I Do Not Feign Hypotheses.

It Is Indeed A Matter Of Great Difficulty To Discover, And Effectually To Distinguish, The True Motions Of Particular Bodies From The Apparent; Because The Parts Of That Immovable Space, In Which Those Motions Are Performed, Do By No Means Come Under The Observation Of Our Senses. Yet The Thing Is Not Altogether Desperate; For We Have Some Arguments To Guide Us, Partly From The Apparent Motions, Which Are The Differences Of The True Motions; Partly From The Forces, Which Are The Causes And Effects Of The True Motions.

To Derive Two Or Three General Principles Of Motion From Phænomena, And Afterwards To Tell Us How The Properties And Actions Of All Corporeal Things Follow From Those Manifest Principles, Would Be A Very Great Step In Philosophy.

I Am Ashamed To Tell You To How Many Figures I Carried These Calculations [of Pi], Having No Other Business At The Time

Physics, Beware Of Metaphysics.

I Have Presented Principles Of Philosophy That Are Not, However, Philosophical But Strictly Mathematical-that Is, Those On Which The Study Of Philosophy Can Be Based. These Principles Are The Laws And Conditions Of Motions And Of Forces, Which Especially Relate To Philosophy.