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Source: Extracts from the Introduction to Petty's The Economic Writings of Sir William Petty, together with The Observations upon Bills of Mortality, more probably by Captain John Graunt, ed. Charles Henry Hull (Cambridge University Press, 1899), vol. 1.
William Petty was born on Monday, 26 May, 1623, at the house of his father, a poor clothier of Romsey in Hampshire.
According to the detailed account of his childhood which he gave to Aubrey, his chief amusement consisted in “looking on the artificers, e.g. smyths, the watchmaker, carpenters, joiners, etc.” until he “could have worked at any of their trades.” “At twelve years of age he had acquired a competent smattering of Latin,” and before his sixteenth year he was well advanced in Greek, mathematics and navigation. It was, perhaps, in his fourteenth year that Petty was overtaken by an accident which gave him opportunity to turn his precocity to good account. After some ten months' service as cabin boy on an English merchantman, he had the misfortune to break his leg. Hereupon the crew set him ashore on the French coast, not far from Caen. The unhappy lad, thus left to shift for himself, recounted his misfortunes in Latin so excellent that the Jesuit fathers of that city not only cared for him but straightway admitted him a pupil of their college . Here he prosecuted his former studies and incidentally learned the French language as well. Meanwhile he supported himself in part by teaching navigation to a French officer and English to a gentleman who desired to visit England—Latin serving, apparently, as the medium of communication in both cases—and in part by traffic in “pittiful brass things with cool'd glasse in them instead of diamonds and rubies.” Upon his return to England he appears to have spent some months in the Royal Navy, but in 1643, “when the civil war betwixt the King and Parliament grew hot,” he joined the army of English refugees in the Netherlands and “vigorously followed his studies, especially that of medicine,” at Utrecht, Leyden and Amsterdam. By November, 1645, he had made his way to Paris where he continued his anatomical studies, reading Vesalius with Hobbes and forming many acquaintances in the group of scholars that gathered around Father Mersen and the Marquis of Newcastle. In the following year he returned to Romsey, and appears to have taken up for a time the business formerly carried on by his father . At Romsey he busied himself also with an instrument for double writing, which he had so far completed by March, 1647, that a patent upon it was then granted him for a term of seventeen years. In November, if not earlier, he went to London with the intention of selling this device . His expectations were not realized, and it may be inferred from his subsequent remarks upon patent monopolies that his career as an inventor proved far from gainful. In London Petty was “admitted into several clubbs of the virtuosi,” and secured the friendship, among others, of Milton's friend, Samuel Hartlib, to whom he addressed the “Advice of W. P. for the Advancement of some Particular Parts of Learning .” It was upon Hartlib's encouragement, also, that he began his abortive “History of Trades .”
In 1648 Petty removed from London to Oxford, where the University had been recently reorganized by the parliamentary party. He was soon made deputy to Clayton, the professor of anatomy, and succeeded him in January, 1650, “Dr Clayton resigning his interest” in the professorship “purposely to serve him.” Meanwhile he had become a doctor of medicine and a fellow of Brasenose College , and, in December, 1650, had added to his reputation by participating in the reanimation of one Ann Green, a wench hanged at Oxford for the supposed murder of her child . At about the same time he was chosen vice-principal of Brasenose and professor of music in Gresham College. The vice-principalship he retained until 9 August, 1659, the Gresham professorship until 8 March, 1660 . In April, 1651, the visitors to the University had granted him the unusual favour of two years’ leave of absence, with an allowance of £30 per annum . The occasion of this grant and the nature of his occupation during the next few months are unknown; Lord Edmond Fitzmaurice conjectures that he travelled. However that may be, there soon came to him an appointment which exercised a determining influence upon the entire course of his subsequent life; he was made physician to the army in Ireland and to the family and person of the Lieutenant-General. Thenceforward his chief interests, both material and intellectual, were intimately connected with affairs beyond St George's Channel.
As physician to the army Petty resided in Ireland nearly seven years, returning to England in 1659 as the bearer of Henry Cromwell's letter of acquiescence in the government set up by the Rump. It was during this first period of his Irish residence that he made the “Down Survey” of Ireland , a work which laid the foundation of his fortune and constituted his earliest title to fame. After the suppression of the Irish rebellion of 1641 the government prepared to distribute the forfeited lands of the rebels, one moiety among the soldiers of the victorious army, the other among the adventurers who, under the provisions of 17 Car. I., c. 34, had advanced money for the army's support. As a preliminary to the proposed distribution, it was necessary that the situation and area of the forfeited holdings be determined. When Petty first reached Ireland he found a survey for this purpose already in progress. He soon concluded that this survey was being “most insufficiently and absurdly managed” by its director, one Benjamin Worsley, and he promptly proposed to make a more satisfactory survey himself . This he promised to complete, duly set down in maps and books, within a year and a month. After much discussion his proposals were accepted, 11 December, 1654, but the time for the completion of the survey was afterwards extended to thirteen months from February, 1655. Petty thus agreed to measure and record, on a scale of forty perches to an inch, all forfeited lands, profitable and unprofitable, set aside for the satisfaction of the officers and soldiers,—the so-called “army lands”—down to the smallest recognized civil denominations. He also undertook to survey and map, for general use and upon a smaller scale, the bounds of all baronies, whether forfeited or not, in all counties which contained forfeited lands. By March, 1656, the survey of the army lands was virtually completed, and he applied to the Council for payment and for release from his bond. His work was referred to a committee representing the army and was by them pronounced satisfactory. Worsley, on the contrary, pointed out a number of minor errors. These were such, in Petty's view, as should “bee not charged uppon” him “as faults” but rather such accidents and disasters as ever attend vast and variable undertakings .” Nevertheless he attempted a detailed answer to Worsley's objections. General Larcom, a judge eminently competent, declares that he met the charges “satisfactorily, indeed triumphantly: for whatever shortcomings or blemishes might be detected in so great a work, performed with such extraordinary rapidity, over so great an extent of country at the same time, there can be no doubt that, on the whole, it exceeded the articles of agreement, and that the delay which will be seen to have taken place in the payment, was vexatious and unjust.” Nevertheless Petty was obliged to wage a prolonged contest for his rights, the final order for his payment being postponed until March, 1657, while his bond was not released until December of the same year. The publication of the results of the general survey, on the other hand, appears to have been delayed for several years .
