The conceptions of the ancients respecting the fixed stars were not less
clear than ours. Indeed, the opinions of the moderns on this subject
have been adopted within a century from those great masters, after
having been rejected during many ages. It would be reckoned almost an
absurdity at present, to doubt of those stars being suns like ours, each
respectively having planets of their own, revolving around them, and
forming various solar systems, more or less resembling ours. Philosophy,
at present, admits this theory, derived from the ancients, and founded
on the most solid reasonings of astronomical science. The elegant work
of Fontenelle, on the “Plurality of Worlds,” first rendered the
conception familiar to common minds.
This notion of a plurality of worlds was generally inculcated by the
Greek philosophers. Plutarch, after giving an account of it, says, that
“he was so far from finding fault with it, that he thought it highly
probable there had been, and were, like this of ours, an innumerable,
though not absolutely infinite, multitude of worlds; wherein, as well as
here, were land and water, invested by sky.”
Anaximenes was one of the first who taught, that “the stars were immense
masses of fire, around which certain terrestrial globes, imperceptible
to us, accomplished their periodic revolutions.” By these terrestrial
globes, turning round those masses of fire, he evidently meant planets,
such as ours, subordinate to their own sun, and forming a solar system.
Anaximenes agreed with Thales in this opinion, which passed from the
Ionic to the Italic sect; who held, that every star was a world,
containing in itself a sun and planets, all fixed in that immense space,
which they called ether.
Heraclides, and all the Pythagoreans likewise taught, that “every star
was a world, or solary system, having, like this of ours, its sun and
planets, invested with an atmosphere of air, and moving in the fluid
ether, by which they were sustained.” This opinion seems to have been of
still more ancient origin. There are traces of it in the verses of
Orpheus, who lived in the time of the Trojan war, and taught that there
was a plurality of worlds; a doctrine which Epicurus also deemed very
probable.
Origen treats amply of the opinion of Democritus, saying, that “he
taught, that there was an innumerable multitude of worlds, of unequal
size, and differing in the number of their planets; that some of them
were as large as ours, and placed at unequal distances; that some were
inhabited by animals, which he could not take upon him to describe; and
that some had neither animals, nor plants, nor any thing like what
appeared among us.” The philosophic genius of the illustrious ancient
discerned, that the different nature of those spheres necessarily
required inhabitants of different kinds.
This opinion of Democritus surprised Alexander into a sudden declaration
of his unbounded ambition. Ælian reports, that this young prince, upon
hearing Democritus’s doctrine of a plurality of worlds, burst into
tears, upon reflecting that he had not yet so much as conquered one of
them.
It appears, that Aristotle also held this opinion, as did likewise
Alcinoüs, the Platonist. It is also ascribed to Plotinus; who held
besides, that the earth, compared to the rest of the universe, was one
of the meanest globes in it.