NOR shall it any ways detract from the just reputation of this famous sect, that its rise and institution are owing to such an author as I have described Jack to be, a person whose intellectuals were overturned, and his brain shaken out of its natural position; which we commonly suppose to be a distemper, and call by the name of madness or phrenzy. For, if we take a survey of the greatest actions that have been performed in the world, under the influence of single men, which are the establishment of new empires by conquest, the advance and progress of new schemes in philosophy, and the contriving, as well as the propagating, of new religions, we shall find the authors of them all to have been persons whose natural reason had admitted great revolutions from their diet, their education, the prevalency of some certain temper, together with the particular influence of air and climate. Besides, there is something individual in human minds, that easily kindles at the accidental approach and collision of certain circumstances, which, though of paltry and mean appearance, do often flame out into the greatest emergencies of life. For great turns are not always given by strong hands, but by lucky adaption, and at proper seasons; and it is of no import where the fire was kindled, if the vapour has once got up into the brain. For the upper region of man is furnished like the middle region of the air; the materials are formed from causes of the widest difference, yet produce at last the same substance and effect. Mists arise from the earth, steams from dunghills, exhalations from the sea, and smoke from fire; yet all clouds are the same in composition as well as consequences, and the fumes issuing from a jakes will furnish as comely and useful a vapour as incense from an altar. Thus far, I suppose, will easily be granted me; and then it will follow, that as the face of nature never produces rain but when it is overcast and disturbed, so human understanding, seated in the brain, must be troubled and overspread by vapours, ascending from the lower faculties to water the invention and render it fruitful. Now, although these vapours (as it hath been already said) are of as various original as those of the skies, yet the crop they produce differs both in kind and degree, merely according to the soil. I will produce two instances to prove and explain what I am now advancing.
A certain great prince  raised a mighty army, filled his coffers with infinite treasures, provided an invincible fleet, and all this without giving the least part of his design to his greatest ministers or his nearest favourites. Immediately the whole world was alarmed; the neighbouring crowns in trembling expectation towards what point the storm would burst; the small politicians everywhere forming profound conjectures. Some believed he had laid a scheme for universal monarchy; others, after much insight, determined the matter to be a project for pulling down the pope, and setting up the reformed religion, which had once been his own. Some, again, of a deeper sagacity, sent him into Asia to subdue the Turk, and recover Palestine. In the midst of all these projects and preparations, a certain state-surgeon, gathering the nature of the disease by these symptoms, attempted the cure, at one blow performed the operation, broke the bag, and out flew the vapour; nor did anything want to render it a complete remedy, only that the prince unfortunately happened to die in the performance. Now, is the reader exceeding curious to learn from whence this vapour took its rise, which had so long set the nations at a gaze? What secret wheel, what hidden spring could put into motion so wonderful an engine? It was afterwards discovered that the movement of this whole machine had been directed by an absent female, whose eyes had raised a protuberancy, and before emission, she was removed into an enemy's country. What should an unhappy prince do in such ticklish circumstances as these? He tried in vain the poet's neverfailing receipt of corpora quoque; for
Idque petit corpus mens unde est saucia amore;Having to no purpose used all peaceable endeavours, the collected part of the semen, raised and inflamed, became adust, converted to choler, turned head upon the spinal duct, and ascended to the brain. The very same principle that influences a bully to break the windows of a whore who has jilted him, naturally stirs up a great prince to raise mighty armies, and dream of nothing but sieges, battles, and victories.
Unde feritur, eo tendit, gestitq: coire._LUCR.
---- Teterrima belliThe other instance  is what I have read somewhere in a very ancient author, of a mighty king, who, for the space of above thirty years, amused himself to take and lose towns, beat armies, and be beaten, drive princes out of their dominions; fright children from their bread and butter; burn, lay waste, plunder, dragoon, massacre subject and stranger, friend and foe, male and female. `Tis recorded, that the philosophers of each country were in grave dispute upon causes natural, moral, and political, to find out where they should assign an original solution of this phenomenon. At last the vapour or spirit, which animated the hero's brain, being in perpetual circulation, seized upon that region of the human body, so renowned for furnishing the zibeta occidentalis,  and gathering there into a tumor, left the rest of the world for that time in peace. Of such mighty consequence it is where those exhalations fix, and of so little from whence they proceed. The same spirits which, in their superior progress would conquer a kingdom, descending upon the anus, conclude in a fistula.
