Translated by Michael S. Mahoney

[To William of Paris]

Chapter I: About and against feigned appearances, and about and against invocations of spirits

I shall respond carefully to your inquiry. Now, although nature is powerful and marvelous, yet art using nature as an instrument is more powerful than natural strength, as we see in many things. But whatever lies beyond the workings of nature or of art either is not human or is feigned and filled with deception. For there are those who feign appearances by the quick motion of their hands, or by changing their voice, or by the subtlety of their instruments, or by use of darkness or of consensus; and they set before mortals many things to be marveled at, which do not in fact exist. The world is full of such people, as is clear to anyone who looks around. Jugglers counterfeit many things by the speed of their hands, and ventriloquists, by putting together a variety of sounds in the belly, the throat, and the mouth, form at will human voices either far away or close by, as if a spirit were speaking to a man; they can even feign the sound of animals. But reed pipes hidden in the grass and buried in the recesses of the earth show us that it is the human voice, not that of spirits, that is feigned by great deceit. And when, in the shadows of morning or evening twilight, inanimate objects move rapidly, it is not truth, but fraud and deceit. Also, consensus fabricates everything men want, insofar as they agree with one another.

None of these things is the subject of philosophical inquiry, nor does it accord with art or the power of nature. Rather, for this reason, it is a vile business when, contrary to the laws of philosophy and to all reason, men invoke nefarious spirits in order to bend them to their will. They even err in believing that they subject the spirits to themselves in order to compel them by human power. For this is impossible: human power is inferior by far to that of the spirits. But men of this sort err even more in believing that they summon or drive away the spirits by some natural objects they use. And men have hitherto erred when, by invocations, deprecations, and sacrifices, they have endeavored to placate the spirits and employ them for the benefit of the invocators, for it is incomparably easier to entreat God or the good spirits for whatever man deems useful. Favorable malign spirits do not exist in noxious things, except insofar as, due to the sins of man, they are permitted by God, who rules and governs the human race. And therefore these paths are beyond the teachings of wisdom, nay, rather they operate contrary to them, and true philosophers have attended to none of these six modes.

Chapter II: On symbols and incantations and their use

My thoughts on incantations and symbols and other things of that sort are as follows. Without a doubt all such things at the present time are false and doubtful. Those that philosophers introduce into the works of nature and art in order to hide secrets from the unworthy are totally irrational. For example, if it were wholly unknown that a magnet attracts iron and someone wanting to carry out this operation before the public were to make signs and offer incantations, lest it be seen that the whole business of attraction is natural, the whole affair would be an error. In this way, therefore, many things are hidden in many ways in the words of the philosophers, and the wise man should have the prudence to neglect the incantations and signs and to examine the work of nature and of art. In that way, he will see that both animate and inanimate things rush together in conformity with nature and not due to the power of signs and incantations. So many secrets of nature and of art are thought magical by the unlearned, and the magicians trust foolishly in symbols and incantations to bring them power; pursuing them, they leave behind the work of nature and of art for the sake of the error of incantations and symbols. And thus, urged on by their own folly, both sorts of these men are deprived of useful knowledge.

But there are some deprecations instituted in ancient times by men of truth, or rather ordained by God and the angels, and prayers of this sort can retain their original power. In many areas, for example, certain oaths are still made over glowing iron and on the water of rivers, and similarly there are other ordeals by which the innocent are vindicated and criminals condemned; these take place by the authority of the Church and its prelates. Indeed, priests themselves exorcise with holy water, just as one reads in the ancient law of the water of purgation by which one tests whether a woman is an adulteress or is faithful to her husband. There are many things of this sort. But by law one should avoid all those things contained in the books of the magicians, even though they may contain some truth. For they employ so many false things that one cannot distinguish between true and false. Whence one must reject whatever the magicians say about this or that book which Solomon or other wise men wrote, because books of this sort are accepted not by the authority of the Church or by vise men, but by seducers who would deceive the world. For the latter even write new books and multiply new fabrications (as we know by experience) and then, in order to entice men more forcefully, they prefix to their own works famous titles and boldly ascribe them to great authors. Also, in order to omit no outward appearances, they adopt a lofty style and fabricate their lies in the form of texts.

