built upon theory. Study science first, then follow the practice which is born of science."

66

Bernard Palissy, the potter who sacrificed everything, even the furniture of his cottage, in the production of a glaze for earthenware, was also one of the earliest followers of the experimental method of studying other aspects of Nature. His life extended over nearly the whole of the sixteenth century, and his contributions to agriculture, chemistry, mineralogy and geology disturbed the schoolmen and provided a new foundation for science. He was the first to give a true explanation of the origin of springs, and like Leonardo da Vinci, he understood that fossils represented past forms of life and were not freaks of Nature or relics of the world before Noah's flood. Buffon said of him, about a century and a half later, "a simple potter of the end of the sixteenth century was the first to dare

to tell Paris and the doctors that marine fossils were true animal remains, were deposited in a sea in the place where they are now found, and were born of their respective animal parents. This he defied the Aristotelians to deny."

Palissy offended the alchemists and astrologers of his time, as well as the priests and philosophers, by his ridicule of cherished opinion regarding natural objects and phenomena; and he died in prison in consequence of his appeal to observation and experiment for the basis of every speculation. He was an apostle of the inductive method, and demonstrated its application to large audiences in Paris, during the three years which Francis Bacon spent there in his youth; it has indeed been suggested by Sir Clifford Allbutt that Bacon first derived his ideas of inductive philosophy from the collections and contentions of Palissy, whose observations and influence are, however, rarely mentioned in the history of scientific thought.

Dr. William Gilbert (1540-1603), of Colchester, known to most students of magnetism and electricity as the founder of these branches of science, also practised the experimental method of investigation before Francis Bacon wrote about it. He is, indeed, repeatedly mentioned by Bacon in the Novum Organum, and elsewhere he is praised both for his industry and his method, but censured for endeavouring to build a universal philosophy upon a narrow basis; and not without reason. Gilbert was largely indebted in his work on magnetism to the observations of Peter Peregrinus made three centuries earlier, and he was so dominated by the notion that magnets possessed some sort of soul or spirit that he should perhaps be considered as a sort of connecting link between medieval superstitions and the

modern spirit. He did, however, make better use of the experimental method than any natural philosopher who preceded him, and his work did much to break down the barrier raised by traditional belief against independent investigation.

In the discovery of secrets, and in the investigation of the hidden causes of things, clear proofs are afforded by trustworthy experiments rather than by probable guesses and opinions of ordinary professors and philosophers . . . To you alone, honest and true men of science, who seek knowledge, not from books only, but also from things themselves, do I address these magnetic principles and this new sort of philosophy. If any disagree with my opinion, let them at least take note of the experiments and discoveries which have been worked out and demonstrated by me, with many pains and vigils and expenses. Let them rejoice in these, and employ them to better use if they are able. W. Gilbert.

The ancients used only two methods of investigation -the philosophical and the mathematical; the third method, by experiment, was put into deliberate practice by Palissy, Gilbert and Galileo. By offering experimental evidence against what was believed to be the teachings of Aristotle, Galileo established the modern experimental method of inquiry in Nature. The authority of Aristotle as the arch-priest of natural science had been questioned before the time of Galileo, but no attempt had been made to confound it with truths secured by direct appeal to Nature. The high regard in which Galileo held the facts obtained by experiment, in comparison with the conclusions of peripatetic philosophy, is reflected in a letter written by him in 1615:

I would entreat these wise and prudent fathers to consider diligently the difference between opinionative and demonstrative doctrines, to the end that they may assure themselves that it is not in the power of professors of demonstrative sciences to change their opinions at pleasure. Galileo,

Francis Bacon is sometimes called the Father of Experimental Philosophy, but it may be doubted whether he merits the title; indeed, he disregarded in his own works the very principles of scientific investigation expounded by them. What Bacon did was to form into a system the method of investigation which consists in asking questions of Nature herself, of making observations with great care, carefully arranging them, and cautiously arriving at conclusions from them. Aristotle had long before insisted upon the collection of facts, and urged that we must "first classify them, bring particular facts under general heads and coordinate them into theories." He collected so-called "facts" by hundreds, and proceeded to speculate upon them as if they were unalterable truths, whereas in many cases they were merely old women's tales or other hearsay evidence. His method was a logical machine which could produce reasonable results when provided with sound material to work upon, but not otherwise. Aristotle and the school of thought he dominated for nearly two thousand years, knew nothing of the experimental method of inquiry; and by proclaiming that our only hope is in the regeneration of the sciences by regularly raising them on the foundation of experiBacon became the apostle of a new school of philosophy, though not the founder of it.

66

ence

Bacon's influence in establishing this inductive process of inquiry is often over-estimated, and he owes his prominence to the fact that his works appeared at the right psychological moment, when the age was ripe to receive a new philosophy. As we have seen, three centuries before the time of Francis Bacon, the main doctrines he promulgated had been proclaimed by Roger Bacon, and not only