Let us next examine the great introducers of new schemes in philosophy, and search till we can find from what faculty of the soul the disposition arises in mortal man, of taking it into his head to advance new systems with such an eager zeal, in things agreed on all hands impossible to be known; from what seeds this disposition springs, and to what quality of human nature these grand innovators have been indebted for their number of disciples. Because, it is plain, that several of the chief among them, both ancient and modern, were usually mistaken by their adversaries, and indeed by all except their own followers, to have been persons crazed, or out of their wits, having generally proceeded in the common course of their words and actions by a r method very different from the vulgar dictates of unrefined reason; agreeing for the most part in their several models, with their present undoubted successors in the academy of modern Bedlam (whose merits and principles I shall farther examine in due place). Of this kind were Epicurus, Diogenes, Apollonius, Lucretius, Paracelsus, Descartes, and others, who, if they were now in the world, tied fast, and separate from their followers, would, in this our undistinguishing age, incur manifest danger of phlebotomy, and whips, and chains, and dark chambers, and straw. For what man in the natural state or course of thinking, did ever conceive it in his power to reduce the notions of all mankind exactly to the same length, and breadth, and height of his own? Yet this is the first humble and civil design of all innovators in the empire of reason. Epicurus modestly hoped, that one time or other's certain fortuitous concourse of all men's opinions, after perpetual justlings, the sharp with the smooth, the light and the heavy, the round and the square, would by certain clinamina unite in the notions of atoms and void, as these did in the originals of all things. Cartesius reckoned to see before he died the sentiments of all philosophers, like so many lesser stars in his romantic system, wrapped and drawn within his own vortex. Now, I would gladly be informed, how it is possible to account for such imaginations as these in particular men without recourse to my phenomenon of vapours, ascending from the lower faculties to overshadow the brain, and thence distilling into conceptions for which the narrowness of our mother-tongue has not yet assigned any other name besides that of madness or phrenzy. Let us therefore now conjecture how it comes to pass, that none of these great prescribers do ever fail providing themselves and their notions with a number of implicit disciples. And, I think, the reason is easy to be assigned: for there is a peculiar string in the harmony of human understanding, which in several individuals is exactly of the same tuning. This, if you can dexterously screw up to its right key, and then strike gently upon it, whenever you have the good fortune to light among those of the same pitch, they will, by a secret necessary sympathy, strike exactly at the same time. And in this one circumstance lies all the skill or luck of the matter; for if you chance to jar the string among those who are either above or below your own height, instead of subscribing to your doctrine, they will tie you fast, call you mad, and feed you with bread and water. It is therefore a point of the nicest conduct to distinguish and adapt this noble talent, with respect to the differences of persons and of times. Cicero understood this very well, when writing to a friend in England, with a caution, among other matters, to beware of being cheated by our hackney-coachmen (who, it seems, in those days were as arrant rascals as they are now) has these remarkable words: Est quod gaudeas te in ista loca senisse, ubi aliquid sapere viderere.  For, to speak a bold truth, it is a fatal miscarriage so ill to order affairs, as to pass for a fool in one company, when in another you might be treated as a philosopher. Which I desire some certain gentlemen of my acquaintance to lay up in their hearts, as a very seasonable innuendo.
This, indeed, was the fatal mistake of that worthy gentleman, my most ingenious friend, Mr. Wotton: a person, in appearance ordained for great designs, as well as performances; whether you will consider his notions or his looks. Surely no man ever advanced into the public with fitter qualifications of body and mind, for the propagation of a new religion. Oh, had those happy talents misapplied to vain philosophy been turned into their proper channels of dreams and visions, where distortion of mind and countenance are of such sovereign use, the base detracting world would not then have dared to report that something is amiss, that his brain hath undergone an unlucky shake; which even his brother modernists themselves, like ungrates, do whisper so loud, that it reaches up to the very garret I am now writing in.
