All our knowledge has its origins in our perceptions.
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.
Science is the captain, and practice the soldiers
A beautiful body perishes, but a work of art dies not.
I have offended god and mankind because my work didn't reach the quality it should have.
Intellectual passion drives out sensuality.
Every action needs to be prompted by a motive.
You can have no dominion greater or less than that over yourself.
Art is never finished, only abandoned.
Nothing strengthens authority so much as silence.
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.
A well-spent day brings happy sleep.
The noblest pleasure is the joy of understanding.
Learning never exhausts the mind.
Water is the driving force of all nature.
The greatest deception men suffer is from their own opinions.
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.
While I thought that I was learning how to live, I have been learning how to die.
Time stays long enough for anyone who will use it.
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.
As a well-spent day brings happy sleep, so a life well spent brings happy death.
In rivers, the water that you touch is the last of what has passed and the first of that which comes; so with present time.
Many are they who have a taste and love for drawing, but no talent; and this will be discernible in boys who are not diligent and never finish their drawings with shading.
It had long since come to my attention that people of accomplishment rarely sat back and let things happen to them. They went out and happened to things.
I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do.
The natural desire of good men is knowledge.
Simplicity is the ultimate sophistication.
Tears come from the heart and not from the brain.