lication of these there
is no evidence that the author had any hand. Seven years after his
death, John Heminge and Henry Condell, two of his fellow-actors,
collected the unpublished plays, and, in 1623, issued them along with
the others in a single volume, usually known as the First Folio.
When one considers what would have been lost had it not been for the
enterprise of these men, it seems safe to say that the volume they
introduced by this quaint and not too accurate preface, is the most
important single book in the imaginative literature of the world.]

PREFACE TO THE PHILOSOPHIAE NATURALIS PRINCIPIA MATHEMATICA

BY SIR ISAAC NEWTON. (1686)[A]

Since the ancients (as we are told by Pappus) made great account of
the science of mechanics in the investigation of natural things; and
the moderns, laying aside substantial forms and occult qualities,
have endeavored to subject the phenomena of nature to the laws of
mathematics, I have in this treatise cultivated mathematics so far as
it regards philosophy. The ancients considered mechanics in a twofold
respect; as rational, which proceeds accurately by demonstration, and
practical. To practical mechanics all the manual arts belong, from
which mechanics took its name. But as artificers do not work with
perfect accuracy, it comes to pass that mechanics is so distinguished
from geometry, that what is perfectly accurate is called geometrical;
what is less so is called mechanical. But the errors are not in the
art, but in the artificers. He that works with less accuracy is an
imperfect mechanic: and if any could work with perfect accuracy, he
would be the most perfect mechanic of all; for the description of
right lines and circles, upon which geometry is founded, belongs
to mechanics. Geometry does not teach us to draw these lines, but
requires them to be drawn; for it requires that the learner should
first be taught to describe these accurately, before he enters upon
geometry; then it shows how by these operations problems may be
solved. To describe right lines and circles are problems, but not
geometrical problems. The solution of these problems is required from
mechanics; and by geometry the use of them, when so solved, is shown;
and it is the glory of geometry that from those few principles,
fetched from without, it is able to produce so many things. Therefore
geometry is founded in mechanical practice, and is nothing but that
part of universal mechanics which acc