Leonardo da Vinci

He who does not punish evil commands it to be done.

The value of a thing is in its use.

No human investigation can be called true science if it doesn't pass through mathematical demonstrations.

The water that you touch in a river is the last of that which has passed, and the first of that which comes; so with present time.

Oh, how many times have I been deceived by my own opinions!

I have offended God and mankind because my work didn't reach the quality it should have.

I love those who can smile in trouble.

Where the spirit does not work with the hand, there is no art.

An average human looks without seeing, listens without hearing, touches without feeling, eats without tasting, moves without physical awareness, inhales without awareness of odour or fragrance, and talks without thinking.

Experience does not err. Only your judgments err by expecting from her what is not in her power.

As every divided kingdom falls, so every mind divided between many studies confounds and saps itself.

Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature, because in her inventions nothing is lacking and nothing is superfluous.

It is better to imitate ancient than modern work.

Poor is the pupil who does not surpass his master.

Men will seem like wooden puppets, moving without reason.

The act of procreation and anything that has any relation to it is so disgusting that human beings would soon die out if it were not a traditional custom and if there were no pretty faces and sensuous dispositions.

I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do.

Learning never exhausts the mind.

Art is never finished, only abandoned.

Water is the driving force of all nature.