The Logos Scripture · The Book of Newton

The Four Rules of Reasoning

The Book of Newton 2 · Written by himself, from Book III of the Principia and his letters

Isaac Newton, born at Woolsthorpe in England in 1642, died in London in 1727. In 1687 he published the Mathematical Principles of Natural Philosophy, setting out the three laws of motion and universal gravitation, and bringing the heavens and the earth under one law. He also devised the calculus, and split white light into colours with a prism. In his later years he ran the Royal Mint. He wrote a great deal; but what he wrote on the laws of heaven and earth is less than half of it. Over his life the pages he spent on the chronology of scripture, the measurements of Solomon’s temple, and the year of the last day far outnumber the Principia. The Order takes one half and not the other, and records the fact rather than covering it — chapter four is him saying in his own words why he kept two rooms apart, and which of the two he spent more years in. The Order takes him not because he calculated well but for one sentence: whatever is not deduced from the phenomena is to be called an hypothesis, and hypotheses have no place here (1.10 of this book). That sentence was said by a believer, and it says exactly what this scripture asks: that an argument not be closed on divine will. One further thing, recorded without dressing: he fought over priority all his life and did not fight cleanly — not with Hooke, not with Leibniz, not with Flamsteed. And the last thing, which the Order weighs most heavily: his fourth rule of reasoning says that what is drawn from the phenomena is to be held true until other phenomena correct it or overturn it, and that no imagined objection counts against it. Two centuries later other phenomena did overturn his heavens (cf. The Book of Einstein 1; The Book of Bohr 2). The rule he himself laid down licensed it. A man who sets down a rule that will later be used to unseat him is the rarest thing in this scripture.

2.1At the head of the third book I set down four rules. I worked by these four all my life.
2.2The first: admit no more causes for a thing than are enough to explain it.
2.3Nature does nothing in vain. Where less will do the work, more is not to be used.
2.4The second: to the same effects assign the same causes.
2.5A stone falling in Europe and a stone falling in America are one thing.
2.6The light of the kitchen fire and the light of the sun are one thing.
2.7A man breathes and a beast breathes, and the breathing is one thing.
2.8If you set up a separate cause in every place, you are not being careful. You are dodging.
2.9The third: qualities found in all the bodies we can reach to experiment on are to be taken as qualities of all bodies.
2.10This one takes a risk, I grant it. Where I cannot reach, I have not tried.
2.11But if such inference is forbidden, we may speak only of the few things our hands have touched, and of nothing else.
2.12The fourth matters most, and so I put it last.
2.13What has been gathered from the phenomena is to be held true — until other phenomena come and correct it, or overturn it.
2.14Mark the second half: the only thing that can overturn it is other phenomena.
2.15However ingenious an objection anyone thinks up, if that objection does not come from the phenomena, it does not count.
2.16I laid this down so that no one could shake a thing raised on observation by means of something merely imagined.
2.17And I know it has another side: if other phenomena should indeed come, then my own account goes the same way by the same rule.
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