If you want to know the taste of a pear, you must change the pear by eating it yourself. If you want to know the theory and methods of revolution, you must take part in revolution. All genuine knowledge originates in direct experience.

No political party can possibly lead a great revolutionary movement to victory unless it possesses revolutionary theory and knowledge of history and has a profound grasp of the practical movement.

However far man may extend himself with his knowledge, however objective he may appear to himself - ultimately he reaps nothing but his own biography.

We have no organ at all for knowledge, for truth: we know (or believe or imagine) precisely as much as may be useful in the interest of the human herd, the species: and even what is here called usefulness is in the end only a belief, something imagined and perhaps precisely that most fatal piece of stupidity by which we shall one day perish.

Be robbers and ravagers as long as you cannot be rulers and owners, you men of knowledge! The time will soon be past when you could be content to live concealed in the woods like timid deer!

Every acquisition, every step forward in knowledge is the result of courage, of severity toward oneself, of cleanliness with respect to oneself.