Nothing comes out of nothing.

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.

Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.

The only thing that I know, is that I know nothing

The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.

But possibly I am something more than I suppose myself to be.

Here I beg you to observe in passing that the scruples that prevented ancient writers from using arithmetical terms in geometry, and which can only be a consequence of their inability to perceive clearly the relation between these two subjects, introduced much obscurity and confusion into their explanations.