The acquisition of knowledge is always of use to the intellect, because it may thus drive out useless things and retain the good. For nothing can be loved or hated unless it is first known.
Leonardo da VinciAnyone who invokes authors in discussion is not using his intelligence but his memory.
Leonardo da VinciThere is no result in nature without a cause; understand the cause and you will have no need of the experiment.
Leonardo da VinciDemetrius was wont to say that there was no difference between the words and speech of the unskilled and ignorant and the sounds and rumblings caused by the stomach being full of superfluous wind. This he said, not without reason, for, as he held, it did not in the least matter from what part of them the voice emanated, whether from the lower parts or the mouth, since the one and the other were of equal worth and importance.
Leonardo da Vinci