Symbols are either words composed of letters and contain the meaning of contrived speech, or they represent configurations of the stars at auspicious times. Hence. one should judge the former symbols in accordance with what has been said concerning incantations. Concerning the latter symbols, it is known that, if they are not made at the proper time, they have no efficacy whatever. For that reason, every wise man is of the opinion that anyone who forms the symbols as they are drawn in books, referring only to the figure they are copying as exemplar, accomplishes nothing. However, those who know how to chart the face of the heavens in the proper constellations can arrange not only the symbols but all their works, both of art and of nature, according to the power of the heavens. But, because it is difficult to gain certainty about the heavenly bodies, there is a great deal of error among many men in these matters, and there are few who know how to order things usefully and truly. For that reason, the mob of mathematicians judging and operating by the great stars does not get very far nor accomplish anything useful, while the skilled, those having sufficient command of the art, can accomplish many useful things, both by judgments and by works at auspicious times.

Nevertheless, one should consider that the skilled physician, and whoever else must arouse the soul, can (according to Constantine the Physician) usefully apply incantations and signs, albeit false ones; not because the signs and incantations themselves achieve anything, but in order that the patient take his medicine more faithfully and willingly, that his spirit be awakened, and that he have deeper trust, hope, and joy. An aroused soul can renew much in its own body, so that by joy and confidence the patient convalesces from sickness to health. Therefore (if we believe Constantine the Physician), it is not to be abhorred if, in order to arouse a patient to hope and confidence in health, a physician should do something of this sort to magnify his work, though not for purposes of deceit or for its own value. For Constantine himself, in his Letter on Things Hung About the Neck thus concedes incantations and symbols to the neck and defends them in this case. For the soul has, through its strong affections, great power over its body, as Avicenna teaches in his commentary on On the Soul IV and On Animals VIII; and all wise men agree. That is why plays are performed and pleasing things brought before the sick. Indeed, many contraries sometimes yield to the appetite, because the will and desire of the soul wins over sickness.

Chapter III: On the power of speech and the refutation of magic

Because the truth never hurts, we must consider most carefully that every agent extends its power and species from itself to external matter; not only substances do this but also active accidents of the third type of quality. Things extend some sensible and some insensible powers. Hence man, since he is nobler than all other corporeal things, most extends his power and species beyond himself. Primarily he does so due to his rational soul, but nonetheless spirits and heats emanate from him as they do from other animals. We see that other animals change and alter things exposed to them, as for example, the basilisk kills by sight alone, and the wolf renders the sound of humans if he seesa man first, and the hyena does not permit a dog to bark within his shadow, as Solinus in his On the Wonders of the World, and other authors, relate. And Aristotle in his book On Vegetables says that the fruit of the female palm tree matures by the odor of the male; and in some regions mares are impregnated by the odor of stallions, as Solinus relates. Many such things, and many more marvelous ones (as Aristotle teaches in his Book of Secrets), take place through the species and powers of plants and animals. Since, therefore, plants and animals cannot attain to the dignity of human nature, man can far more extend his powers and species and emit heat to alter bodies outside him: witness Aristotle in On Waking and Sleeping II, who says that if a woman in menstruation should loo into a mirror she will infect it and bloody clouds will appear in it. And Solinus tells us that in the region of Scythia there are women "who have double pupils in one eye"; whence Ovid writes, "The double pupil does harm."

When such women become angry they kill men simply by looking at them. And we know that a man in bad health, having a contagious disease such as leprosy, falling sickness, acute fever, diseased eyes, or something of the sort, infects and contaminates others present. Conversely, healthy men of good complexion and extreme youthfulness comfort others and men enjoy their presence. This is due to the soothing spirits, healthy and pleasing vapors, good natural heat, and species and powers that they exude, as Galen teaches in his Tegni. And the evil increases if the soul is corrupted by many great sins, and if there is strong thought and eager desire to do injury and evil. For then the nature of health and sickness obeys the thoughts of the soul and its desires and acts more strongly. Whence the leper who from strong desire and thought and an eager solicitude seeks to infect another person present will infect him all the more quickly and strongly than if he did not think, desire, or try to do so. For, as Avicenna teaches in the aforesaid book, the nature of the body obeys the thoughts and vehement desires of the soul. Indeed, no work of man takes place unless the natural power in his limbs obeys the thoughts and desires of the soul. For, as Avicenna teaches in Metaphysics III, thought is the first mover and then desire in conformity with thought, and afterward natural force in the limbs, which obeys thought and desire. As has been said, this is true in a similar way for good and for evil.

When, therefore, such things are found in a man as good health, strength of body, youth, beauty, elegance of limb, a soul free of sins, a strong mind, and eager desire to do some great work, then whatever can be done through the power and species of man, and through his spirits and natural heat, will necessarily be done more strongly and more eagerly by species, spirits, vapors, and influences of this sort than if any of these is lacking.

