and the Sophists, although part of his philosophy was intended as an answer to Protagoras, his
fellow-townsman and the most eminent of the Sophists. Protagoras, when he visited Athens,
was received enthusiastically; Democritus, on the other hand, says: "I went to Athens, and no
one knew me." For a long time, his philosophy was ignored in Athens; "It is not clear," says
Burnet, "that Plato knew anything about Democritus.... Aristotle, on the other hand, knows
Democritus well; for he too was an Ionian from the North." * Plato never mentions him in the
Dialogues, but is said by Diogenes Laertius to have disliked him so much that he wished all his
books burnt. Heath esteems him highly as a mathematician. â€
The fundamental ideas of the common philosophy of Leucippus and Democritus were due to
the former, but as regards the working out it is hardly possible to disentangle them, nor is it, for
our purposes, important to make the attempt. Leucippus, if not Democritus, was led to atomism
in the attempt to mediate between monism and pluralism, as represented by Parmenides and
Empedocles respectively. Their point of view was remarkably like that of modern science, and
avoided most of the faults to which Greek speculation was prone. They believed that everything
is composed of atoms, which are physically, but not geometrically, indivisible; that between the
atoms there is empty space; that atoms are indestructible; that they always have been, and
always will be, in motion; that there are an infinite number of atoms, and even of kinds of
atoms, the differences being as regards shape and size. Aristotle ‡ asserts that, according to
the atomists, atoms also differ as regards heat, the spherical atoms, which compose fire, being
the hottest; and as regards weight, he quotes Democritus as saying "The more any indivisible
exceeds, the heavier it is." But the question whether atoms are originally possessed of weight in
the theories of the atomists is a controversial one.
The atoms were always in motion, but there is disagreement among commentators as to the
character of the original motion. Some, especially Zeller, hold that the atoms were thought to be
always falling, and that the heavier ones fell faster; they thus caught up the lighter. ones, there
were impacts, and the atoms were deflected like billiard
* From Thales to Plato, p. 193.â
€
Greek Mathematics, Vol. I, p. 176.â
€
¡On Generation and Corruption, 326.