Those who condemn the supreme certainty of mathematics feed on confusion, and can never silence the contradictions of the sophistical sciences which lead to eternal quackery.

Affective gestures pointing to things near either in time or space should be made with the hand not very far from the body of the person pointing; and if these things are distant, the hand of the painter should be more extended and the face turned toward the person to whom he is addressing the demonstration.

O Lord, thou givest us everything, at the price of an effort.

The merit of painting lies in the exactness of reproduction. Painting is a science and all sciences are based on mathematics. No human inquiry can be a science unless it pursues its path through mathematical exposition and demonstration.

Being willing is not enough. We must do.

The painter strives and competes with nature.

We are deceived by promises and time disappoints us.