This is especially the case if strong desire and valid intention are not lacking. Therefore, when all the said causes join together, some things can take place through the words and works of man. For words result from inside through the thoughts and desires of the soul, by the motions of the spirits, the natural heat, and the vocal artery. And the generation of words has open paths through which there is a great exit of spirits, heat, evaporations, powers, and species which can be produced by the soul and the heart. Hence changes from the other spiritual parts are brought about through words, as befits them through the power of nature. For we see that through such open paths from the heart and the interior, exhalations, sighs, and many releasings of spirits and of heat take place, which sometimes do harm when they come from an infirm and unhealthy body, and sometimes do good and comfort when they are produced by a clean, strong, healthy body. And hence in a similar way some great natural operations can be carried out by the generation and speaking of words with the intention and desire to do works.

Whence it is worth noting that the live voice has great powers; not because it has the power the magicians feign for doing and changing in a similar way (as they imagine) but rather as we have said, to wit, according to what nature has ordained. Therefore, one really must think carefully in these matters, for it is easy for a man to go wrong, and many do go wrong in one direction or the other, because some deny any working and others grant too much and lean toward magic. Therefore, many books are to be avoided due to incantations, symbols, oaths, conjurations, sacrifices, and things of this sort, because they are purely magical: for example, the book On the Duties of the Spirits, the book On the Death of the Soul, the book On the Notorious Art, and infinitely many like them, which contain the power neither of art nor of nature, but contrivances of magicians. Nonetheless, one should consider that magicians esteem many books that are not of this sort, but contain the dignity of wisdom. The experience of any wise man will teach, therefore, which books are suspect and which not. For, if someone should find in some of them the work of nature and of art, he should accept it; if not, he should leave it as suspect. And just as it is unworthy and illicit of a wise man to deal in magic, so too it is superfluous and unnecessary. For, as Isaac thinks in the book On Fevers, the rational soul is not impeded in its workings unless it is held back by ignorance. As Aristotle would have it in the Book of Secrets, the healthy and good intellect avails of everything necessary to man, albeit with the aid of divine virtue. For he says in Meteorology III that there is no power except through God, and at the end of the Ethics he says that no power, either mortal or natural, is without divine influence. Hence, when we speak of the power of particular agents, we do not exclude the governance of the universal agent and first cause. For every primary cause has greater effect on the thing caused than does a secondary cause, as Aristotle sets forth in the first proposition of On Causes.

Chapter IV: On wondrous artificial instruments

Therefore, I shall now first relate the works of art and of nature to be marveled at, in order then to assign their causes and modes of operation. There is no magic in them, as it would seem that every magical power is inferior to and unworthy of these works. First, those things achieved through the design and reasoning of art alone: Now an instrument for sailed without oarsmen can be produced such that the largest ships, both riverboats and seagoing vessels, can be moved under the direction of a single man at a greater velocity than if they were filled with men. A chariot can be made that moves at an unimaginable speed without horses; such we think to have been the scythe-bearing chariots with which men fought in antiquity. And an instrument for flying can be made, such that a man sits in the middle of it, turning some sort of device by which artificially constructed wings beat the air in the way a flying bird does. And an instrument small in size for raising and lowering almost infinite weights; at times there is nothing more useful than this, for, by an instrument three fingers high and just as wide, or of less size, a man could snatch up himself and his friends and raise and lower them from every danger of prison. Moreover, an instrument could easily be made by which one man could violently draw to himself a thousand men against their will and attract other things in the same way. And instruments can be made for walking in seas and rivers, right down to the bottom, without bodily danger. For Alexander the Great used these to see the secrets of the sea, according to what Ethicus the astronomer says. These things were all made in antiquity, and it is certain they have been made in our times, unless it be the flying machine, which I have not seen, nor do I know anyone who has, though I do know a wise man who has thought of a way to carry out such a device. Almost infinitely many such things can be made, such as bridges that span rivers without pillars or any support, and machines and unheard-of devices.

Chapter V: On artificial optical phenomena

But there are even more philosophical contrivances. For instance, glass mirrors can be so shaped that one thing appears ears to be many, and one man an army, and several suns and moons (or however many we want) appear. For nature sometimes shapes vapors such that two or three suns or moons appear together in the air, as Pliny relates in his Natural History II. For this reason several, or infinitely many, stars can appear in the air, because after going beyond one there is no limit to the number, as Aristotle argues in his chapter on the vacuum (Physics IV?). Thus one can produce infinite terror for any opposing city or army, so that due either to the multiplication of the appearances of the stars or to the multiplication of the men congregated about them, they will despair. Especially if the following teaching is combined with this first one.

