No human investigation can be called real science if it cannot be demonstrated mathematically.
Just as courage imperils life, fear protects it.
Nature is full of infinite causes that have never occurred in experience.
Men born in hot countries love the night because it refreshes them and have a horror of light because it burns them.
It is the infinite alone that cannot be attained, for if it could it would become finite.
Motion is created by the destruction of balance.
Men of lofty genius when they are doing the least work are most active.
The eye transmits its own image through the air to all the objects which face it, and also receives them on its own surface, whence the “sensus communis” takes them and considers them.
The human foot is a masterpiece of engineering and a work of art.
Why does the eye see a thing more clearly in dreams than the imagination when awake?
The color of the object illuminated partakes of the color of that which illuminates it.
Love shows itself more in adversitythan in prosperity; as light does, which shines most where the place isdarkest.
For those colours which you wish to be beautiful, always first prepare a pure white ground.
Wisdom is the daughter of experience.
Life well spent is long.
Men wrongly lament the flight of time, blaming it for being too swift; they do not perceive that its passage is sufficiently long, but a good memory, which nature has given to us, causes things long past to seem present.
I roamed the countryside searching for answers to things I did not understand.
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.
The human bird shall take his first flight, filling the world with amazement, all writings with his fame, and bringing eternal glory to the nest whence he sprang.
Reprove your friend in secret and praise him openly.