who taught mathematics in the schools. And
I found first, indeed, in Cicero, that Niceta perceived that the Earth
moved; and afterward in Plutarch I found that some others were of this
opinion, whose words I have seen fit to quote here, that they may be
accessible to all:--

"Some maintain that the Earth is stationary, but Philolaus the
Pythagorean says that it revolves in a circle about the fire of the
ecliptic, like the sun and moon. Heraklides of Pontus and Ekphantus
the Pythagorean make the Earth move, not changing its position,
however, confined in its falling and rising around its own center in
the manner of a wheel."

Taking this as a starting point, I began to consider the mobility of
the Earth; and although the idea seemed absurd, yet because I knew
that the liberty had been granted to others before me to postulate all
sorts of little circles for explaining the phenomena of the stars, I
thought I also might easily be permitted to try whether by postulating
some motion of the Earth, more reliable conclusions could be reached
regarding the revolution of the heavenly bodies, than those of my
predecessors.

And so, after postulating movements, which, farther on in the book, I
ascribe to the Earth, I have found by many and long observations that
if the movements of the other planets are assumed for the circular
motion of the Earth and are substituted for the revolution of each
star, not only do their phenomena follow logically therefrom, but
the relative positions and magnitudes both of the stars and all their
orbits, and of the heavens themselves, become so closely related that
in none of its parts can anything be changed without causing confusion
in the other parts and in the whole universe. Therefore, in the course
of the work I have followed this plan: I describe in the first book
all the positions of the orbits together with the movements which I
ascribe to the Earth, in order that this book might contain, as it
were, the general scheme of the universe. Thereafter in the remaining
books, I set forth the motions of the other stars and of all their
orbits together with the movement of the Earth, in order that one
may see from this to what extent the movements and appearances of the
other stars and their orbits can be saved, if they are transferred to
the movement of the Earth. Nor do I doubt that ingenious and learned
mathematicians will sustain me, if they are willing to recognize and
weigh, not superficiall