Lastly, whosoever pleases to look into the fountains of enthusiasm, from whence, in all ages, have eternally proceeded such fattening streams, will find the springhead to have been as troubled and muddy as the current. Of such great emolument is a tincture of this vapour, which the world calls madness, that without its help, the world would not only be deprived of those two great blessings, conquests and systems, but even all mankind would unhappily be reduced to the same belief in things invisible. Now, the former postulatum being held, that it is of no import from what originals this vapour proceeds, but either in what angles it strikes and spreads over the understanding, or upon what species of brain it ascends; it will be a very delicate point to cut the feather, and divide the several reasons to a nice and curious reader, how this numerical difference in the brain can produce effects of so vast a difference from the same vapour, as to be the sole point of individuation between Alexander the Great, Jack of Leyden, and Monsieur Des Cartes. The present argument is the most abstracted that ever I engaged in; it strains my faculties to their highest stretch; and I desire the reader to attend with utmost perpensity for I now proceed to unravel this knotty point. There is in mankind a certain 
And this I take to be a clear solution of the matter.
Having therefore so narrowly passed through this intricate difficulty, the reader will, I am sure, agree with me in the conclusion, that if the moderns mean by madness, only a disturbance or transposition of the brain, by force of certain vapours issuing up from the lower faculties, then has this madness been the parent of all those mighty revolutions that have happened in empire, in philosophy, and in religion. For the brain, in its natural position and state of serenity, disposeth its owner to pass his life in the common forms, without any thought of subduing multitudes to his own power, his reasons, or his visions; and the more he shapes his understanding by the pattern of human learning, the less he is inclined to form parties after his particular notions, because that instructs him in his private infirmities, as well as in the stubborn ignorance of the people. But when a man's fancy gets astride on his reason, when imagination is at cuffs with the senses, and common understanding, as well as common sense, is kicked out of doors, the first proselyte he makes is himself; and when that is once compassed, the difficulty is not so great in bringing over others; a strong delusion always operating from without as vigorously as from within. For, cant and vision are to the ear and the eye, the same that tickling is to the touch. Those entertainments and pleasures we most value in life, are such as dupe and play the wag with the senses. For, if we take an examination of what is generally understood by happiness, as it has respect either to the understanding or the senses, we shall find all its properties and adjuncts will herd under this short definition, that it is a perpetual possession of being well deceived. And first, with relation to the mind or understanding, 'tis manifest what mighty advantages fiction has over truth; and the reason is just at our elbow, because imagination can build nobler scenes, and produce more wonderful revolutions than fortune or nature will be at expense to furnish. Nor is mankind so much to blame in his choice thus determining him, if we consider that the debate merely lies between things past and things conceived; and so the question is only this --- whether things that have place in the imagination, may not as properly be said to exist, as those that are seated in the memory, which may be justly held in the affirmative, and very much to the advantage of the former, since this is acknowledged to be the womb of things, and the other allowed to be no more than the grave. Again, if we take this definition of happiness, and examine it with reference to the senses, it will be acknowledged wonderfully adapt. How fading and insipid do all objects accost us, that are not conveyed in the vehicle of delusion? How shrunk is everything, as it appears in the glass of nature? So that if it were not for the assistance of artificial mediums, false lights, refracted angles, varnish, and tinsel, there would be a mighty level in the felicity and enjoyments of mortal men. If this were seriously considered by the world, as I have a certain reason to suspect it hardly will, men would no longer reckon among their high points of wisdom, the art of exposing weak sides, and publishing infirmities; an employment, in my opinion, neither better nor worse than that of unmasking, which I think has never been allowed fair usage, either in the world or the play-house.
