All our knowledge originates in opinion.

He who cannot establish dominion over himself will have no dominion over others.

Blinding ignorance does mislead us. O! Wretched mortals, open your eyes!

Of the four elements water is the second in weight and the second in respect of mobility. It is never at rest until it unites with the sea.

When you put your hand in a flowing stream, you touch the last that has gone before and the first of what is still to come.

Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer.

I am not to blame for putting forward, in the course of my work on science, any general rule derived from a previous conclusion.