Necessity is the mistress and guide of nature. Necessity is the theme and the inventress, the eternal curb and law of nature.
Nature never breaks her own laws.
Nature is the source of all true knowledge. She has her own logic, her own laws, she has no effect without cause nor invention without necessity.
Nature is full of infinite causes that have never occurred in experience.
Movement will cease before we are weary of being useful.
Men of lofty genius when they are doing the least work are most active.
Medicine is the restoration of discordant elements; sickness is the discord of the elements infused into the living body.
Mechanics are the Paradise of mathematical sciences, because here we come to the fruits of mathematics.
Let no man who is not a Mathematician read the elements of my work.
Learning never exhausts the mind.
Learning acquired in youth arrests the evil of old age.
Just as food eaten without appetite is a tedious nourishment, so does study without zeal damage the memory by not assimilating what it absorbs.