No human investigation can claim to be scientific if it doesn't pass the test of mathematical proof.
Inaction saps the vigor of the mind.
While you are alone you are entirely your own master and if you have one companion you are but half your own, and the less so in proportion to the indiscretion of his behavior.
Necessity is a guardian in Nature.
Not to appreciate life, all of life, is not to deserve it.
The Book of the science of Mechanics must precede the Book of useful inventions.