Make the mighty ocean
And the wondrous land,
and we doubtless speculate as to whether the sand grain and the water drop are not likewise divisible into smaller portions, and whether these smaller portions differ in quality from the larger. And so in the youth of science we find some philosophers maintaining the infinite divisibility of matter, and on the other hand the school founded by Leukippos and Demokritos, to whom we owe the conception and the word atom, the indivisible (or at least never divided) particle which forms the ultimate structure of matter. In these atoms, their ceaseless motion and their various groupings, is to be found the interpretation of the manifold phenomena of nature.
Both of these schools of thought have contributed to modern science. From the former we obtain the conception of a continuous medium which has developed into the theory of the all-pervading ether. From this school too we received the doctrine of the limited number of elementary substances from which all things are formed; a number which has grown from the four of Empedokles—earth, air, fire, water—through many vicissitudes into the eighty or so of the present day. But to the opposing school we owe a far greater debt, a debt which we can not lightly repudiate with Clifford by saying "The atomic theory of Demokritos was—no more than a guess—which was more near the right thing than the others." The atomic theory is much more than a guess. Incorporated into the system of Epikuros, and expounded in the marvelous poem of the Roman Lucretius, it forms a well-reasoned and well-balanced system of thought which it is true lacked in definiteness but was not without marked success in furnishing a framework on which to erect an image of nature. So successful was it that after two millenniums it has suffered little modification. As an illustration let us compare the atom of Lucretius with that of Newton.
These are the words of the Roman poet:
The atoms are of solid singleness, and, compact of smallest parts are closely-coherent—not compounded from a combination of these parts but strong in their everlasting singleness; from these Nature allows nothing to be broken off or diminished; . . . very different are they in their forms; varied by manifold shapes.[1]
While the description by Newton is as follows:
It seems probable that God in the beginning form'd Matter in solid, massy, hard, impenetrable, moveable Particles, of such Sizes and Figures, and with such other Properties. . . as most conduced to the End for which he form'd them; and that these primitive Particles being Solids, are incomparably harder than any porous Bodies compounded of them; even so very hard, as never to wear or break in pieces.[2]
A comparison of these passages shows how the two conceptions are