In the proportion that credulity is a more peaceful possession of the mind than curiosity; so far preferable is that wisdom, which converses about the surface, to that pretended philosophy which enters into the depth of things, and then comes gravely back with informations and discoveries, that in the inside they are good for nothing. The two senses, to which all objects first address themselves, are the sight and the touch; these never examine farther than the colour, the shape, the size, and whatever other qualities dwell, or are drawn by art upon the outward of bodies; and then comes reason officiously with tools for cutting, and opening, and mangling, and piercing, offering to demonstrate, that they are not of the same consistence quite through. Now, I take all this to be the last degree of perverting nature; one of whose eternal laws it is, to put her best furniture forward. And therefore, in order to save the charges of all such expensive anatomy for the time to come, I do here think fit to inform the reader, that in such conclusions as these, reason is certainly in the right, and that in most corporeal beings, which have fallen under my cognizance, the outside hath been infinitely preferable to the in; whereof I have been farther convinced from some late experiments. Last week I saw a woman flayed, and you will hardly believe how much it altered her person for the worse. Yesterday I ordered the carcass of a beau to be stripped in my presence, when we were all amazed to find so many unsuspected faults under one suit of clothes. Then I laid open his brain, his heart, and his spleen; but I plainly perceived at every operation, that the farther we proceeded, we found the defects increase upon us in number and bulk; from all which, I justly formed this conclusion to myself; that whatever philosopher or projector can find out an art to sodder and patch up the flaws and imperfections of nature, will deserve much better of mankind, and teach us a more useful science, than that so much in present esteem, of widening and exposing them (like him who held anatomy to be the ultimate end of physic). And he, whose fortunes and dispositions have placed him in a convenient station to enjoy the fruits of this noble art; he that can with Epicurus content his ideas with the films and images that fly-off upon his senses from the superficies of things; such a man truly wise, creams off nature, leaving the sour and the dregs for philosophy and reason to lap up. This is the sublime and refined point of felicity, called, the possession of being well deceived; the serene peaceful state of being a fool among knaves.
But to return to madness. It is certain, that according to the system I have above deduced, every species thereof proceeds from a redundancy of vapours; therefore, as some kinds of phrenzy give double strength to the sinews, so there are of other species, which add vigor, and life, and spirit to the brain. Now, it usually happens, that these active spirits, getting possession of the brain, resemble those that haunt other waste and empty dwellings, which for want of business, either vanish, and carry away a piece of the house, or else stay at home and fling it all out of the windows. By which are mystically displayed the two principal branches of madness, and which some philosophers not considering so well as I, have mistook to be different in their causes, over-hastily assigning the first to deficiency, and the other to redundance.
I think it therefore manifest, from what I have here advanced, that the main point of skill and address is to furnish employment for this redundancy of vapour, and prudently to adjust the season of it; by which means it may certainly become of cardinal and catholic emolument in a commonwealth. Thus one man, choosing a proper juncture, leaps into a gulf, from thence proceeds a hero, and is called the saver of his country; another achieves the same enterprise, but unluckily timing it, has left the brand of madness fixed as a reproach upon his memory; upon so nice a distinction are we taught to repeat the name of Curtius with reverence and love, that of Empedocles with hatred and contempt. Thus also it is usually conceived, that the elder Brutus only personated the fool and madman for the good of the public; but this was nothing else than a redundancy of the same vapour long misapplied, called by the Latins, ingenium par negotiis; or (to translate it as nearly as I can) a sort of phrenzy, never in its right element, till you take it up in business of the state.
Upon all which, and many other reasons of equal weight, though not equally curious, I do here gladly embrace an opportunity I have long sought for, of recommending it as a very noble undertaking to Sir Edward Seymour, Sir Christopher Musgrave, Sir John Bowls, John How, Esq., and other patriots concerned, that they would move for leave to bring in a bill for appointing commissioners to inspect into Bedlam, and the parts adjacent; who shall be empowered to send for persons, papers, and records, to examine into the merits and qualifications of every student and professor, to observe with utmost exactness their several dispositions and behaviour, by which means, duly distinguishing and adapting their talents, they might produce admirable instruments for the several offices in a state, ____ , civil, and military, proceeding in such methods as I shall here humbly propose. And I hope the gentle reader will give some allowance to my great solicitudes in this important affair, upon account of that high esteem I have ever borne that honourable society, whereof I had some time the happiness to be an unworthy member.
