Whoever does not respect life, does not deserve it.

Those who are in love with practice without knowledge are like the sailor who gets into a ship without rudder or compass and who never can be certain whether he is going. Practice must always be founded on sound theory, and to this Perspective is the guide and the gateway; and without this nothing can be done well in the matter of drawing.

A day will come in which men will look upon an animal's murder the same way they look today upon a man's murder.

A good memory, which nature has endowed us with, causes things long past to seem present.

If you find from your own experience that something is a fact and it contradicts what some authority has written down, then you must abandon the authority and base your reasoning on your own findings.

Necessity is a guardian in Nature.

People of higher talent work, even if they seem to do nothing