All our knowledge originates in opinion.
For youth, everything is sport.
Learning acquired in youth arrests the evil of old age; and if you understand that old age has wisdom for its food, you will so conduct yourself in youth that your old age will not lack for nourishment.
Things that are separate shall be united and acquire such virtue that they will restore to man his lost memory.
A day will come in which men will look upon an animal's murder the same way they look today upon a man's murder.
The fame of the rich man dies with him; the fame of the treasure, and not of the man who possessed it, remains.
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.
When you draw a nude, sketch the whole figure and nicely fit the members to it and to each other. Even though you may only finish one portion of the drawing, just make certain that all the parts hang together, so that the study will be useful to you in the future.
Men born in hot countries love the night because it refreshes them and have a horror of light because it burns them.
Instrumental or mechanical science is the noblest and above all others, the most useful.
In whatever system where the weight attached to the wheel should be the cause of motion of the wheel, without any doubt the center of the gravity of the weight will stop beneath the center of its axle. No instrument devised by human ingenuity, which turns with its wheel, can remedy this effect. Oh, speculators about perpetual motion, how many vain chimeras have you created in the like quest. Go and take you place with the seekers after gold.
Man and animals are in reality vehicles and conduits of food, tombs of animals, hostels of Death, coverings that consume, deriving life by the death of others.
The acquisition of knowledge is always of use to the intellect, because it may thus drive out useless things and retain the good. For nothing can be loved or hated unless it is first known.
Black is like a broken vessel, which is deprived of the capacity to contain anything.
O Time with your teethy years! You swallow up all things little by little in a slow-motion, wrinkling process of dying.
Experiment is the sole interpreter of the artifices of Nature.
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.
When the thing taken into union is perfectly adapted to that which receives it, the result is delight and pleasure and satisfaction.
The art of procreation and the members employed therein are so repulsive, that if it were not for the beauty of the faces and the adornments of the actors and the pent-up impulse, nature would lose the human species.
Painting is concerned with the ten things you can see: these are darkness and brightness, substance and color, form and place, remoteness and nearness, movement and rest.
Who sows virtue reaps honor.
The eye, the window of the soul, is the chief means whereby the understanding can most fully and abundantly appreciate the infinite works of Nature; and the ear is second.
Test knowledge through experience, be prepared to make mistakes, and be persistent about it.
It is an acknowledged fact that we perceive errors in the work of others more readily than in our own.
One day the world will look upon research upon animals as it now looks upon research on human beings.
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