The noblest pleasure is the joy of understanding.

Any color is more distinctly seen when opposed to its contrary: thus, black on white, blear near yellow, green near red, and so on.

All our knowledge has its origins in our perceptions.

The mind that engages in subjects of too great variety becomes confused and weakened.

When you are painting you should take a flat mirror and often look at your work within it, and it will then be seen in reverse, and will appear to be by the hand of some other master, and you will be better able to judge of its faults than in any other way.

No human investigation can claim to be scientific if it doesn't pass the test of mathematical proof.

Necessity is the mistress and guide of nature.