One or two examples will suffice, I think, to show very clearly that the students of the Thirteenth Century had presented to them practically the same problems with regard to matter, its origin and composition, as occupy the students of the present generation. For instance Thomas Aquinas usually known as St. Thomas, in a series of lectures given at the University of Paris toward the end of the third quarter of the Thirteenth Century, stated as the most important conclusion with regard to matter, that _"Nihil omnino in nihilum redigetur_,"' "Nothing at all will ever be reduced to nothingness." By this it was very evident from the context that he meant that matter would never be annihilated and could never be destroyed. It might be changed in various ways but it could never go back into the nothingness from which it had been taken by the creative act. Annihilation was pronounced as not being a part of the scheme of things as far as the human mind could hope to fathom its meaning. In this sentence, then, Thomas of Aquin was proclaiming the {39} 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.