Is any student tearing his straw in piece-meal, swearing and blaspheming, biting his grate, foaming at the mouth, and emptying his piss-pot in the spectators' faces? Let the right worshipful the commissioners of inspection give him a regiment of dragoons, and send him into Flanders among the rest. Is another eternally talking, sputtering, gaping, bawling, in a sound without period or article? What wonderful talents are here mislaid! Let him be furnished immediately with a green bag and papers, and threepence in his pocket, and away with him to Westminster Hall. You will find a third gravely taking the dimensions of his kennel, a person of foresight and insight, though kept quite in the dark; for why, like Moses, ecce cornuta erat ejus facies. He walks duly in one pace, entreats your penny with due gravity and ceremony, talks much of hard times, and taxes, and the whore of Babylon, bars up the wooden window of his cell constantly at eight o'clock, dreams of fire, and shoplifters, and court-customers, and privileged places. Now, what a figure would all these acquirements amount to, if the owner were sent into the city among his brethren! Behold a fourth, in much and deep conversation with himself, biting his thumbs at proper junctures, his countenance checkered with business and design, sometimes walking very fast, with his eyes nailed to a paper that he holds in his hands; a great saver of time, somewhat thick of hearing, very short of sight, but more of memory; a man ever in haste, a great hatcher and breeder of business, and excellent at the famous art of whispering nothing; a huge idolator of monosyllables and procrastination, so ready to give his word to everybody, that he never keeps it; one that has forgot the common meaning of words, but an admirable retainer of the sound; extremely subject to the looseness, for his occasions are perpetually calling him away. If you approach his grate in his familiar intervals, 'Sir,' says he, 'give me a penny, and I'll sing you a song; but give me the penny first.' (Hence comes the common saying, and commoner practice of parting with money for a song.) What a complete system of court skill is here described in every branch of it, and all utterly lost with wrong application. Accost the hole of another kennel, first stopping your nose, you will behold a surly, gloomy, nasty, slovenly mortal, raking in his own dung, and dabbling in his urine. The best part of his diet is the reversion of his own ordure, which expiring into steams, whirls perpetually about, and at last re-infunds. His complexion is of a dirty yellow, with a thin scattered beard, exactly agreeable to that of his diet upon its first declination, like other insects, who having their birth and education in an excrement, from thence borrow their colour and their smell. The student of this apartment is very sparing of his words, but somewhat over-liberal of his breath; he holds his hand out ready to receive your penny, and immediately upon receipt withdraws to his former occupations. Now, is it not amazing to think, the society of Warwick-lane should have no more concern for the recovery of so useful a member, who, if one may judge from these appearances, would become the greatest ornament to that illustrious body? Another student struts up fiercely to your teeth, puffing with his lips, half squeezing out his eyes, and very graciously holds you out his hand to kiss. The keeper desires you not to be afraid of this professor, for he will do you no hurt; to him alone is allowed the liberty of the antechamber, and the orator of the place gives you to understand, that this solemn person is a tailor run mad with pride. This considerable student is adorned with many other qualities, upon which, at present, I shall not farther enlarge - - - - - - Hark in your ear  - - - - - I am strangely mistaken, if all his address, his motions, and his airs, would not then be very natural, and in their proper element.
I shall not descend so minutely, as to insist upon the vast number of beaux, fiddlers, poets, and politicians, that the world might recover by such a reformation; but what is more material, besides the clear gain redounding to the commonwealth, by so large an acquisition of persons to employ, whose talents and acquirements, if I may be so bold as to affirm it, are now buried, or at least misapplied; it would be a mighty advantage accruing to the public from this inquiry, that all these would very much excel, and arrive at great perfection in their several kinds; which, I think, is manifest from what I have already shown, and shall enforce by this one plain instance, that even I myself, the author of these momentous truths, am a person, whose imaginations are hard-mouthed, and exceedingly disposed to run away with his reason, which I have observed from long experience to be a very light rider, and easily shook off; upon which account, my friends will never trust me alone, without a solemn promise to vent my speculations in this, or the like manner, for the universal benefit of human kind; which perhaps the gentle, courteous, and candid reader, brimful of that modern charity and tenderness usually annexed to his office, will be very hardly persuaded to believe.
1 This was Harry the Great of France.
2 Ravillac, who stabbed Henry the Great in his coach.
3 This is meant of the present French king. [From Swift's 1720 edition: "Lewis XIV."cited in Guthkelch & Smith, p. 165. -Singh, 1996.]
4 Paracelsus, who was so famous for chemistry, tried an experiment upon human excrement, to make a perfume of it, which when he had brought to perfection, he called zibeta occidentalis, or western-civet, the back parts of man (according to his division mentioned by the author, Section VIII )being the west.
5 Epist. ad Fam. Trebatio.
6 Here is another defect in the manuscript, but I think the author did wisely, and that the matter which thus strained his faculties, was not worth a solution; and it were well if all metaphysical cobweb problems were no otherwise answered.
8 A lawyers' coach-hire.
9 Cornutus is either horned or shining, and by this term, Moses is described in the vulgar Latin of the Bible.
10 I cannot conjecture what the author means here, or how this chasm could be filled, tho' it is capable of more than one interpretation.