For glasses can be so shaped that things placed at the greatest distances appear most near and conversely; so that we could read the most minute letters at an incredible distance, count things however small, and make stars appear where we want. Thus it is thought Julius Caesar on the shores of Gaul discovered by huge mirrors the disposition and locations of the camps and cities of Great Britain.

Moreover, bodies can be so shaped that the largest things appear to be the smallest and conversely, and the highest appear the lowest and conversely, and the hidden appear evident. For thus Socrates found out that a dragon despoiling the city and countryside with his pestilential breath lived in hiding places in the mountains. Thus also everything about opposing cities and armies can be found out by the enemy. Moreover, bodies could be so shaped that poisonous and infectious species and influences could be directed wherever a man might want. For thus Aristotle is said to have taught Alexander, who by this teaching directed the poison of the basilisk erected on the city wall against his army back into the city itself.

Again, mirrors could be so shaped that every man would see gold, silver, precious stones, or whatever a man might want, though whoever hastened to the site of the vision would find nothing. We do not, therefore, have to use magical illusions when the power of philosophy teaches how to bring about what is needed.

It is through designs employing more sublime powers that rays are brought together by various shapes and reflections at any distance we want, where whatever is met is set afire: witness burning mirrors that ignite things in front and in back, as certain authors teach in their books. And the greatest of all designs and designed things is that by which the heavens are described according to their longitudes and latitudes in a solid figure, in which they are moved in daily motion. This would be worth a kingdom to a wise man.

These things suffice as examples of designs, although infinitely many other things could be set forth in daily life to be marveled at.

Chapter VI: On marvelous experiments

Indeed, there are some things connected with these that go beyond design. For [to burn something] at any distance we want, we can artificially compose a burning fire: to wit, from saltpeter and other things, or again from red petroleum oil and other things, or again from malta, and naphtha, and similar things. According to what Pliny says in Book II [Chap. 10] of his Natural History, the city [of Syracuse] so defended itself against the Roman army; for thrown malta burns an armed soldier. Akin to these things is Greek fire and many burning substances. Beyond this one can make perpetual lamps and baths that steam endlessly. For we have known many things that are not consumed by flames, such as the hide of the salamander, and talc and suchlike, which, when something is added, burst into flame and glow but are not burned; rather, they are purified.

Indeed, beyond these there are other wonders of nature. For one can make sounds such as thunder and vibrations in the air, causing greater horror than those which nature makes. For a small amount of adapted material, i.e. the amount of a thumb, makes a horrible sound and produces vehement trembling. This is done in many ways, by which every army and city is destroyed; for example, in the manner of Gideon, who with three hundred men destroyed the infinite army of the Midianites with broken bottles and lamps from which fire burst forth with an unimaginable din. These are wonders if one knows how to use them to the full, [especially] when quantity and material are lacking.

Indeed, there are many wonders of another sort which, though they do not have much utility, nevertheless do make an ineffable show of wisdom and can be applied to proving all occult things, which the inexperienced rabble contradicts; they are similar to the attraction of iron by hard steel (adamas). For who would believe that an attraction of this sort takes place, unless he were to see it? In this attraction of iron are many wonders of nature that are not known by the rabble, just as experience shows the careful observer. But there are more and greater wonders. For similarly there is the attraction of gold, silver, and all metals by a stone. Again, a falling stone runs to acetum (?), and plants to each other, and locally divided parts of animals run together by a natural motion. After I have examined things of this sort, I find nothing difficult to believe when I consider it well, neither among divine things nor among human things.

Yet there are wonders greater than these. For there can be nothing less than the whole power of mathematics in the spherical instrument built according to the design of Ptolemy, in which all things that are in the heavens are described accurately by their longitudes and latitudes. But that it be moved naturally with a diurnal motion is not within the power of the mathematician. Nevertheless, let a faithful and great experimenter sweat to make it out of such material and by such design that the heavens would turn naturally with a diurnal motion (which it would seem possible to do, since many things are carried along by the motion of the celestial bodies, such as comets, the tides, and other things, as a whole or in part): that would be a greater wonder than all the aforementioned ones and would be of almost infinite utility. For then all instruments of astronomy, both the special and the common ones, would be obsolete; nor could it be bought with a king's treasure.

