Doubt is the origin of wisdom

If I found any new truths in the sciences, I can say that they follow from, or depend on, five or six principal problems which I succeeded in solving and which I regard as so many battles where the fortunes of war were on my side.

The entire method consists in the order and arrangement of the things to which the mind's eye must turn so that we can discover some truth.

Thus each truth discovered was a rule available in the discovery of subsequent ones.

The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge.

When writing about transcendental issues, be transcendentally clear.

De omnibus dubitandum