It is reasonable that forces directed toward bodies depend on the nature and the quantity of matter of such bodies, as happens in the case of magnetic bodies.
Every particle of matter is attracted by or gravitates to every other particle of matter with a force inversely proportional to the squares of their distances.
Hypotheses should be subservient only in explaining the properties of things but not assumed in determining them, unless so far as they may furnish experiments.
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.
