Leonardo da Vinci

"Experience never errs; it is only your judgments that err by promising themselves effects such as are not caused by your experiments."

"Experience does not err; only your judgments err by expecting from her what is not in her power. Men wrongly complain of Experience; with great abuse they accuse her of leading them astray but they set Experience aside, turning from it with complaints as to our ignorance causing us to be carried away by vain and foolish desires to promise ourselves, in her name, things that are not in her power; saying that she is fallacious. Men are unjust in complaining of innocent Experience, constantly accusing her of error and of false evidence."

"Every instrument requires to be made by experience."

"The man who blames the supreme certainty of mathematics feeds on confusion, and can never silence the contradictions of sophistical sciences which lead to an eternal quackery."

"There is no certainty in sciences where one of the mathematical sciences cannot be applied, or which are not in relation with these mathematics."

"Any one who in discussion relies upon authority uses, not his understanding, but rather his memory. Good culture is born of a good disposition; and since the cause is more to be praised than the effect, I will rather praise a good disposition without culture, than good culture without the disposition."

"Science is the captain, and practice the soldiers."

"Those who fall in love with practice without science are like a sailor who enters a ship without a helm or a compass, and who never can be certain whither he is going."

"Now you see that the hope and the desire of returning home and to one's former state is like the moth to the light, and that the man who with constant longing awaits with joy each new spring time, each new summer, each new month and new year — deeming that the things he longs for are ever too late in coming — does not perceive that he is longing for his own destruction. But this desire is the very quintessence, the spirit of the elements, which finding itself imprisoned with the soul is ever longing to return from the human body to its giver. And you must know that this same longing is that quintessence, inseparable from nature, and that man is the image of the world."

"O Time! consumer of all things; O envious age! thou dost destroy all things and devour all things with the relentless teeth of years, little by little in a slow death. Helen, when she looked in her mirror, seeing the withered wrinkles made in her face by old age, wept and wondered why she had twice been carried away."

"The knowledge of past times and of the places on the earth is both an ornament and nutriment to the human mind."

"To lie is so vile, that even if it were in speaking well of godly things it would take off something from God's grace; and Truth is so excellent, that if it praises but small things they become noble."

"Beyond a doubt truth bears the same relation to falsehood as light to darkness; and this truth is in itself so excellent that, even when it dwells on humble and lowly matters, it is still infinitely above uncertainty and lies, disguised in high and lofty discourses; because in our minds, even if lying should be their fifth element, this does not prevent that the truth of things is the chief nutriment of superior intellects, though not of wandering wits. But you who live in dreams are better pleased by the sophistical reasons and frauds of wits in great and uncertain things, than by those reasons which are certain and natural and not so far above us."

"Avoid studies of which the result dies with the worker."

"Men are in error when they lament the flight of time, accusing it of being too swift, and not perceiving that it is sufficient as it passes; but good memory, with which nature has endowed us, causes things long past to seem present."

"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."

"The acquisition of any 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."

"As a day well spent procures a happy sleep, so a life well employed procures a happy death."

"The water you touch in a river is the last of that which has passed, and the first of that which is coming. Thus it is with time present."

"Just as eating against one’s will is injurious to health, so studying without a liking for it spoils the memory, and it retains nothing it takes in."

"Just as iron rusts unless it is used, and water putrifies or, in cold, turns to ice, so our intellect spoils unless it is kept in use."

"You do ill if you praise, and still worse if you reprove in a matter you do not understand."

"It seems to me that men of coarse and clumsy habits and of small knowledge do not deserve such fine instruments nor so great a variety of natural mechanism as men of speculation and of great knowledge; but merely a sack in which their food may be stowed and whence it may issue, since they cannot be judged to be any thing else than vehicles for food; for it seems to me they have nothing about them of the human species but the voice and the figure, and for all the rest are much below beasts."

"Some there are who are nothing else than a passage for food and augmentors of excrement and fillers of privies, because through them no other things in the world, nor any good effects are produced, since nothing but full privies results from them."

"The greatest deception men suffer is from their own opinions."

"Blind ignorance misleads us thus and delights with the results of lascivious joys. Because it does not know the true light. Because it does not know what is the true light. Vain splendour takes from us the power of being .... behold! for its vain splendour we go into the fire, thus blind ignorance does mislead us. That is, blind ignorance so misleads us that... O! wretched mortals, open your eyes."

"That is not riches, which may be lost; virtue is our true good and the true reward of its possessor. That cannot be lost; that never deserts us, but when life leaves us. As to property and external riches, hold them with trembling; they often leave their possessor in contempt, and mocked at for having lost them."

"Man has much power of discourse which for the most part is vain and false; animals have but little, but it is useful and true, and a small truth is better than a great lie."

"He who possesses most must be most afraid of loss."

"He who wishes to be rich in a day will be hanged in a year."

"That man is of supreme folly who always wants for fear of wanting; and his life flies away while he is still hoping to enjoy the good things which he has with extreme labour acquired."

"We ought not to desire the impossible."

"Ask counsel of him who rules himself well."

"Chi non punisce il male comanda che si faccia."

"The grave will fall in upon him who digs it."

"You can have no dominion greater or less than that over yourself."

"Chi poco pensa, molto erra."

"It is easier to contend with evil at the first than at the last."

"Where there is most feeling, there is the greatest martyrdom."

"The memory of benefits is a frail defence against ingratitude."

"Reprove your friend in secret and praise him openly."

"Be not false about the past."

"O sleepers! what a thing is slumber! Sleep resembles death. Ah, why then dost thou not work in such wise as that after death thou mayst retain a resemblance to perfect life, when, during life, thou art in sleep so like to the hapless dead?"

"Painting is poetry which is seen and not heard, and poetry is a painting which is heard but not seen. These two arts, you may call them both either poetry or painting, have here interchanged the senses by which they penetrate to the intellect."

"Oysters open completely when the moon is full; and when the crab sees one it throws a piece of stone or seaweed into it and the oyster cannot close again so that it serves the crab for meat. Such is the fate of him who opens his mouth too much and thereby puts himself at the mercy of the listener."

"The painter strives and competes with nature...There is nothing in all nature without its reason. If you know the reason, you do not need the experience..."

"Look at the grace and sweetness of men and women in the street..."

"Thou, O God, sellest us all benefits, at the cost of our toil...."

"As a day well spent makes sleep seem pleasant, so a life well employed makes death pleasant. A life well spent is long."

"It is the infinite alone that cannot be attained, for if it could it would become finite."