Leonardo da Vinci

A well-spent day brings happy sleep.

All our knowledge has its origins in our perceptions. 

Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason. 

Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. 

Art is never finished, only abandoned. 

As a well-spent day brings happy sleep, so a life well spent brings happy death. 

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

Beyond a doubt truth bears the same relation to falsehood as light to darkness. 

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

For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. 

He who is fixed to a star does not change his mind. 

He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast. 

Blinding ignorance does mislead us. O! Wretched mortals, open your eyes! 

Common Sense is that which judges the things given to it by other senses.