The completion of the Down Survey of the army lands by no means concluded Petty's “services and sufferings” in Ireland. On the 7th July, 1656, he was named a member of the commission to distribute among the officers and soldiers the forfeited lands which he had surveyed. Vincent Gookin, one of his associates on the commission, presently departed for England to attend Parliament, and fear of offending military friends deterred the other member, Major Miles Symner, from taking an active part in its labours . Petty was therefore, obliged, “to manage the executive part of that vast and intricate work, as if it were alone, Few other Commissioners (for fear of falling into some Error) adventuring to do business without” him, “Whereby all displeasures real or imaginary, were accounted not onely” his “Permission but Commission: Not onely” his “simple Act, but design, contrivance and revenge .” Working thus single-handed, he set out their lands to the army with such dispatch that the distribution was completed in February, 1657. Meanwhile he had begun, in conjunction with Worsley, a survey of the adventurers’ moiety of the forfeited lands. Distribution based upon this survey was delayed by disagreements among the adventurers at London until finally, in May, 1658, the patience of the Lord Deputy was exhausted by their indecision and he sent Petty to treat with them for the appointment of a commission which should adjust their claims out of hand. Upon his arrival in London, Petty found the adventurers already in receipt of an anonymous communication from Dublin, alleging that he intended if possible to cheat them as, it was charged, he had cheated the army. In the face of this charge he won the entire confidence of the adventurers’ committee, and was provided by them with a petition to the Council at Dublin requesting “that, instead of all the said Commissioners, Dr Petty alone may bee authorized and approved by your Lordshipps, to act as well in behalfe of your Lordshipps as the adventurers, as a person best able to give the business a dispatch .” The news of his triumph at London stirred up Petty's enemies at Dublin to prepare a second letter—Petty called it a libel —directed ostensibly to the adventurers and assuring them that his dishonesty in surveying and setting out the army lands had gone unpunished only because of his position as a clerk of the Council and prime favourite of the Lord Deputy. By prearrangement this letter was intercepted on its way to London and was brought to the attention of Henry Cromwell. Cromwell, whose confidence in Petty never wavered, at once referred the charges to a committee of seven officers. “Whilst these things were doeing in Ireland, the doctor rides night and day from London, in the end of December , and through many hazards comes to Dublyn, God having kept him safe in the greatest storme that ever was knowne, as he thankfully construed it, to preserve him for his vindication.” At Petty's request the officers’ committee already appointed was increased by the addition of “the Receiver-General, Auditors-General, and one Mr Jeoffryes, a person well reputed for his integrity and skill in accompts, that, having given a satisfactory accompt unto these able and proper ministers of the State, he might all under one bee discharged both from the State and armyes further question or suspicion.” A majority of the committee as thus constituted declared the charges to be without foundation. Three of the officers, a minority of the original committee, for a time dissented from this finding, but eventually, affecting to believe that in a new attack brought against Petty from an unexpected quarter “his Excellency himselfe was strucke att,” they declined to “muddle or make further in the business.”
The scruples of the officers in Ireland were by no means groundless. The death of the Lord Protector had reanimated the purely parliamentarian party of the army in England to an activity that boded no good to his sons. Petty was, throughout his life, a firm supporter of the family of Cromwell, and it was as Henry Cromwell's friend that he had been elected member for West Looe in Richard's parliament. It is not surprising, therefore, that the charges of bribery and breach of trust now preferred against him in the House of Commons by Sir Jerome Sanchey should have appeared to the officers at Dublin as a blow struck at the Lord Deputy himself. A letter from speaker Bampfield brought Sanchey's charges to Petty's attention: On the day set for his reply he appeared in the House and defended himself with great moderation. The charges were vague and there was no proof. In so extensive and difficult a work as the distribution of the army's lands it was inevitable that he should make many enemies, while he had the opportunity to make scarce any friends. He had nothing to conceal. He had often endeavoured to bring himself to a trial, but his adversaries had now done more for him than he was ever able to do for himself: they had brought him to the very fountam of justice and he willingly threw himself into it to be washed of all that was foul and superfluous. The manner of his trial and vindication he committed to the wisdom and justice of the House, asking only that instead of Sanchey's heaps of calumnies and reproach, he might receive a more distinct and particular charge, whereby he might be put in a way to vindicate himself effectually. Sanchey replied in a speech which, as reported by Petty, is remarkable for its violence and incoherence The House lost all patience with him and he was ordered to bring in his charges in writing. The next day, 22 April, Richard Cromwell dissolved Parliament and Petty was once more defrauded of his desired vindication.
Upon the dissolution of Parliament Petty hastened to Ireland, but soon returned to England again, being sent by Henry Cromwell to Fleetwood as one whom he could best trust now his nearest concernments were at stake . Sanchey, now a person of importance in the republican reaction, took advantage of Petty's presence in London to present to the Rump Parliament, 12 July, no less than eleven “new Articles of high misdemeanours, frauds, breach of trusts and several other crimes “chargeable against him. The Rump promptly referred them to the Commissioners for Ireland, before whom they never came to trial. The possibility of an official vindication being thus precluded, Petty resolved to carry his case before the bar of public opinion. With this end in view he published a succinct account of the dispute with Sanchey down to 13 July, 1659 , and the succeeding year he followed it up with a volume of nearly two hundred pages describing the work of survey and distribution, answering the charges brought against him, and explaining how they arose “from the envy and hatred of several parties promiscuously” and “from particular designing persons and parties” in Ireland. About October, 1659, he also prepared for the press, at great length, a History of the Down Survey containing what he regarded as a complete vindication of his conduct, and two further works, now probably lost, upon the same subject.
Among the clubs of the virtuosl to which, as Petty's will relates, it was his privilege to be admitted soon after he came to London, none is more memorable than that company of “capacious and searching spirits inquisitive into natural philosophy and other parts of human knowledge,” whose habit it was to meet for discussion either at Dr Goddard's lodgings in Wood Street or at the Bull's Head Tavern in Cheapside . There is no evidence that Petty was an original member of this company. But it appears probable that he was early invited to join their Invisible College , and it is certain that when parliamentary reorganization of the more visible colleges at Oxford brought Goddard, Wallis, Wilkins, and other followers of the new philosophy to the venerable home of the old, they there found in Petty an enthusiastic colleague. Their Oxford meetings were held first in his lodgings at the apothecary's because of the convenience of examining drugs and the like when there was an occasion, “and after his removal to Ireland (though not so constantly) at the lodgings of Dr Wilkins .” Those of the company who remained in London meanwhile continued their inquiries in a somewhat desultory manner until the Restoration brought back to the city the more prominent members of the Oxford branch, when it became necessary to change their place of meeting from the Bull's Head to the halls of Gresham College. Here the reunited company was in the habit of assembling for the discussion of questions in natural philosophy. They met regularly on Wednesdays and Thursdays, after the astronomy lectures of Christopher Wren and the geometry lectures of Lawrence Rooke , and on Wednesday, the 28th of November, 1660, after Wren's lecture, the conversation chancing to turn upon foreign institutions for promoting physico-mathematical experimental learning, the company then present, of whom Petty was one, resolved to improve this meeting to a more regular way of debating things and that they might do something answerable and according to the manner in other countryes for the promoting of experimental philosophy . Among those who, in pursuance of this plan, were invited to read papers before the association thus informally organized, Petty's name appears repeatedly , and when, with fitting circumstance, the association was incorporated (15 July, 1662) as the Royal Society for Improving of Natural Knowledge, he was named a charter member of its council.
