The only question now agitated is, whether the author of nature has formed primordial parts unsusceptible of division, or if all is continually dividing and changing into other elements. The first system seems to account for everything, and the second, hitherto at least, for nothing.
If the first elements of things were not indestructible one element might at last swallow up all the rest, and change them into its own substance. Hence, perhaps it was that Empedocles imagined that everything came from fire, and would be destroyed by fire.
This question of atoms involves another, that of the divisibility of matter ad infinitum. The word atom signifies without parts—not to be divided. You divide it in thought, for if you were to divide it in reality it would no longer be an atom.
You may divide a grain of gold into eighteen millions of visible parts; a grain of copper dissolved in spirit of sal ammoniac has exhibited upwards of twenty-two thousand parts; but when you have arrived at the last element the atom escapes the microscope, and you can divide no further except in imagination.
The infinite divisibility of atoms is like some propositions in geometry. You may pass an infinity of curves between a circle and its tangent, supposing the circle and the tangent to be lines without breadth; but there are no such lines in nature.
You likewise establish that asymptotes will approach one another without ever meeting; but it is under the supposition that they are lines having length without breadth—things which have only a speculative existence.
So, also, we represent unity by a line, and divide this line and this unity into as many fractions as you please; but this infinity of fractions will never be any other than our unity and our line.
It is not strictly demonstrated that atoms are indivisible, but it appears that they are not divided by the laws of nature.