pedocles traces of the doctrine that the qualities of things
depend on the position and arrangement of their particles, this idea
is not consistently developed. For Empedocles there are only four
ultimate kinds of matter, qualitatively distinguished. The
differential qualities of all other kinds of matter must, therefore,
be due to the mixing of these four elements. Thus the qualities of the
four elements are ultimate and underived, but all other qualities must
be founded upon the position and arrangement of particles of the four
elements. This is the beginning of the mechanical explanation of
quality. But to develop this theory fully and consistently, it should
be shown, not merely that some qualities are ultimate and some {88}
derived from position and arrangement of particles, but that all
quality whatever is founded upon position and arrangement. All
becoming is explained by Empedocles as the result of motion of
material particles. To bring this mechanical philosophy to its logical
conclusion, all qualitativeness of things must be explained in the
same way. Hence it was impossible that the philosophy of mechanism and
materialism should stand still in the position in which Empedocles
left it. It had to advance to the position of Atomism. The Atomists,
therefore, maintain the essential position of Empedocles, after
eliminating the inconsistencies which we have just noted. The
philosophy of Empedocles is therefore to be considered as merely
transitional in character.

First, the Atomists developed the theory of particles. According to
Leucippus and Democritus, if matter were divided far enough, we should
ultimately come to indivisible units. These indivisible units are
called atoms, and atoms are therefore the ultimate constituents of
matter. They are infinite in number, and are too small to be
perceptible to the senses. Empedocles had assumed four different kinds
of matter. But, for the Atomists, there is only one kind. All the
atoms are composed of exactly the same kind of matter. With certain
exceptions, which I will mention in a moment, they possess no quality.
They are entirely non-qualitative, the only differences between them
being differences of quantity. They differ in size, some being larger,
some smaller. And they likewise differ in shape. Since the ultimate
particles of things thus possess no quality, all the actual qualities
of objects must be due to the {89} arrangement and position of the
atoms. This is