Petty's famous plan for a “double bottomed” vessel, a sort of catamaran, which should excel in swiftness, weatherliness and stability any “single body” afloat, was probably set forth in one of his papers before the Society. To demonstrate the correctness of his views he built at least three such “sluice boats.” The first was laid down at Dublin in 1662. She distinguished herself by beating all the boats in the harbour, and subsequently outsailed the Holyhead packet, the swiftest vessel that the King had there. Hereupon Petty brought her to England , where, probably through the intervention of his friend Pepys, the attention of the Duke of York, then Lord High Admiral, and eventually the notice of the King himself was turned to the novel craft. Charles II. appears to have combined wonder at Petty's energy with quizzical amusement at his numerous projects. He at first chaffed the naviarchal Doctor without mercy , but relented sufficiently to attend the launching of a new Double Bottom which he dubbed “The Experiment .” She also proved herself a swift sailor, but was presently lost in the Irish Channel. This disaster, followed by the burning of several of his London houses in the great fire and by the adverse decisions of some of his Irish law suits , restrained Petty from further shipbuilding experiments for nearly a score of years; but in 1682, while he was considering the establishment at Dublin of a philosophical society similar to that of London, the fit of the Double Bottom, as he tells us, did return very fiercely upon him. His new vessel, however, performed as abominably, as if built on purpose to disappoint in the highest degree every particular that was expected of her and caused him to stagger in much that he had formerly said. But so much did he prefer truth before vanity and imposture that he resolved to spend his life in examining the greatest and noblest of all machines, a ship, and if he found just cause for it to write a book against himself .
The Restoration brought Petty no misfortune. A royal letter dated 2 Jan., 1660 , secured to him all lands that he had held on the 7th May, 1659, and the Acts of Settlement and of Explanation confirmed them to him by name. Like other owners of forfeited lands in Ireland, he suffered by the operation of the Court of Innocents in 1662, and was never able to convince himself that all who claimed innocency were in fact innocent . But in spite of his losses, he retained large Irish estates, and, in evidence of the King's approval, he was knighted and appears to have been appointed Surveyor-General of Ireland . The duties of this office at the time cannot have been more than nominal, for Petty continued to reside in London. During the Plague he withdrew to Durdens in Surrey where Evelyn found him, with Dr Wilkins and Mr Hooke, busied in contriving mechanical inventions .
In the spring of 1666 Petty was once more called to Ireland by the operations of the Court of Claims, and took up his residence in Dublin. During the ensuing period of his second prolonged stay in Ireland, he thoroughly identified himself with the material interests of that kingdom. As an army physician and surveyor of forfeitures, he had felt himself at most but a sojourner. As a Kerry landholder, able from Mount Mangerton in that country to behold 50,000 acres of his own land , he found abundant occupation, first in defending his titles during the sessions of the Court of Claims, and subsequently in managing his property. The uncertainity of titles in Ireland was great. “The Truth is,” said Essex, “ye Lands of Ireland have bin a meer scramble .” Flaws and defects of various sorts, based on allegations of illegal forfeiture, or of unpaid quit rents, were being continually found out, and it had become “A principal trade in Ireland to…prevail with persons conversant with the Higher Powers to give grants of these Discoveries, and thereupon, right or wrong, to vex the Prosecutors .” Petty by no means escaped such attacks. He refused to compromise, and in consequence his time was so fully occupied with defending himself that in 1667 he grimly entered “Lawsuits” as his only work accomplished .
Upon his escape from “the fire of this legal purgatory” Petty at once set about the improvement of what remained. His household was established at Dublin , but his most extensive possessions were at Kenmare in Kerry, and there he gradually built up an “industrial colony” of protestants. To this enterprise he gave the closest attention, making the difficult overland journey to that “obscure corner of the world twice a year through thick and thin .” The prospect was not encouraging. His Irish neighbours were hostile, and of Kenmare itself a well informed contemporary reported that while the harbours were very good for ships to load at, the place was so rocky and bare that it would hardly maintain people enough to keep a brogue-maker employed . But there were compensating advantages. The remote bay abounded with salmon. Abundance of wood made charcoal cheap and therefore he established iron and copper works, hoping vainly to discover Irish ores for their supply. The protestant colonists prospered in trade, as he had observed the heterodox everywhere to do , and Kenmare clearly demonstrated what thrift, backed by sufficient capital and directed by conspicuous shrewdness, could do for the real settlement of Ireland even under Charles II. After the accession of James II. the colonists fell victims to the jealousy of the surrounding Irish, whose violence was encouraged by Tyrconnel's policy, and thus the most successful of Petty's numerous experiments finally came to naught .
As Petty's stake in the prosperity of Ireland grew larger, his interest in the affairs of the kingdom likewise increased. He had been a member of the Irish parliament of the Restoration , and one of the commissioners appointed to execute the Act of Settlement, he had taken a prominent part in opposing the bill which prohibited the importation of Irish cattle into England , and he had even attempted, though apparently quite ignorant of the law, to fill the position of a judge of admiralty; but the incidental discharge of these public duties had little or no effect upon the subsequent course of his life. His concern with the public revenues of Ireland was far more significant. As early as 1662 he had “frequently applied to present state and affairs of Ireland” certain of the conclusions reached in his “Treatise of Taxes.” To the mere theoretical interest in the subject thus evinced, the events of later years added an interest of a very practical character. In 1668 charges of mismanagement of the Irish revenues were brought against Ormond, the Lord Lieutenant, and Anglesey, the Lord Treasurer , by certain persons who desired to farm the revenues themselves. Their intrigue was successful, and the King agreed with them for seven years from Christmas, 1668, for £219,500 per annum . The management of the new farm was both unsatisfactory to the exchequer and oppressive to the subject . Especially did the energy of the farmers in collecting alleged arrears of quit-rents stir the landowners thus charged to active resistance. Among them was Petty. He promptly took up a “legal fight with the farmers,” an account of which occupies for several years a large space in his correspondence with Southwell. His tone makes it evident that a considerable spice of personal animosity was thus added to his previous disgust with the inequalities of Irish taxation and in part explains his subsequent conduct. As the time drew near for the farm of 1668 to expire, he resolved to carry the war into the enemy's camp. Accordingly in the latter part of 1673 he made his way to London and became a bidder, on what he considered a reformed basis, for the new farm beginning Christmas Day, 1675. It appears that an agreement with him was actually made but Ranelagh's influence with Buckingham was sufficient to procure its abrogation and the substitution of the scandalous contract under which Ranelagh, Lord Kingston, and Sir James Shaen continued to mismanage the finances of Ireland until Ormond finally exposed them . Meanwhile Petty remained more than two years in London, renewing his old acquaintances and becoming once more a member of the Council of the Royal Society .
