ly perish.' The
veritable existences in nature are the Atoms, which are too minute to
be discernible by the senses, but which nevertheless have a definite
size, and cannot further be divided. They have also a definite weight
and form, but no qualities other than these. There is an infinity of
empty space; this Epicurus proves on abstract grounds, practically
because a limit to space is unthinkable. It follows that there must be
an infinite number of the atoms, otherwise they would disperse
throughout the infinite void and disappear. There is a limit, however,
to the number of varieties among the atoms in respect of form, size,
and weight. The existence of the void space is proved by the fact that
motion takes place, to which he adds the argument that it necessarily
exists also to separate the atoms one from another. So far Epicurus
and Democritus are agreed.

To the Democritean doctrine, however, Epicurus made a curious addition,
to which he himself is said to have attached much importance. The
natural course (he said) for all bodies having weight is downwards in a
straight line. It struck Epicurus that this being so, the atoms would
all travel for ever in parallel lines, and those 'clashings and
interminglings' of {217} atoms out of which he conceived all visible
forms to be produced, could never occur. He therefore laid it down
that the atoms _deviated_ the least little bit from the straight, thus
making a world possible. And Epicurus considered that this supposed
deviation of the atoms not only made a world possible, but human
freedom also. In the deviation, without apparent cause, of the
descending atoms, the law of necessity was broken, and there was room
on the one hand for man's free will, on the other, for prayer to the
gods, and for hope of their interference on our behalf.

It may be worth while summarising the proofs which Lucretius in his
great poem, professedly following in the footsteps of Epicurus, adduces
for these various doctrines.

Epicurus' first dogma is, 'Nothing proceeds from nothing,' that is,
every material object has some matter previously existing exactly equal
in quantity to it, out of which it was made. To prove this Lucretius
appeals to the _order of nature_ as seen in the seasons, in the
phenomena of growth, in the fixed relations which exist between life
and its environment as regards what is helpful or harmful, in the
limitation of size and of faculties in the several spe