In this sentence, then, Thomas of Aquin was proclaiming the doctrine of the indestructibility of matter. It was not until well on in the nineteenth century that the chemists and physicists of modern times realized the truth of this great principle. The chemists had seen matter change its form in many ways, had seen it disappear apparently in the smoke of fire or evaporate under the influence of heat, but investigation proved that if care were taken in the collection of the gases that came off under these circumstances, of the ashes of combustion and of the residue of evaporation, all the original material that had been contained in the supposedly disappearing substance could be recovered or at least completely accounted for. The physicists on their part had realized this same truth and finally there came the definite enunciation of the absolute indestructibility of matter. St. Thomas' conclusion "Nothing at all will ever be reduced to nothingness" had anticipated this doctrine by nearly seven centuries. What happened in the Nineteenth Century was that there came an experimental demonstration of the truth of the principle. The principle itself, however, had been reached long before by the human mind by speculative processes quite as inerrable in their way as the more modern method of investigation.
When St. Thomas used the aphorism "Nothing at all will ever be reduced to nothingness" there was another signification that he attached to the words quite as clearly as that by which they expressed the indestructibility of matter. For him Nihil or nothing meant neither matter nor form, that is, neither the material substance nor the energy which is contained in it. He meant then, that no energy would ever be destroyed as well as no matter would ever be annihilated. He was teaching the conservation of energy as well as the indestructibility of matter. Here once more the experimental demonstration of the doctrine was delayed for over six centuries and a half. The truth itself, however, had been reached by this medieval master-mind and was the subject of his teaching to the university students in Paris in the Thirteenth Century. These examples should, I think, serve to illustrate that the minds of medieval students were occupied with practically the same questions as those which are now taught to the university students of our day. There are, however, some even more striking anticipations of modern teaching that will serve to demonstrate this community of educational interests in spite of seven centuries of time separation.
In recent years we have come to realize that matter is not the manifold material we were accustomed to think it when we accepted the hypothesis that there were some seventy odd different kinds of atoms, each one absolutely independent of any other and representing an ultimate term in science. The atomic theory from this standpoint has proved to be only a working hypothesis that was useful for a time, but that our physicists are now agreed must not be considered as something absolute. Radium has been observed changing into helium and the relations of atoms to one another as they are now known, make it almost certain that all of them have an underlying sub-stratum the same in all, but differentiated by the dynamic energies with which matter in its different forms is gifted. Sir Oliver Lodge has stated this theory of the constitution of matter very clearly in recent years, and in doing so has only been voicing the practically universal sentiment of those who have been following the latest developments in the physical sciences. Strange as it may appear, this was exactly the teaching of Aquinas and the schoolmen with regard to the constitution of matter. They said that the two constituting principles of matter were prime matter and form. By prime matter they meant the material sub-stratum the same in all material things. By form they meant the special dynamic energy which, entering into prime matter, causes it to act differently from other kinds and gives it all the particular qualities by which we recognize it. This theory was not original with them, having been adopted from Aristotle, but it was very clearly set forth, profoundly discussed, and amply illustrated by the schoolmen. In its development this theory was made to be of the greatest help in the explanation of many other difficulties with regard to living as well as non-living things in their hands. The theory has its difficulties, but they are less than those of any other theory of the constitution of matter, and it has been accepted by more philosophic thinkers since the Thirteenth Century than any other doctrine of similar nature. It may be said that it was reached only by deduction and not by experimental observation. Such an expression, however, instead of being really an objection is rather a demonstration of the fact that great truths may be reached by deduction yet only demonstrated by inductive methods many centuries later.
Of course it may well be said even after all these communities of interest between the medieval and the modern teaching of the general principles of science has been pointed out, that the universities of the Middle Ages did not present the subjects under discussion in a practical way, and their teaching was not likely to lead to directly beneficial results in applied science. It might well he responded to this, that it is not the function of a university to teach applications of science but only the great principles, the broad generalizations that underlie scientific thinking, leaving details to be filled in in whatever form of practical work the man may take up. Very few of those, however, who talk about the purely speculative character of medieval teaching have manifestly ever made it their business to know anything about the actual facts of old-time university teaching by definite knowledge, but have rather allowed themselves to be guided by speculation and by inadequate second-hand authorities, whose dicta they have never taken the trouble to substantiate by a glance at contemporary authorities on medieval matters.
It will be interesting to quote for the information of such men, the opinion of the greatest of medieval scientists with regard to the reason why men do not obtain real knowledge more rapidly than would seem ought to be the case, from the amount of work which they have devoted to obtaining it. Roger Bacon, summing up for Pope Clement the body of doctrine that he was teaching at the University of Oxford in the Thirteenth Century, starts out with the principle that there are four grounds of human ignorance. "These are first, trust in inadequate authority; second, the force of custom which leads men to accept too unquestioningly what has been accepted before their time; third, the placing of confidence in the opinion of the inexperienced; and fourth, the hiding of one's own ignorance with the parade of a superficial wisdom." Surely no one will ever be able to improve on these four grounds for human ignorance, and they continue to be as important in the twentieth century as they were in the Thirteenth. They could only have emanated from an eminently practical mind, accustomed to test by observation and by careful searching of authorities, every proposition that came to him. Professor Henry Morley, Professor of English Literature at University College, London, says of these grounds for ignorance of Roger Bacon, in his English Writers, Volume III, page 321: "No part of that ground has yet been cut away from beneath the feet of students, although six centuries ago the Oxford friar clearly pointed out its character. We still make sheep walks of second, third, and fourth and fiftieth-hand references to authority; still we are the slaves of habit; still we are found following too frequently the untaught crowd; still we flinch from the righteous and wholesome phrase, 'I do not know'; and acquiesce actively in the opinion of others that we know what we appear to know. Substitute honest research, original and independent thought, strict truth in the comparison of only what we really know with what is really known by others, and the strong redoubt of ignorance has fallen."
The number of things which Roger Bacon succeeded in discovering by the application of the principle of testing everything by personal observation, is almost incredible to a modern student of science and of education who has known nothing before of the progress in science made by this wonderful man. He has been sometimes declared to be the discoverer of gunpowder, but this is a mistake since it was known many years before