We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.

Every action needs to be prompted by a motive.

Make your faces so that they do not all have the same expression, as one sees with most painters, but give them different expression, according to age, complexion, and good or bad character.

Perspective is a most subtle discovery in mathematical studies, for by means of lines it causes to appear distant that which is near, and large that which is small.

The earth is moved from its position by the weight of a tiny bird resting upon it.

Sculptured figures which appear in motion, will, in their standing position, actually look as if they were falling forward.

He who wishes to see how the soul inhabits the body should look to see how that body uses its daily surroundings. If the dwelling is dirty and neglected, the body will be kept by its soul in the same condition, dirty and neglected.