I am an investigator by inclination. I feel a great thirst for knowledge.

Nature does nothing in vain, and in the use of means to her goals she is not prodigal.

All false art, all vain wisdom, lasts its time but finally destroys itself, and its highest culture is also the epoch of its decay.

The death of dogma is the birth of morality.

Freedom is independence of the compulsory will of another, and in so far as it tends to exist with the freedom of all according to a universal law, it is the one sole original inborn right belonging to every man in virtue of his humanity.

All our knowledge begins with the senses...

Every human being should always be treated as an end and never as a mere instrument.