equal interval will be of any more positive value-whether it will not have even less comparative interest than that which appertains to the scholasticism of the thirteenth.

Three men were the great teachers in the medieval universities at their prime. They have been read and studied with interest ever since. They wrote huge tomes, but men have pored over them in every generation. They were Albertus Albertus Magnus, the teacher of the other two, Thomas Aquinas and Roger Bacon. All three of them were together at the University of Paris shortly after the middle of the thirteenth century. Anyone who wants to know anything about the attitude of mind of the medieval universities, their professors and students, and of all the intellectual world of the time towards science and observation and experiment, should read the books of these men. Any other mode of getting at any knowledge of the real significance of the science of this time is mere pretence. These constitute the documents behind any scientific history of the development of science at this time.

It is extremely interesting to see the attitude of these men with regard to authority. In Albert's tenth book (of his "Summa "), in which he catalogues and describes all the trees, plants, and herbs known in his time, he observes: "All that is here set down is the result of our own experience, or has been borrowed from authors whom we know to have written what their personal experience has confirmed; for in these matters experience alone can be of certainty." In his impressive Latin phrase "experimentum solum certificat in talibus." With regard to the study of nature in general he was quite as emphatic. He was a theologian as well as a scientist, yet in his treatise on "The Heavens and the Earth" he declared that "in studying nature we have not to inquire how God the Creator may, as He freely wills, use His creatures to work miracles

and thereby show forth His power. We have rather to inquire what nature with its immanent causes can naturally bring to pass.

991

Just as striking quotations on this subject might be made from Roger Bacon. Indeed, Bacon was quite impatient with the scholars around him who talked over-much, did not observe enough, depended to excess on authority, and in general did as mediocre scholars always do, made much fuss on second-hand information-plus some filmy speculations of their own. Friar Bacon, however, had one great pupil whose work he thoroughly appreciated because it exhibited the opposite qualities. This was Petruswe have come to know him as Peregrinus—whose observations on magnetism have excited so much attention in recent years with the republications of his epistle on the subject. It is really a monograph on magnetism written in the thirteenth century. Roger Bacon's opinion of it and of its author furnishes us the best possible index of his attitude of mind towards observation and experiment in science.

I know of only one person who deserves praise for his work in experimental philosophy for he does not care for the discourses of men and their wordy warfare, but quietly and diligently pursues the works of wisdom. Therefore what others grope after blindly, as bats in the evening twilight, this man contemplates in their brilliancy because he is a master of experiment. Hence, he knows all of natural science whether pertaining to medicine and alchemy, or to matters celestial or terrestrial. He has worked diligently in the smelting of ores as also in the working of minerals; he is thoroughly acquainted with all sorts of arms and implements used in military service and in hunting, besides which he is skilled in agriculture and in the measurement of lands. It is impossible to write a useful or correct treatise in experimental philosophy without mentioning this man's name. Moreover, he pursues knowledge for its own sake; for if he wished to obtain royal favor, he could easily find sovereigns who would honor and enrich him.

Similar expressions might readily be quoted from Thomas Aquinas, but his works are so easy to secure

and his whole attitude of mind so well known, that it scarcely seems worth while taking space to do so. Aquinas is still studied very faithfully in many universities, and within the last few years one of his great text-books of philosophy has been replaced in the curriculum of Oxford University, in which it occupied a prominent position in the long ago, as a work that may be offered for examination in the department of philosophy. It is with regard to him particularly that there has been the greatest revulsion of feeling in recent years and a recognition of the fact that here was a great thinker familiar with all that was known in the physical sciences, and who had this knowledge constantly in his mind when he drew his conclusions with regard to philosophical and theological questions.

It used to be the fashion to make little of the medieval scholars for the high estimation in which they held Aristotle. Occasionally even yet one hears narrowly educated men, I am sorry to say much more frequently scientific specialists than others, talk deprecatingly of this ardent devotion to Aristotle. No one who knows anything about Aristotle ever indulges in such an exhibition of ignorance of the realities of the history of philosophy and science. To know Aristotle well is to think of him as probably possessed of the greatest human mind that ever existed. We do not need to go back to the Middle Ages to be confirmed in that opinion. Modern scientists who know their science well, but who also know Aristotle well, and who are ardent worshippers at his shrine, are not hard to find. Romanes, the great English biologist of the end of the nineteenth century, said: "It appears to me that there can be no question that Aristotle stands forth not only as the greatest figure in antiquity but as the greatest intellect that has ever appeared upon this earth."

mation of Aristotle they displayed the finest possible critical judgment. On the contrary, the generations who made much of the opportunity to minimize medieval scholarship because of its worship at the shrine of Aristotle, must themselves fall under the suspicion at least of either not knowing Aristotle or of not thinking deeply about the subjects with regard to which he wrote. For in all the world's history the rule has been that whenever men have thought deeply about a subject and know what Aristotle has written with regard to that subject, they have the liveliest admiration for the great Greek thinker. This is true for philosophy, logic, metaphysics, politics, ethics, dramatics, but it is also quite as true for physical science. He lacked our knowledge, though not nearly to the degree that is usually thought, and he had a marvellous accumulation of information, but he had a breadth of view and a thoroughness of appreciation with a power of penetration that make his opinions worth while knowing even on scientific subjects in our enlightened age.

As for the supposed swearing by Aristotle, in the sense of literally accepting his opinions without daring to examine them critically, which is so constantly asserted to have been the habit of the medieval scholars and teachers, it is extremely difficult in the light of the expressions which we have from them, to understand how this false impression arose. Aristotle they thoroughly respected. They constantly referred to his works, but so has every thinking generation ever since. Whenever he had made a declaration they would not accept the contradiction of it without a good reason, but whenever they had good reasons, Aristotle's opinion was at once rejected without compunction. Albertus Magnus, for instance, said: "Whoever believes that Aristotle was a God must also believe that he never erred,

but if we believe that Aristotle was a man, then doubtless he was liable to err just as we are. 99 A number of direct contradictions of Aristotle we have from Albert. A well-known one is that with regard to Aristotle's assertion that lunar rainbows appeared only twice in fifty years. Albert declared that he himself had seen two in a single year.

Indeed, it seems very clear that the whole trend of thought among the great teachers of the time was away from the acceptance of scientific conclusions on authority unless there was good evidence for them available. They were quite as impatient as the scientists of our time with the constant putting forward of Aristotle as if that settled a scientific question. Roger Bacon wanted the Pope to forbid the study of Aristotle because his works were leading men astray from the study of science, his authority being looked upon as so great that men did not think for themselves but accepted his assertions. Smaller men are always prone to do this, and indeed it constitutes one of the difficulties in the way of advance in scientific knowledge at all times, as Roger Bacon himself pointed out.

These are the sort of expressions that are to be expected from Friar Bacon from what we know of other parts of his work. His " Opus Tertium" was written at the request of Pope Clement IV, because the Pope had heard many interesting accounts of what the great thirteenth-century teacher and experimenter was doing at the University of Oxford, and wished to learn for himself the details of his work. Bacon starts out with the principle that there are four grounds of human ignorance. These are, first, trust in inadequate authority; second, that force of custom which leads men to accept without properly questioning what has been accepted before their time; third, the placing of confidence in the assertions of the inexperienced; and fourth, the hiding of