In the summer of 1676 Petty once more took up his residence in Ireland, where, save for visits to London in the spring of 1680, he remained almost five years . It was during this period that he wrote the “Political Anatomy of Ireland,” the “Political Arithmetick,” and the “Observations on the Dublin Bills .” He also fell into a new quarrel with the farmers, the result of which for a time overclouded even his invincible cheerfulness. His chief adversary, Ranelagh, being Chancellor of the Exchequer as well as farmer of the taxes, was able to procure his imprisonment for contempt of court. Thus vexed by the wicked works of man, he refreshed himself by pondering the wonderful works of God. The result was a Latin metrical translation of the 104th psalm, copies of which he sent with long complaints to Southwell and to Pepys. But his native whimsically soon reasserted itself. “Lord,” he exclaims, “that a man fifty-four years old should, after thirty-six years discontinuance, return to the making of verses which boys of fifteen years old can correct: and then trouble Clerks of the Council and Secretaries of the Admiralty with them. “
The reappointment of Ormond in 1677 to the Lord Lieutenancy of Ireland, in the room of Essex, whose opinon of Petty was not high brought about a lull in his dispute with the farmers, and after his recovery from the illness which had alarmed him in November of that year, there remained nothing to mar his pleasure in the prosperity of his affairs. He even began to think seriously of the possibility of exercising greater influence in public matters. About the time of his marriage he had been approached concerning a peerage. The condition then suggested was the payment of such a sum as, in view of his recent losses, Petty did not care to spend “in the market of ambition,” and he thanked the royal emissary with scant courtesy. In 1679, when Temple was planning to remodel the Irish Privy Council upon the same lines that he had followed in England and the protestant party at court had marked Petty for appointment to the reconstituted body, the offer of a peerage was again made to him. He seems in the mean time to have changed his opinion of “people who make use of titles and tools” and accordingly he made a journey to London, apparently with the intention of securing both the title and the seat at the Council table. But Charles II. answered the protestants that by their good leave he would chose his own council for Ireland, and Petty fearing that “a bare title without some trust might seem to the world a body without soul or spirit ,” declined the peerage for a second time. Perhaps he consoled himself, as on the previous occasion, by reflecting that he “had rather be a copper farthing of intrinsic value than a brass half-crown, how gaudily soever it be stamped and guilded.”
Upon his return to Ireland, 22 March, 1680, his old controversy with the farmers broke out again, and the vigour of his attack upon their abuses attracted such attention that he was summoned to London in June, 1682, to take part in the discussion then going on before the Privy Council, as to the reorganization of the Irish revenues. He proposed the abolition of the farm, which was finally accomplished, and the imposition of a heavy ale license. Apparently he was not adverse to undertaking the direct collection of the taxes himself, but “by good luck” he “never solicited anybody in the case.” His old rival, Sir James Shaen, now offered to increase the King's revenue nearly £80,000 a year upon a new farm—” a farm indeed, as it was drawn up” says Temple, “not of the revenue but of the crown of Ireland “But the powerful influence of Essex, whom Temple charges with intriguing for a reappoinment to the Lord Lieutenancy, was thrown in Shaen's favour, Petty was represented by some to be a conjurer and by some to be notional and fanciful near up to madness the needs of the Exchequer were urgent, and the plan that promised ready cash was adopted. Deeply disappointed, Petty returned to Ireland in the summer of 1683 and solaced himself with a journey into Kerry, and presently with a renewal of the experiments that had occupied his mind some twenty years before . He built a new double bottom and was active in the establishment of the Dublin Philosophical Society , for which he wrote several papers.
News of the accession of James II caused Petty to return to London in the early summer of 1685. The new occupant of the royal office had been not less gracious to him than was his predecessor, and Petty fancied the time now ripe to secure for Ireland the adminstrative reforms on which his heart was set. His plans for the revision of the farm and for the establishment, under his own supervision, of an Irish statistical office seemed for a time to be going well, and he attributed undue importance to the interviews which the King granted him upon this and other Irish matters. It was not until later that he appreciated the extent to which, under the new regime, his own personal interests were being drawn to his disadvantage into the larger currents of public affairs. Among the policies which, from time to time, were indistinctly indicated by the vacillations of James II., that looking towards independence of Louis XIV. and the resumption by England of a leading place in the affairs of Europe appealed to Petty with peculiar force. Ten years before, in the “Political Arithmetick,” he had argued England's material fitness for such a place, and had proved, to his own satisfaction at least, that in wealth and strength she was potentially, if not actually, as considerable as France. He now reverted to the same theme, writing a series of essays, in order, by the methods of his political arithmetick, to demonstrate to the satisfaction of the King that London was the greatest city in the world. These efforts excited some attention among the curious, both at home and abroad , but they produced no traceable effect upon the policy of James II.
Petty appears to have realized that independence of France demanded harmony at home, and to have welcomed James's Declarations of Indulgence as wise measures for the unification of national sentiment. Knowing as he did the immense material preponderance of the protestant interest both in England and especially in Ireland —a preponderance of which he did his best to convince the King by written and by oral argument —he was unable to believe that the Declarations, whose sentiments quite accorded with his own views were really issued in the sole interest of the Roman Catholics, and he continued to regard the boastings of Tyrconnel and the extreme Irish faction as without foundation in the intentions of the king . But at length tidings of the alarm prevalent among the English protestants in Ireland, and especially the news that McCarthy had been appointed governor of the province of Kerry, brought home to him the danger with which he himself, as well as the other protestants in Ireland, were threatened.
It is not certain whether Petty lived to know that Kenmare was destroyed. For some months he had been unwell. In spite of a “great lameness” he attended the annual dinner of the Royal Society on St Andrew's day. He went home ill. His foot gangrened and on December 16 he died at his house in Piccadilly.
On Trinity Sunday, June 2, 1667, Petty had married Elizabeth, daughter of his old friend Sir Hardress Waller, and widow of Sir Maurice Fenton. Though Lady Petty, “a very beautifull and ingeniose lady, browne, with glorious eies ,” was much younger than her husband and of a taste as magnificent as his was simple , their married life was most happy. Nowhere does Petty appear to greater advantage than in his letters to his wife, and her letters to him fully bear out Evelyn's judgment, “she was an extraordinary wit as well as beauty and a prudent woman.”
