Newton’s Principia

In reading prefaces to various works collected in the Harvard Classics (limited edition set no. 1312, purchased by my grandfather but never read, so that I had to slit open the folded pages with a knife), I was struck by the clarity and scope of the preface to Newton’s Principia. Newton announces an explanation of “the system of the World” by deducing the planetary orbits and the terrestrial tides by calculus from his new law of gravity. Then he says he wishes he could similarly derive “the rest of the phenomena of nature” from as yet undiscovered laws of attraction and repulsion between small particles. In the last sentence quoted below he explains how he deals with what was an annoying problem for writers before TeX.

From Preface to the Philosophiae Naturalis Principia Mathematica

by Sir Isaac Newton (1642-1727)

…In the third book we give…the explication of the system of the World; for by the propositions mathematically demonstrated in the first book, we there derive from the celestial phenomena the forces of gravity with which bodies tend to the sun and the several planets. Then , from these forces, by other propositions which are also mathematical, we deduce the motions of the planets, the comets, the moon, and the sea. I wish we could derive the rest of the phenomena of nature by the same kind of reasoning from mechanical principles; for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, but some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown, philosophers have hitherto attempted the search of nature in vain;…

…Some things, found out after the rest, I chose to insert in places less suitable, rather than change the number of the propositions and the citations. …

Cambridge, Trinity College, May 8, 1686                      Isaac Newton

Incidentally, also interesting are Samuel Johnson’s Preface to the English Dictionary (1755), mainly a defense against expected criticism, and his preface to Shakespeare (1765), praise for his accurate depiction of humanity followed by a litany of criticisms.

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