Download Excerpts from Mathematical Principles of Natural Philosophy

Excerpts from Mathematical Principles of Natural Philosophy (“General Scholium”)and
Philosophical Transactions of the Royal Society (letter on colors)
by Isaac Newton
Isaac Newton (1642-1727), arguably the most important figure in all of science, believed
that scientific knowledge is proven, in a manner analogous to proofs in geometry. Like
the leading scientists of his day, such as Galileo and Descartes, he thought that “more
geometrico” (the geometrical method) was the method of science. His famous scientific
work on motion and gravity (Mathematical Principles of Natural Philosophy) was written
in the manner of a geometry text, as a series of theorems deduced from axioms. This is
very different from the way scientific works are presented today. One reason for his odd
method is his rejection of the method of hypotheses, where the scientist suggests
various ways of explaining the phenomena being studied, and then tests, rejects, and
refines these suggestions, until an adequate explanation is found. This won’t do, argues
Newton (in his letter on colours of 1672), since we can never be sure we have counted
and considered all of the possible hypotheses. What we must do instead is prove our
theory by means of experiment. We might ask how we know that what holds true in any
given experiment will also hold true everywhere else. Perhaps Newton’s faith in
experimental proof was underwritten by his belief that God played a role in physics as
the maker and maintainer of the world. Since God “constitutes duration and space,” the
core concepts of physics, time and space, must therefore be ideally regulated by God,
thus physical experimentation could only reveal this ideal order.
Study Questions:
Are there always more than one possible hypothesis which could explain any
phenomenon? Are there indefinitely many?
Why does Newton think a “perfect enumeration” of hypotheses is impossible?
He speaks of deducing properties from experiments -- what does he mean by
this?
Does God play a part in Newton’s physics (his three laws of motion, model of the
solar system, etc.), or in his scientific method, or both?
Why can we never know the real substance of anything? What implications does
this have for scientific method?
Why is Newton not worried by the fact that he cannot discover the cause of
gravity?
What does Newton mean by “rendered general by induction”? Is this the same
thing as deduction from experiment?