Three of Petty's contemporaries, men of different temperaments and attainments, have put on record their impressions of him. John Aubrey says that he was a proper handsome man, measured six-foot high, with a good head of brown hair moderately turning up. His eyes were a kind of goose-grey, very short sighted and as to aspect beautiful; they promised sweetness of nature and they did not deceive, for he was a marvellous good natured person. His eye-brows were thick, dark and straight, his head very large. Evelyn declared him so exceeding nice in sifting and examining all possible contingencies that he ventured at nothing which is not demonstration. There was not in the whole world his equal for a superintendent of manufactures and improvement of trade, or to govern a plantation. “If I were a prince, I should make him my second counsellor at least. There is nothing difficult to him… Sir William was, with all this, facetious and of easy conversation, friendly and courteous, and had such a faculty of imitating others that he would take a text and preach, now like a grave orthodox divine, then falling into the Presbyterian way, then to the fanatical, the Quaker, the monk and friar, the Popish priest, with such admirable action and alteration of voice and tone, as it was not possible to abstain from wonder, and one would swear to hear several persons, or forbear to think he was not in good earnest an enthusiast and almost beside himself; then, he would fall out of it into a serious discourse; but it was very rarely he would be prevailed on to oblige the company with this faculty, and that only amongst most intimate friends. My Lord Duke of Ormond once obtained it of him, and was almost ravished with admiration; but bye and bye, he fell upon a serious reprimand of the faults and miscarriages of some Princes and Governors, which, though he named none, did so sensibly touch the Duke, who was then Lieutenant of Ireland, that he began to be very uneasy, and wished the spirit laid which he had raised, for he was neither able to endure such truths, nor could he but be delighted. At last, he melted his discourse to a ridiculous subject, and came down from the joint stool on which he had stood; but my lord would not have him preach any more. He never could get favour at Court, because he outwitted all the projectors who came near him. Having never known such another genius, I cannot but mention these particulars, among a multitude of others that I could produce.” And Pepys, who had heard everybody, found Petty “the most rational man that ever he heard speak with a tongue.”
PETTY'S ECONOMIC WRITINGS.
Those who hitherto have discussed Petty as a writer on economic subjects have confined themselves pretty closely to summary and criticism of his theories. The writings are now before the reader, who may summarize and criticize as his purpose demands or his taste suggests. It remains for the editor to account, if he can, for the writings as they are.
A man of force makes his way in this world through no impalpable ether. The medium through which he moves is dense, and deflects his course now this way, now that, according to the form and temper of the surface that he presents to the buffeting of affairs. His intellectual orbit cannot be precisely calculated even with a knowledge of the initial direction and velocity of his mind and of the attraction which draws its flight towards a fixed centre. But every man not wholly erratic is at once impelled by his circumstances and restrained by his training. Postulate these, and you may discover in his actual course some trace of the mean orbit which calculation would predict.
The inspiration of Petty's writings is not far to seek. Written before the days of formal treatises on political economy, they are neither the systematized abstractions of a metaphysician condescending to every-day affairs, nor the less systematic but no less abstract arguments of a man of affairs with an undisciplined bent toward speculative thinking. Least of all are they the eclectic treatise of a professional economist laborously dovetailing the ideas of his predecessors one into another. Indeed it is doubtful whether Petty had any acquaintance worth mentioning with such economic writings as existed in his day. In his earlier years, to be sure, he had been a man of the library as well as of the laboratory; but experience taught him to value the education of life above that of books, and in his writings he uses authorities seldom and not well. To Aubrey he declared that he had read little since his twenty-fifth year, and was of Hobbes's mind, that had he read much, as some men have, he had not known as much as he did . His writings then are not conscious elaborations of some economic system, more or less clearly conceived. Each of them, on the contrary, was prompted by some circumstance of the times, and addresses itself, in fact if not in form, to some question of the day. The “Treatise of Taxes” the most systematic of them all, grows out of the changes in the revenue which the Restoration occasioned. The “Verbum Sapienti” is due to the costliness of the first Dutch war, the “Quantulumcunque” is the recomage projects of Halifax. The moral of the “Political Arithmetick,” implicit but clearly implied, is that Charles II. may, if he will, make himself independent of the bribes of Louis XIV. “The doctrines of this essay offended France .” The “Essays in Political Arithmetick” instruct James, wavering on the verge of an independent policy, that London is more considerable than the two best cities of the French monarchy . The unedited “Treatise of Ireland” plainly avows its political purpose. Even the “Political Anatomy” though suggested by Chamberlayne's enclyclopaedic “State of England “is seen, upon briefest examination, to be crowded with such discussions of current questions as nowhere occur in its prototype. Nevertheless they are all marked, in part because of his method of investigation, by certain common and characteristic features.
The form of Petty's discussions is as directly traceable to his training as is the contents of them to his circumstances. Such a title as “Political Anatomy” is reminiscent of his early studies, but the education which vitally affected his writing was rather that of converse with his scientific friends than that afforded by the instruction of his formal teachers. I shall try, therefore, to account in part for Petty's economic writing by taking up first the intellectual influences which gave them their characteristic form, and afterwards the circumstances, within the limits prescribed by that form, which suggested their content.
Petty has been represented, not without reason, as the disciple of Hobbes . We have seen that he studied with Hobbes at Paris, and we know that all through Hobbes's quarrels their friendship remained unbroken . Petty's high opinion of the author of the treatise “De Cive” is indicated by the inclusion of that work in the list of books which he wished his sons to read,—and the list is not a long one . In his economic writings too there are traces of Hobbes's influence, but it is—if the distinction be admissible—upon Petty as a politician rather than upon Petty as an economist that his influence was chiefly exerted. It appears most strikingly in the assumption that the government is justified in doing anything by which the national wealth can be increased. Again and again Petty advocates sweeping public measures which take no account whatever of the rights and sensibilities of the citizen. He is quite ready to suggest that the majority of the Irish and Scotch be transplanted to England whether they consent or not . In this general sense he is certainly of the political school of Hobbes rather than of Harrington .
