The open and inquiring attitude of mind toward the truths of nature is supposed usually to be utterly at variance with the intellectual temper of the Middle Ages. We have heard so much about the submission to authority and the cultivation of tradition on the part of medieval scholars that we forget entirely how much they accomplished in adding to human knowledge, and though they had their limitations of conservatism, they were no more old fogies clinging to old-fashioned ruts than are the older men of each successive generation down even to our own time, in the minds of their younger colleagues. It might seem to be difficult to substantiate such a declaration. It may appear to be a paradox to talk thus. It is not hard to show good reasons for it, and far from being a far-fetched attempt to bolster up an opinion more favorable to the Middle Ages, it is really a very simple expression of what the history of these generations shows that they actually tried to accomplish. Roger Bacon must not be thought to be alone in this. On the contrary, he was only a leader with many followers. Even before his time, however, these ideas as to the necessity for observation had been very forcibly expressed by many, and by no one more than Roger's distinguished teacher, Albertus Magnus, whose name is now becoming familiar to scholars as Albert the Great. Albert's great pupil, Roger Bacon, is rightly looked upon as the true father of inductive science, an honor that history has unfortunately taken from him to confer {295} it undeservedly on his namesake of four centuries later; but the teaching out of which Roger Bacon was to develop the principles of experimental science can be found in many places in the master's writings. In Albert's tenth book, wherein 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 give certainty"--_experimentum solum certificat in talibus_. "Such an expression," says his biographer, "which might have proceeded from the pen of (Francis) Bacon, argues in itself a prodigious scientific progress, and shows that the medieval friar was on the track so successfully pursued by modern natural philosophy. He had fairly shaken off the shackles which had hitherto tied up discovery, and was the slave neither of Pliny nor of Aristotle."