God says to man: 'Be thou thyself, and I shall be thine.'

In humility alone lies true greatness, and knowledge and wisdom are profitable only in so far as our lives are governed by them.

A given circle cannot be so true that a truer one cannot be found; and the movement of a sphere at one moment is never precisely equal to its movement at another, nor does it ever describe two circles similar and equal, even if from appearances the opposite may seem true.

There will be a machina mundi whose centre, so to speak, is everywhere, whose circumference is nowhere, for God is its circumference and centre and He is everywhere and nowhere.

Just as all motion is from an unmovable cause, so everything divisible is from an indivisible cause. However, this visible, corporeal world is, assuredly, of a divisible nature, since what is corporeal is divisible. Therefore, this world is from an earlier, indivisible Cause.

An external thing that is knowable [is knowable] by means of something internal that is consubstantial [with the rational soul].

In every science certain things must be accepted as first principles if the subject matter is to be understood; and these first postulates rest upon faith.