The nature of matter, or body considered in general, consists not in its being something which is hard or heavy or coloured, or which affects the senses in any way, but simply in its being something which is extended in length, breadth and depth.

Everybody thinks himself so well supplied with common sense that even those most difficult to please. . . never desire more of it than they already have.

He lives well who is well hidden.

I am indeed amazed when I consider how weak my mind is and how prone to error.

But I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming.

Omnia apud me mathematica fiunt.

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