The attempt to trace Hobbes's influence in Petty's attitude towards the relation of church and state does not seem altogether successful. In harmony with his general views, Petty agrees with Hobbes that the state may suppress dissent. Beyond this initial proposition they part company. The political theory of “The Leviathan” tolerates no division of sovereignty. Dissenters from the church by law established are political offenders who must be reduced to conformity because their dissent impairs the sovereignty of the government. Petty's reason why dissent may be suppressed is quite different from this. He thinks that “the Magistrate may punish false Believers, if he believes he shall offend God in forbearing it,…for the same reasons that men give for Liberty of Conscience and universal tolleration .” In other words a man vested with magisterial powers is morally justified in using them as his conscience dictates. But Petty himself is far from thinking it either necessary or expedient to use such powers to secure uniformity of worship. On the contrary he warmly commends the heterodox, though with curious reservations lest by going too far he give offence , and he regards dissent as not only harmless but inevitable. Thus upon a calculation of the number of sermons annually preached in England, he remarks that “It were a Miracle, if a Million of Sermons Composed by so many Men, and of so many Minds and Methods, should produce Uniformity upon the discomposed understandings of about 8 Millions of Hearers ,” and suggests that misbelievers, provided they keep the public peace , may wisely be indulged by the magistrate, upon payment of “well proportioned, tolerable pecuniary mulcts, such as every conscientious Nonconformist would gladly pay, and Hypocrites by refusing, discover themselves to be such .” For “no man can believe what himself pleases and to force men to say they believe what they do not, is vain, absurd, and without honour to God.” Besides “where most indeavours have been used to help Uniformity, there Heterodoxy hath most abounded .” The best policy therefore is for the government to pluck with moderation the geese who persist in their unauthorized beliefs .
Upon Petty as an economist the influence of Hobbes was far outweighed by that of Bacon. There was of course no personal connection here. When the founder of the New Philosophy was dying at Highgate, the future political arithmetician was a weaver's brat in Hampshire. But the youth became, as he grew to manhood, an eager member of that group of experimental investigators, working in the spirit of the “Novum Organum,” who began the systematic pursuit of scientific knowledge in England . At the close of a century distinguished above its predecessors not so much by the spirit of research as by the passion for accuracy in the determination of results, it is easy to find food for indulgent merriment in their crude apparatus. Not less amusing are their experiments with “a toad set in the middle of a circle of powder made with unicorne's horne,” whose supposed charm it refused to recognize, incontinently hopping out of the circle again and again; or Sir Kenelm Digby's recommendation of “calcined powder of todes reverbrated applyed in bagges upon the stomach of a pestiferate body”—a pungent treatment of pestiferous bodies, whose obsolescence with the gradual mollification of social usages some will be found to regret. But the mere willingness to put the conduct of the toad to the test and to abide by the result argues confidence in the usefulness of experiment, and by implication in the uniformity of nature. It points the way to that precise knowledge of the world which alone can afford a firm foundation for invention and thus lead to the rule of man. It exhibits the Baconian rather than the Spinozistic sense of the maxim Knowledge is Power. It explains why the “Novum Organum” treats “De interpretatione naturæ sive de regno hominis.” With the spirit of this philosophy Petty was strongly imbued . In a session of the Royal Society when some one chanced to use the words “considerably bigger,” “Sir William Petty cautioned, that no word might be used but what marks either number, weight, or measure .” The caution may serve to indicate the nature of Bacon's influence over him. It was an influence exerted primarily upon Petty's method, and only indirectly, through his method, upon the substance of his economic speculations.
In the field of his peculiar interests Petty sought the same quantitative precision which he demanded of his scientific colleagues. Now in economic investigation, as writers on the method of political economy never weary of iterating, the experimental method is in general precluded by the nature of the materials. The far seeing minister of an autocratic Czar may sometimes make industrial experiments on a gigantic scale and even isolate them from the disturbing influences of parliaments and newspapers, but he is not at all likely to utilize them for purposes of economic speculation. A favoured economist like Von Thunen—with whose aims Petty's thought exhibits much affinity though he lacks Von Thünen's conspicuous patience—may make similar experiments upon a small scale. Most of us, however, must get on as best we may without any economic laboratory whatever. In this respect Petty was no exception. Experiment being impossible, he substituted what he called Political Arithmetick, a beginning of what is now called statistics. It was by no happy chance that he turned to this new device. He had a perfectly clear conception of the end which he desired to reach and of the means by which he proposed to reach it. “The Method I take,” he says, “is not yet very usual; for instead of using only comparative and superlative Words, and intellectual Arguments, I have taken the course (as a Specimen of the Political Arithmetick I have longed aimed at) to express my self in terms of Number, Weight, or Measure; to use only Arguments of Sense, and to consider only such Causes, as have visible Foundations in Nature; leaving those that depend upon the mutable Minds, Opinions, Appetites, and Passions of particular Men, to the Consideration of others: Really professing my self as unable to speak satisfactorily upon those Grounds (if they may be call'd Grounds), as to foretel the cast of a Dye; to play well at Tennis, Billiards or Bowles, (without long practice,) by virtue of the most elaborate Conceptions that ever have been written De Projectilibus & Missilibus, or of the Angles of Incidence and Reflection .”
He even anticipated the modern conclusion that statistical investigation, applied to wisely selected circumstances, affords perhaps the best substitute for experimentation that is open to an economist. In this sense he says, in the preface to the “Political Anatomy of Ireland,” “As Students in Medicine, practice their inquiries upon cheap and common Animals, and such whose actions they are best acquainted with, and where there is the least confusion and perplexure of Parts; I have chosen Ireland as such a Political Animal, who is scarce Twenty years old; where the Intrigue of State is not very complicate, and with which I have been conversant from an Embrion; and in which, if I have done amiss, the fault may be easily mended by another .” The obvious meaning is, not that he literally experimented upon Ireland himself, but that he examined by the best available means, the effects of such experiments as had been made there. The means turns out to be the use of political arithmetick, and that he considers the best means because it gives precise results. As we shall see, Petty's results were, at times, less accurate than precise, for his statistical materials were frequently inadequate and his employment of such as he had was sometimes injudicious. But the root of the matter was in him. The application of an appropriate method “not yet very usual” to a field of knowledge in which it was altogether new, justifies him in associating himself with the most eminent followers of the new philosophy, and even distinguishes him among his colleagues. It was by no misapprehension of his true significance that Narcissus Luttrell wrote in his diary simply, “Sir William Petty of the Royal Society is dead .”
