A man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding.
The synthesis consists in assuming the Causes discovered and established as Principles, and by them explaining the Phænomena proceeding from them, and proving the explanations.
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.
