The painter who has no doubt about his own ability will attain very little.

Weight is caused by one element being situated in another; and it moves by the shortest line towards its centre, not by its own choice, not because the centre draws it to itself, but because the other intervening element cannot withstand it.

The organ of perception acts more readily than judgment.

To be a winner you must want to win but must know of the chance of losing and must not fear of it.

In whatever system where the weight attached to the wheel should be the cause of motion of the wheel, without any doubt the center of the gravity of the weight will stop beneath the center of its axle. No instrument devised by human ingenuity, which turns with its wheel, can remedy this effect. Oh, speculators about perpetual motion, how many vain chimeras have you created in the like quest. Go and take you place with the seekers after gold.

Why does the eye see a thing more clearly in dreams than the imagination when awake?

The faculty of imagination is both the rudder and the bridle of the senses.