The data of statistics do not now, nor did they ever present themselves spontaneously for scientific elaboration. In order therefore that legal provision should be made, and that money should be forthcoming, for their ascertainment, it was first necessary that the value of possible statistical deductions from accurate data should be demonstrated by the intelligent use of those sparse materials which lay ready to the student's hand. It is in this sense that we must judge the essays of Graunt and Petty, which pioneered the way of modern statistics, and so judged they will be found worthy of high praise. Graunt's book has the advantage of priority and the greater advantage of dealing with a body of statistical data sufficiently extended and complete to warrant some confidence in deductions properly made from it. Petty's materials, on the other hand, were highly defective. A few scattering bills from Paris and Dublin, haphazard returns from various tax offices, a guess here or there as to the area of a city —the list is soon exhausted. Petty realized the incompleteness of his data, and repeatedly urged the institution of regular statistical returns . He drew up a pattern for an improved bill of mortality for Dublin . He even tried to secure the establishment of an Irish statistical office under his own management . But it is not clear that anything of importance resulted from his efforts in this direction. Meanwhile he made shift with such tools as came to hand—”a commin Knife and a Clout,” as he says “instead of the many more helps which such a Work requires .” When he could not ascertain directly the number, weight or measure of some phenomenon in which he was interested, he reckoned out what he desired to know upon the basis of what he already knew. In other words he pursued the method of political arithmetic as distinguished from statistics. Statistics demands enumeration. The validity of its inferences depends upon the theory of probabilities as expressed in the Law of Large Numbers. Therefore it adds, it does not multiply. Political arithmetic, as exemplified by Petty, multiplies freely; and the value of its results varies according to the nature of the terms multiplied. For example, in the absence of a census Petty had to calculate the population of London, of England, and of Ireland. His calculations for London are based upon the number of burials and upon the number of houses, facts which at least bear some relation to the number of people. The burials he multiplies by thirty, an arbitrary figure for which he pleads Graunt's authority ; the houses he multiplies, now by six , and now by eight , as suits his purpose. The sources of probable error are obvious. The population of England, he further estimates at eleven times that of London because London pays one eleventh of the assessment. The chance of error is thus raised to the second degree. Nevertheless the calculation is not altogether unreasonable, and Petty asserts that the results “do pretty well agree” with the accounts of the hearth money, the poll money, and the bishops’ numbering of the communicants —figures which he neglects to give. To see from what refractory materials he can extract a result when hard pushed, we must turn to his discussion of the Irish rebellion of 1641. He finds that above one-third more “superfluous oxen and sheep, butter and beef” was exported from that kingdom in 1664 than before the rebellion, “which shows there were ⅓ more people in 1641 than in 1664 .” Unfortunately the use of rash calculations grew upon Petty, and, as was to be expected, he gives widely varying estimates of the same things . It must be added that he is frequently inaccurate in his use of authorities and careless in his calculations and upon at least one occasion he is open to suspicion of sophisticating his figures .
Petty's economic writings thus exhibit both the strength and the weakness of his characteristic method. When his terms of number, weight and measure result from an actual enumeration they are generally of value, for he has a considerable capacity of segregating the really significant factors of an economic problem. But the difficulties in the way of enumeration were great, and in his eagerness for results he often resorted to calculations which were nothing more than guesses. When he stopped to think, he was well enough aware of their conjectural character. “I hope,” he writes to Aubrey, “that no man takes what I say about the living and dyeing of men for a mathematical demonstration .” But in the ardour of argument he was himself more than once mislead into fancying that his conclusions were accurate because their form was definite. His mistake is not without its modern analogies. Mathematical presentations of industrial facts, both symbolic and graphic, have by their definiteness, encouraged many an investigator in the false conceit that he now knew what he sought, whereas he had at most but a neat name for what he sought to know. Nevertheless the substitution of symbols for Petty's “terms of number” is an improvement in this, that calculations made in symbols must be consciously translated into the terms of actual life before any practical use—or misuse—can be made of them, whereas calculations in figures of number, weight and measure are already concrete and appear to tell something intelligible even to a common man. Had Petty calculated the advantages of his “perpetual settlement of Ireland with a natural improvement of England and Ireland by transplanting a million of people out of Ireland into England” in the form of curves and triangles, that astounding proposition might have passed for something highly scientific.
It would be quite possible to take up the various economic topics discussed by Petty according to modern conceptions of them, and to do so would afford a ready-made standard for judging his economic notions. But it would also involve the risk of asking what he thought about problems concerning which it never occurred to him to think at all. No possible answer to such a question can be correct, for the question itself is irrational. Accordingly I leave to those who have a taste for mosaic work and are not yet satisfied with the amount on hand, the task of determining in what details Petty anticipated Smith or Ricardo or Bòhm-Bawerk. It will be enough for the present purpose to indicate a few of the chief economic questions which engaged his attention and to attempt to understand why he attacked them and how he solved them.
The economic method which Petty chiefly pursued, taken in combination with the limited extent of his materials, of necessity confined him to the discussion of a few out of the many questions that must have thronged upon his active mind. In no other field of economic interst were so many figures available as in that of taxation, and the fiscal changes of the Restoration, chancing to come just at the time when he first had leisure to return to his studies, gave to his economic inquiries a direction from which he never wholly departed. The only topic neither an outgrowth of his fiscal discussions nor otherwise dictated by his arithmetical method upon which he wrote at length was that of coinage. And it is noteworthy that his little excursions into this relatively foreign field are marked by as great perspicuity and good sense as distinguish his more arithmetical writings. The “Quantulumcunque,” indeed, shows Petty very nearly at his best.
As an economic writer then, Petty is essentially a cameralist rather than a mercantilist. Unlike Robinson and Mun and Child, he had little connection with foreign trade ; nevertheless he was too much infected by prevalent mercantile views to see the advantages of unrestricted commerce as clearly as North was able to do. Accordingly while he leans, on the whole, towards a policy of commercial freedom, and is quite clear and consistent in opposing all restraints upon the export of coin or bullion, he seems at times to evade the discussion of the free trade problem—e.g. he does not mention the Act of Navigation—and his utterances on the preferability of treasure to other forms of wealth, on the balance of trade, and on the policy of restriction generally are contradictory, not to say vacillating. On almost all questions of public revenue and public expenditure, on the contrary, his opinions are well developed, clear and consistent. The great changes in the fiscal system which were made by the Convention Parliament gave rise to no other discussion at all comparable with his “Treatise of Taxes and Contributions ;” and it is scarcely too much to say that English economic literature before Hume can show no tract of such range and force, characterized by such wealth of suggestion and such power of analysis, as is Petty's masterpiece. It contains the germ of nearly every theory which he afterwards elaborated. Even his method of political arithmetic is exemplified in the calculations of its second chapter . The calculations are, to be sure, both slight and unsatisfactory; but rather from lack of trustworthy data than from any failure on Petty's part to appreciate the importance of such devices. On the contrary he demands for economic purposes a thorough survey of lands and their produce , and of money, wages and population, for “until this be done trade will be too conjectural a work for any man to employ his thoughts about “Before the publication of the “Treatise” he was indeed acquainted with Graunt's “Observations ,” but the suggestions of that book had not had as yet sufficient time to exert their full influence upon him. Consequently the number of the people, which becomes in the “Verbum Sapienti” (1664) a key to the national wealth, and thus affords a basis for the distribution of taxation much more satisfactory than expenditure , is used in the “Treatise” but incidentally to a minor question of retrenchment .
