You just keep pushing. You just keep pushing. I made every mistake that could be made. But I just kept pushing.

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

I can doubt everything, except one thing, and that is the very fact that I doubt. Simply put - I think, therefore I am

The only secure knowledge is that I exist.

Neither the true nor the false roots are always real; sometimes they are imaginary; that is, while we can always imagine as many roots for each equation as I have assigned, yet there is not always a definite quantity corresponding to each root we have imagined.

For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it.

Everything is self-evident.