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

Now therefore, that my mind is free from all cares, and that I have obtained for myself assured leisure in peaceful solitude, I shall apply myself seriously and freely to the general destruction of all my former opinions.

With me, everything turns into mathematics.

Omnia apud me mathematica fiunt.

Whatever I have up till now accepted as most true and assured I have gotten either from the senses or through the senses. But from time to time I have found that the senses deceive, and it is prudent never to trust completely those who have deceived us even once.

Divide each difficulty at hand into as many pieces as possible and as could be required to better solve them.

Except our own thoughts, there is nothing absolutely in our power.