"You will perhaps say that the sinews and muscles of a bird are incomparably more powerful than those of a man... But the reply to this is that such great strength gives it a reserve of power beyond what it ordinarily uses..."

"If you take as your pattern the wings of feathered birds, these are more powerful in structure of bone and sinew because they are penetrable, that is to say the feathers are separated from one another and the air passes through them. But the bat is aided by its membrane, which binds the whole together and is not penetrated by the air."

"Remember that your bird should have no other model than the bat, because its membranes serve as an armour or rather as a means of building together the pieces of its armour, that is the framework of the wings."

"Every body that is moved continues to move so long as the impression of the force of its mover is retained in it, therefore the movement of this wing with violence... will come to move the whole bird with it until the impetus of the moved air has been consumed."

"A bird makes the same use of wings and tail in the air as a swimmer does of his arms and legs in the water."

"Since the wings are swifter to press the air than the air is to escape from beneath the wings the air becomes condensed and resists the movement of the wings; and the motive power of these wings by subduing the resistance of the air raises itself in a contrary movement to the movement of the wings."

"He who suffers time to slip away and does not grow in virtue the more one thinks about him the sadder one becomes. No man has a capacity for virtue who sacrifices honour for gain. Fortune is powerless to help one who does not exert himself. That man becomes happy who follows Christ. There is no perfect gift without great suffering. Our triumphs and our pomps pass away; gluttony and sloth and enervating luxury have banished every virtue from the world; so that as it were wandering from its course our nature is subdued by habit. Now and henceforth it is meet that you cure yourself of laziness. The Master has said that sitting on down or lying under the quilts will not bring thee to fame. He who without it has frittered life away leaves no more trace of himself upon the earth than smoke does in the air or the foam on the water."

"Wine is good, but water is preferable at table."

"Nature is full of infinite causes which were never set forth in experience."

"He who does not value life does not deserve it."

"The water which rises in the mountain is the blood which keeps the mountain in life."

"Observe the light and consider its beauty. Blink your eye and look at it. That which you see was not there at first, and that which was there is there no more."

"To enjoy—to love a thing for its own sake and for no other reason."

"Science, knowledge of the things that are possible present and past; prescience, knowledge of the things which may come to pass."

"Where there is most power of feeling, there of martyrs is the greatest martyr."

"Intellectual passion drives out sensuality."

"While I thought I have been learning how to live, I have been learning how to die."

"The mind passes in an instant from east to west; and all the great incorporeal things resemble these very closely in speed."

"Every part is disposed to unite with the whole, that it may thereby escape from its own incompleteness."

"Reserve the great matters till the end, and the small matters give at the beginning."

"If any man could have discovered the utmost powers of the cannon, in all its various forms and have given such a secret to the Romans, with what rapidity would they have conquered every country and have vanquished every army, and what reward could have been great enough for such a service! Archimedes indeed, although he had greatly damaged the Romans in the siege of Syracuse, nevertheless did not fail of being offered great rewards from these very Romans; and when Syracuse was taken, diligent search was made for Archimedes; and he being found dead greater lamentation was made for him by the Senate and people of Rome than if they had lost all their army; and they did not fail to honour him with burial and with a statue."

"I ask at what part of its curved motion the moving cause will leave the thing moved and moveable."

"Do not reveal, if liberty is precious to you; my face is the prison of love."

"Tell me if anything was ever done."

"When I did well, as a boy you used to put me in prison. Now if I do it being grown up, you will do worse to me."

"This writing distinctly about the kite seems to be my destiny, because among the first recollections of my infancy, it seemed to me that, as I was in my cradle, a kite came to me and opened my mouth with its tail, and struck me several times with its tail inside my lips."

"The eye can best distinguish the forms of objects when it is placed between the shaded and the illuminated parts."

"Be not false about the past."

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

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

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

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

"Chi poco pensa, molto erra."

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

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

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

"Ask counsel of him who rules himself well."

"We ought not to desire the impossible."

"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."

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

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

"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."

"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."

"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."

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

"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."

"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."

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

"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."

"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."