And, although not in terms of a wonder, but in terms of public and private utility, still greater things can be accomplished. For example, a wealth of gold and silver can be brought into circulation, as much as men want, and not only by virtue of their natural occurrence, but also with the complementary help of art. That is, of the seventeen grades of gold, eight derive from the admixture of silver with gold. The first grade consists of sixteen parts of gold with several parts of silver. By adding one degree of gold through the admixture of one of silver, we reach the twenty-second degree of gold. Similarly, there are as many degrees resulting from the admixture of air with gold, so that the ultimate degree consists of twenty four degrees of gold; it is pure, without the admixture of any other metal. Nature cannot proceed farther, as experience teaches. But art can augment gold in degrees of purity ad infinitum; similarly it can perfect silver without deceit.

But greater than the preceding is that, although the rational soul cannot be forced (in that it enjoys free will), it can nevertheless be effectively disposed, excited, and induced to want freely to change its habits, affections, and desires according to the will of another. This is true not only of a single person, but of a whole army, or city, or people of a region. Aristotle gives examples of this in the Book of Secrets, speaking about a region, an army, and a single person. In these things, one almost reaches the final goal of nature and of art.

Chapter VII: On retarding the accidents of old age and prolonging human life

But the ultimate degree to which art complements all the power of nature is the prolongation of human life over a long time. Many experiments show that this is possible. For Pliny recounts in Book XXII that the vigorous soldier remains healthy in body and spirit beyond the usual age of a man. When Octavian Augustus asked him what he should do to live so long, he responded in a riddle, i.e. that he should put oil on the outside and mulsum on the inside (according to the authors, mulsum consists of eight parts of water and nine of honey). But, beyond that, many similar things have happened. A farmer plowing in the fields found x a golden vessel containing a noble liquor and, thinking it the water of heaven, he washed his face and drank. Renewed in body and spirit and goodness of wisdom, he rose from ploughman to servant of the King of Sicily; this happened in the time of Ring William. It is also well verified by the testimony of papal letters that some German captured by the Saracens received a medicine by which his life was extended by fifty years. For the king who held him captive had received the messengers of a great king with this medicine but, because he held it suspect, he wanted to test it on a captive who had been brought to him. Similarly the mistress of Nemore in Great Britain, seeking a white stag, found an unguent, which the warden of the forest spread all over his body, except for the soles of his feet. He lived for thirty years without aging, except for foot trouble. And quite often T have experienced in our times that countryfolk have lived one hundred and sixty years or thereabouts, without the aid of doctors. These things are also confirmed by the behavior of animals. Stags, eagles, serpents, and many others renew their youth by the powers of herbs and stones. Hence, urged on by the examples of brutes, wise men devoted themselves to this sort of secret, judging that what was granted brute animals was possible for man. For this reason, Artephius, having in his wisdom sought out the secret powers of animals, stones, herbs, and other things for the sake of knowing the secrets of nature and most of all for the sake of long life, prided himself on having lived 1025 years.

The possibility of prolonging life is also evidenced by the fact that man is naturally immortal and unable to die, and that even after sin he could still live about a thousand years, and that thereafter the length of life was gradually shortened. Therefore it is necessary that this sort of shortening be accidental, whence it might be remediable, in whole or in part. But if we want to investigate the accidental cause of this corruption, we shall find that it is not from heaven, or from anything other than a defect in the regimen of health. For, to the extent that the fathers are corrupted, they generate sons of corrupt health and constitution, and the suns are corrupted by the same cause. Thus corruption passes from the fathers to the sons, until the shortening of life steadily prevails, as is the case today. Nevertheless it does not follow from this that it will always be shortened to less and less, because a limit has been set for the human race, so that men usually live eighty years, "but their travail and pain are greater" [Psalm 90]. Anyone, then, would have a remedy against his own corruption, if he were to carry out a complete regimen of health from youth, which consists of food, drink, sleep, waking, motion, rest, evacuation, retention, air, passion of the soul. For if someone were to maintain this regimen from birth, he would live as long as the nature inherited from his parents would permit and would be led to the final limit of that nature diminished by original justice; he could not, however, go beyond the limit, because this regimen provides no remedy against the old corruption of the parents. But it is impossible that a man would thus be ruled in all moderation of these things, as the regimen of health demands. Hence, the shortening of life necessarily takes place for this reason, and not only because of the corruption of the parents.