ns of what is most modern in science be found than in some
of these considerations of basic principles in the physical sciences.

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, as is very evident from the context, he meant to say 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 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 {314} 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's 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 mea