and perfect of their limbes, and all the rest, absolute in their numbers, as he conceiued them.  Who, as he was a happie imitator of Nature, was a most gentle expresser of it.  His mind and hand went together.  And what he thought, he vttered with that easinesse, that wee haue scarse receiued from him a blot in his papers.  But it is not our prouince, who onely gather his works, and giue them you, to praise him.  It is yours that reade him.  And there we hope, to your diuers capacities, you will finde enough, both to draw, and hold you for his wit can no more lie hid then it could be lost.  Reade him, therefore and againe and againe.  And if then you doe not like him surely you are in some manifest danger, not to vnderstand him.  And so we leaue you to other of his Friends, whom if you need can bee your guides:  if you neede them not, you can leade your selues, and others.  And such Readers we wish him.

JOHN HEMINGE HENRIE CONDELL.

[Footnote A:  Little more than half of Shakespeare’s plays were published during his lifetime; and in the publication 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  Seven years after his death, John Heminge and Henry Condell, two of his fellow-actors, collected the unpublished plays, and, in 1623, issued them along with the others in a single volume, usually known as the First Folio.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