The fox when it sees a flock of herons or magpies or birds of that kind, suddenly flings himself on the ground with his mouth open to look as he were dead; and these birds want to peck at his tongue, and he bites off their heads.

The memory of benefits is a frail defence against ingratitude.

But to me all sciences seem vain and full of error that are not born of experience, mother of all certainty, and do not terminate in an actual experience.

I wish to work miracles.

It is better to imitate ancient than modern work.

It is an acknowledged fact that we perceive errors in the work of others more readily than in our own.

I say that the power of vision extends through the visual rays to the surface of non-transparent bodies, while the power possessed by these bodies extends to the power of vision.