To the problem of national wealth Petty never tires of applying the methods of his political arithmetic. The “Verbum Sapienti” shows both the reason that led him to attack the problem and the method which he employed for its solution. The introduction explains that taxation is unequal, “which disproportion is the true and proper grievance of taxes “To the end that the public charge be laid proportionally it is necessary that the total effects of the nation be ascertained. In the first chapter, accordingly, Petty estimates separately the value of the lands, the houses, the shipping, the cattle, the money and the miscellaneous goods of the country, unblushingly confirming one guess by showing its satisfying conformity to another. Now-a-days more abundant and more accurate figures are available upon which to base guesses, but the methods of modern calculations of national wealth are, so far, not essentially different from his . The second chapter, however, adds to the calculation of the first an element of national wealth which seldom figures in modern tables headed £ s. d. This element is “the value of the people,” which it was his consistent practice to include in all his estimates. Fewness of people he thought was real poverty . Hands were the father as lands were the mother of wealth , and neither of the pair might be omitted from a stock-taking of the public household. The suggestion that people are wealth was probably much older than Petty , and his originality would consist rather in the application to it of his political arithmetic than in the invention of the notion. Now in order to add hands to lands he must reduce them to a common denominator. The necessity and the difficulty of thus making “a par and equation between lands and labour” must have been brought home to him by his experience as surveyor and commissioner of allotments, charged with rewarding soldiers on the one hand and loaners of money on the other by proper assignment of the forfeited lands in Ireland , and it is not merely for theoretical purposes that he regards this task as “the most important consideration in political oeconomies .” The common denominator chosen being money, it is necessary to determine the money value of the people. But the people in question are neither bought nor sold , and so he resorts to a calculation. Assuming the expenditure of the people of England to be forty million pounds per annum, he finds that their income from property is sufficient to meet only fifteen millions of it. The source of the remaining twenty-five millions of income is worth as much as the fee of land that would rent for that sum, “for although the individiums of mankind be reckoned at about eight years purchase, the species of them is worth as many as land, being in its nature as perpetual for ought we know .” The figures to which Petty applies this formula are conjectural, even capricious, but the formula itself is essentially sound, and the ingenious calculation shows that he had a firm grasp upon the problem of capitalization. The various components of the national wealth being thus ascertained, Petty proceeds to use them as a basis for distributing taxation. He holds that, the ratio formalis of riches lying rather in proportion than in quantity, men would be no poorer than now they are should each lose half his estate . Accordingly he proposes various taxes intended to place upon the possessors of each source of income such a proportion of the aggregate burden as the capitalized amounts of their respective incomes may bear to the national wealth which he has calculated.
Petty's interest in the amount of the national wealth thus sprang from his discussion of taxation, and it is clear that traces of its origin hang about it to the end. But he soon came to employ the notion for another purpose also; that is, as a means of comparing England with her commercial rivals, Holland and France. In 1664, Petty had made a “Collection of the Frugalities of Holland ,” and he repeatedly commended various Dutch practices for adoption in England . Nevertheless, he seems to have considered the current estimate of the Dutch somewhat exaggerated , and the conviction apparently grew upon him that it was rather with France than Holland that Englishmen must reckon . In the “Treatise of Taxes” (1662), the Dutch system is held up as a model for English imitation, while no French taxes are mentioned except the gabelle , of which he disapproves. In the “Political Arithmetick” (1676) Holland still occupies the first place, but it serves merely as a stalking-horse to disguise the main argument regarding the potential superiority of England to France. In the “Five Essays” (1687) the Netherlands are openly relegated to second place. In making these international comparisons Petty realizes that national wealth is something different from the revenue of the exchequer , and is of independent importance to the commonweal. Nevertheless he is unable to divest himself entirely of the cameralistic notions out of which his discussion arose, and always lays especial weight upon the distinctively fiscal importance of lands and goods and people.
Income being with Petty the starting point for estimating wealth, he feels the necessity of explaining those sorts of income–rent and interest–which do not result evidently from current labour. Now the fundamental question arising alike in a theory of rent and in a theory of interest is this: why does the right to receive a definite annual payment throughout an infinite succession of years command in the market only a finite sum? As applied to rent, this is the question of the number of “years purchase,” and Petty, who frequently employs that common phrase, also discusses the problem. But this was aside from his main purpose, and he neither dwelt on the suggestion nor applied it to money. He recognized that the value of the fee depended upon the rent which the land would yield, and was therefore interested rather in ascertaining as a factor in his studies of national wealth and its growth, why a specific piece of land bears a certain rent and neither more nor less, than in determining the capital value of that rent. The answer is given in a remarkable passage in the “Treatise of Taxes,” and is elaborated in the “Political Anatomy of Ireland.” The corn rent of agricultural lands, he says, is determined by the excess of their produce over the expenses of their cultivation, paid in corn, and the money value of this excess will be measured by the amount of silver which a miner, working for the same time as the cultivator of the corn land, will have left, after meeting his expenses with a part of the silver which he secures. The labour theory of value thus adopted was probably suggested by Hobbes. But to the question why there should be any surplus of value above costs either in cornfarming or mining he has an answer of his own. This answer differs from that now become familiar. The notion of diminishing returns, forcing recourse to fields of inferior natural and indestructible powers in order to supply the market and thus giving rise to a differential rent, did not occur to him. On the contrary he probably thought that with proper cultivation, the profitable fertility of land could be indefinitely increased . But he suggested in the “Treatise ,” and asserted in the “Political Arithmetick “that the amount of rent per acre is determined by the density of the population dependent for food upon the land, and varies inversely as the said density. In other words the rent of land is attributed to its situation rather than to its technical fertility. The formula has a similar arithmetical neatness to that of the formula commonly called Ricardian, and it comes, on the whole, perhaps quite as near to measuring the commercial facts . This praise, if praise it be, is not deemed unduly high.
In interest Petty recognizes two elements, a compensation for risk , and a payment for the inconvenience which a man admits against himself in giving out his money so that he may not demand it back until a certain time, whatever his own necessities shall be in the mean time . The amount of this last payment, upon any specific sum–in modern language the rate of interest per cent.—cannot be less than the rent of so much land as that sum would buy . Exchange he explains as “local usury” meaning, apparently, a compensation for the costs of moving money, of which costs risk is the largest.
A theory of wages was not demanded by Petty's method of calculating national wealth. For that purpose he could take them as a given fact, or rather as a fact inferable from the labourer's expenditures, and as he had no conception of the problem of distribution in the modern sense and was interested rather in the aggregate number of labourers than in their individual differences, he contents himself with a passing suggestion that wages generally are the result of, and equal to, the increase which a man can effect by his labour in the spontaneous productivity of the soil . The only other distributive suggestion regarding wages is the remark, wholly incidental, that when wages of husbandmen rise rents of land must consequently fall .