Isaac Newton on Mathematics 1687
Channel: Age of Enlightenment
Date: 2015-11-03

Isaac Newton wrote  Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"). It was first published in 1687.  These are his four rules of reasoning in philosophy from the text.

Rule 1: We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.

Rule 2: Therefore to the same natural effects we must, as far as possible, assign the same causes.

Rule 3: The qualities of bodies, which admit neither intensification nor remission of degrees, and which are found to belong to all bodies within the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.

Rule 4: In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, not withstanding any contrary hypothesis that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.

Here is the text from the whole book.
http://www.gutenberg.org/ebooks/28233