Many will think they can reasonably reproach me, alleging that my proofs are against the authority of certain men of great reverence in their inexperienced judgments, not considering that my matters are born under simple and pure experience, which is the true mistress.

These rules of mine are the means of making you know the true from the false, which makes men promise themselves things that are possible and with more moderation, and that you do not veil yourself in ignorance, which would cause that, obtaining no effect, you would in despair give yourself over to melancholy.

Preface.

Seeing that I cannot take a subject of great utility or note, because the men born before me have taken for themselves all the useful and necessary themes, I will do like him who, out of poverty, arrives last at the fair and, being unable to provide himself with anything else, takes all the things already seen by others and not accepted but rejected for their little worth. This despised and refused merchandise, left over from the many buyers, I will place upon my weak burden, and with it I will go distributing, not through the great cities but through poor villages, taking such reward as the thing given by me deserves.

On the muscles.

Nature has ordained in man the muscles as officials, pullers of the nerves, which can move the limbs according to the will and desire of the common sense, in the likeness of the officials distributed by a lord through various provinces and cities, who in those places represent and obey the will of that lord. And that official who in a single case has most obeyed the commands given him by mouth from his lord will afterwards do of himself, in the same case, a thing that will not depart from the will of that lord. So one often sees the fingers do, which, learning with utmost obedience the things upon an instrument that are commanded them by the judgment, after that learning will play them without the judgment attending to it. Do not the muscles that move the legs still perform their office without the man knowing it?

On the growth of man.

Man in 3 years will have formed half of his height.

The female of equal size to the man weighs less than him.

The dead female lies face down upon the waters, and the man lies face up.

On the limbs.

If nature had fixed a single rule in the qualities of the members, all the faces of men would be so alike that one could not be told from another. But she has so varied the five members of the face that, although she has made an almost universal rule as to their size, she has not observed them in their qualities in such a way that one can clearly be told from another.

On the eye.

Because the eye is the window of the soul, she is always in fear of losing it, in such a way that, a thing being moved before it that suddenly frightens the man, he does not with his hands succor the heart, source of life, nor the head, receptacle of the lord of the senses, nor hearing, nor smell or taste; rather at once the frightened sense, not content to close the eyes with their lids shut with utmost force, at once turns it to the opposite side; and, not feeling safe, he still places one hand there and extends the other, making a vanguard against his fear.

Again nature has ordained that the eyes in the head of man, by themselves with the lid, [close] … so that, not being watched over by the sleeping man, it may not be injured by anything.

All animals of great fear sleep with their eyes open, like the …

Preface on perspective, that is, on the office of the eye.

Now consider, reader, what we can believe of our ancients, who wished to define what soul and life are — things unprovable — when those things that by experience can at every moment be clearly known and proven have for so many centuries been ignored and falsely believed. The eye, which so clearly gives experience of its office, has up to my times been defined in one way by countless authors; I find by experience it to be another.

Preface.

Naturally, good men desire to know.

I know that many will say this to be a useless work, and these will be those of whom Demetrius said he took no more account of the wind that caused words in their mouth than of the wind that issued from their lower parts. Men who have only the desire for riches and bodily pleasure, and are wholly deprived of that of wisdom, the food and truly secure riches of the soul; for as much as the soul is more worthy than the body, so much more worthy are the riches of the soul than of the body. And often, when I see one of these take this work in hand, I doubt whether, like the monkey, they will put it to their nose, or ask me if it is something to eat.

Preface.

I well know that, because I am not lettered, some presumptuous person will think he can reasonably blame me by alleging that I am a man without letters. Foolish people! Do they not know that I could, as Marius answered against the Roman patricians, answer likewise by saying: those who adorn themselves with the labors of others will not concede to me my own. They will say that, because I have no letters, I cannot well say what I wish to treat of. Do they not know that my matters are more to be drawn from experience than from the words of others, which was the mistress of those who wrote well, and so I take her as my mistress and will in all cases cite her?