If we trace, however briefly, the gradual development of knowledge and
speculation on this subject, we shall perhaps appreciate more fully the
advance we have really made during the present century.
The first speculations on the nature and source of the phenomena of the
universe, of which we have any knowledge, are those of the early Greek
philosophers, such as Thales, Anaximander, Anaxagoras, and Empedocles;
but as the more important of their teachings are embodied, with some
approach to system and with much acuteness of reasoning, in the great
poem of the Latin author Lucretius, “On the Nature of Things,” it will
be sufficient to give a sketch of his main conclusions, making use
of the excellent prose translation by Mr. H. A. J. Munro, of Trinity
College, Cambridge.
Lucretius had a very clear idea of the indestructibility of matter.
He argues that things cannot have come out of nothing, and he says:
“A thing never returns to nothing, but all things, after disruption,
go back into the first bodies of matter.” He then argues that, as
the actual processes of growth, decay, and other natural changes are
imperceptible to us, therefore “Nature works by unseen bodies.” He
justly claims great importance for the demonstration of the fact that
in all matter whatever, however solid and hard it may be, there are
vacancies, or, as he expresses it, “Mixed up in all things there is
void or empty space.” He thus anticipated the modern doctrine that the
molecules of matter do not come into actual contact. He then defines
atoms thus: “First bodies are solid and without void”; and as nothing
can be produced from nothing, he concludes that these first bodies
(atoms or molecules) must be everlasting, and that they supply matter
for the reproduction of all things.
He then goes on to prove that these “first beginnings are of solid
singleness, not formed of parts, but strong in everlasting singleness.”
He further proves that these “first beginnings” (atoms) cannot be
infinitely small, and also that the universe cannot be limited—that
it is infinite. He thus anticipated the main ideas as to atoms and the
universe which have been held by most materialistic thinkers down to
our own times.
Lucretius was an absolute materialist, for though he did not deny the
existence of the gods he refused them any share in the construction of
the universe, which, he again and again urges, arose by chance, after
infinite time, by the random motions and collisions and entanglements
of the infinity of atoms. He assumes some forces analogous to
gravitation and the molecular motions of gases in the following
passage: “For the first beginnings of things move first of themselves;
next these bodies which form a small aggregate and come nearest, so
to say, to the powers of the first beginnings are impelled and set in
movement by the unseen strokes of these first bodies, and they next in
turn stir up other bodies which are a little larger.”
He also anticipated Galileo as to the equal speed of all falling bodies
when not checked by the air in the following precise statement: “For
whenever bodies fall through water and thin air they must quicken their
descents in proportion to their weights, because the body of water and
subtle nature of air cannot retard everything to an equal degree; on
the other hand, empty void cannot offer resistance to anything in any
direction at any time, but must continually give way; and for this
reason all things must be moved and borne along with equal velocity,
though of unequal weights, through the unresisting void.”
This is a wonderfully accurate general statement of the equal rate
of motion of all kinds of matter under the same forces; and when we
consider that there is no indication of any experimental basis for this
conclusion, and that nothing equivalent to our sciences of physics or
chemistry existed, we are amazed at the general correctness of many
of his views, derived solely by a process of reasoning from the most
obvious phenomena of nature. He argues that, given infinite matter and
space and inherent motion, “things must go on and be completed,” and
his general conclusion is thus expressed: “If you will apprehend and
keep in mind these things, nature, free at once and rid of her haughty
lords, is seen to do all things spontaneously of herself without the
meddling of the gods.”
It is when he attempts to deal with the origin of living organisms
that the absence of all knowledge of chemistry, physiology, and
histology renders his task impossible and leads him into what seem to
us the wildest absurdities. He has an elaborate but very unconvincing
argument that sensation can arise out of atoms which have no sensation;
and, taking the appearance of worms, etc., in the earth and in putrid
matter as a proof that they are still actually produced _de novo_ in
it, he argues that at some remote epoch the now worn-out earth was more
fertile, and produced in like manner all kinds of animals. The first
human infants he supposes to have been formed at some very remote time
in the manner following: “For much heat and moisture would then abound
in the fields; and therefore wherever a suitable spot offered wombs
would grow, attached to the earth by roots; and when the warmth of the
infants, flying the wet and craving the air, had opened these in the
fulness of time, nature would turn to that spot the pores of the earth
and constrain it to yield from its opened veins a liquid most like to
milk. To the children the earth would furnish food, the heat raiment,
the grass a bed rich in abundance of soft down.... Wherefore, again and
again I say, the earth, with good title, has gotten and keeps the name
of mother, since she of herself gave birth to mankind, and at a time
nearly fixed shed forth every beast that ranges wildly over the great
mountains, and at the same time the fowls of the air with all their
varied shapes.”
The fact that this mode of origin commended itself to one of the
brightest intellects of the first century B. C., enlightened by the
best thought of the Grecian philosophers, may enable us the better to
appreciate the immense advance made by modern evolutionists.