to deduce general laws from observation. As we moderns see it,
such criticism is the highest possible praise. It is a criticism
that marks the distinction between the scientist who is also a
philosopher and the philosopher who has but a vague notion of
physical science. Plato seemed, indeed, to realize the value of
scientific investigation; he referred to the astronomical studies
of the Egyptians and Chaldeans, and spoke hopefully of the
results that might accrue were such studies to be taken up by
that Greek mind which, as he justly conceived, had the power to
vitalize and enrich all that it touched. But he told here of what
he would have others do, not of what he himself thought of doing.
His voice was prophetic, but it stimulated no worker of his own
time.

Plato himself had travelled widely. It is a familiar legend that
he lived for years in Egypt, endeavoring there to penetrate the
mysteries of Egyptian science. It is said even that the rudiments
of geometry which he acquired there influenced all his later
teachings. But be that as it may, the historian of science must
recognize in the founder of the Academy a moral teacher and
metaphysical dreamer and sociologist, but not, in the modern
acceptance of the term, a scientist. Those wider phases of
biological science which find their expression in metaphysics, in
ethics, in political economy, lie without our present scope; and
for the development of those subjects with which we are more
directly concerned, Plato, like his master, has a negative
significance.


ARISTOTLE (384-322 B.C.)

When we pass to that third great Athenian teacher, Aristotle, the
case is far different. Here was a man whose name was to be
received as almost a synonym for Greek science for more than a
thousand years after his death. All through the Middle Ages his
writings were to be accepted as virtually the last word regarding
the problems of nature. We shall see that his followers actually
preferred his mandate to the testimony of their own senses. We
shall see, further, that modern science progressed somewhat in
proportion as it overthrew the Aristotelian dogmas. But the
traditions of seventeen or eighteen centuries are not easily set
aside, and it is perhaps not too much to say that the name of
Aristotle stands, even in our own time, as vaguely representative
in the popular mind of all that was highest and best in the
science of antiquity. Yet, perhaps, it would not be going too far
to assert that something like a reversal of this judgment would
be nearer the truth. Aristotle did, indeed, bring together a
great mass of facts regarding animals in his work on natural
history, which, being preserved, has been deemed to entitle its
author to be called the "father of zoology." But there is no
reason to suppose that any considerable portion of this work
contained matter that was novel, or recorded observations that
were original with Aristotle; and the classifications there
outlined are at best but a vague foreshadowing of the elaboration
of the science. Such as it is, however, the natural history
stands to the credit of the Stagirite. He must be credited, too,
with a clear enunciation of one most important scientific
doctrine--namely, the doctrine of the spherical figure of the
earth. We have already seen that this theory originated with the
Pythagorean philosophers out in Italy. We have seen, too, that
the doctrine had not made its way in Attica in the time of
Anaxagoras. But in the intervening century it had gained wide
currency, else so essentially conservative a thinker as Aristotle
would scarcely have accepted it. He did accept it, however, and
gave the doctrine clearest and most precise expression. Here are
his words:[2]


"As to the figure of the earth it must necessarily be
spherical.... If it were not so, the eclipses of the moon would
not have such sections as they have. For in the configurations in
the course of a month the deficient part takes all different
shapes; it is straight, and concave, and convex; but in eclipses
it always has the line of divisions convex; wherefore, since the
moon is eclipsed in consequence of the interposition of the
earth, the periphery of the earth must be the cause of this by
having a spherical form. And again, from the appearance of the
stars it is clear, not only that the earth is round, but that its
size is not very large; for when we make a small removal to the
south or the north, the circle of the horizon becomes palpably
different, so that the stars overhead undergo a great change, and
are not the same to those that travel in the north and to the
south. For some stars are seen in Egypt or at Cyprus, but are not
seen in the countries to the north of these; and the stars that
in the north are visible while they make a complete circuit,
there undergo a setting. So that from this it is manifest, not
only that the form of the earth is round, but also that it is a
part of a not very large sphere; for otherwise the difference
would not be so obvious to persons making so small a change of
place. Wherefore we may judge that those persons who connect the
region in the neighborhood of the pillars of Hercules with that
towards India, and who assert that in this way the sea is one, do
not assert things very improbable. They confirm this conjecture
moreover by the elephants, which are said to be of the same
species towards each extreme; as if this circumstance was a
consequence of the conjunction of the extremes. The
mathematicians who try to calculate the measure of the
circumference, make it amount to four hundred thousand stadia;
whence we collect that the earth is not only spherical, but is
not large compared with the magnitude of the other stars."


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