Essays on Mankind and Political Arithmetic

by Sir William Petty

Petty’s Maps were printed in 1685, two years before his death, as “Hiberniæ Delineatio quoad hactenus licuit perfectissima;” a collection of thirty-six maps, with a portrait of Sir William Petty, a work answering to its description as the most perfect delineation of Ireland that had up to that time been obtained. There is a coloured copy of Petty’s maps in the British Museum, and also an uncoloured copy, with the first five maps varying from those in the coloured copy, and giving a General Map of Ireland, followed by Maps of Leinster, Munster, Ulster, and Connaught. There was afterwards published in duodecimo, without date, “A Geographical Description of ye Kingdom of Ireland, collected from ye actual Survey made by Sir William Petty, corrected and amended, engraven and published by Fra. Lamb.” This volume gives as its contents, “one general mapp, four provincial mapps, and thirty-two county mapps; to which is added a mapp of Great Brittaine and Ireland, together with an Index of the whole.”

At the Restoration William Petty accepted the inevitable change, and continued his service to the country. He was knighted by Charles the Second, and appointed in 1661 Inspector-General of Ireland. He entered Parliament. He was one of the first founders of the Royal Society, established at the beginning of the reign of Charles the Second; and the outcome of these scientific studies along the line marked out by Francis Bacon, which had been actively pursued in Oxford and at Gresham College. In 1663 he applied his ingenuity to the invention of a swift double-bottomed ship, that made one or two passages between England and Ireland, but was then lost in a storm.

In 1670 Sir William Petty established on his lands at Kerry the English settlement at the head of the bay of Kenmare. The building of forty-two houses for the English settlers first laid the foundations of the present town of Kenmare. “The population,” writes Lord Macaulay, “amounted to a hundred and eighty. The land round the town was well cultivated. The cattle were numerous. Two small barks were employed in fishing and trading along the coast. The supply of herrings, pilchards, mackerel, and salmon, was plentiful, and would have been still more plentiful had not the beach been, in the finest part of the year, covered by multitudes of seals, which preyed on the fish of the bay. Yet the seal was not an unwelcome visitor: his fur was valuable; and his oil supplied light through the long nights of winter. An attempt was made with great success to set up ironworks. It was not yet the practice to employ coal for the purpose of smelting; and the manufacturers of Kent and Sussex had much difficulty in procuring timber at a reasonable price. The neighbourhood of Kenmare was then richly wooded; and Petty found it a gainful speculation to send ore thither.” He looked also for profit from the variegated marbles of adjacent islands. Distant two days’ journey over the mountains from the nearest English, Petty’s English settlement of Kenmare withstood all surrounding dangers, and in 1688, a year after its founder’s death, defended itself successfully against a fierce and general attack.

Sir William Petty died at London, on the 16th of December, 1687, and was buried in his native town of Romsey. He had added to his great wealth by marriage, and was the founder of the family in which another Sir William Petty became Earl of Shelburne and first Marquis of Lansdowne. The son of that first Marquis was Henry third Marquis of Lansdowne, who took a conspicuous part in our political history during the present century.

Sir William Petty’s survey of the land in Ireland, called the Down Survey, because its details were set down in maps, remains the legal record of the title on which half the land in Ireland is held. The original maps are preserved in the Public Record Office at Dublin, and many of Petty’s MSS. are in the Bodleian Library at Oxford.

He published in 1662 and 1685 a “Treatise of Taxes and Contributions, the same being frequently to the present state and affairs of Ireland,” of which his view started from the general opinion that men should contribute to the public charge according to their interest in the public peace—that is, according to their riches. “Now,” he said, “there are two sorts of riches—one actual, and the other potential. A man is actually and truly rich according to what he eateth, drinketh, weareth, or in any other way really and actually enjoyeth. Others are but potentially and imaginatively rich, who though they have power over much, make little use of it, these being rather stewards and exchangers for the other sort than owners for themselves.” He then showed how he considered that “every man ought to contribute according to what he taketh to himself, and actually enjoyeth.”

In 1674 Sir William Petty published a paper on “Duplicate Proportion,” and in 1679 he published in Latin a “Colloquy of David with his Own Soul.” In 1682 he published a tract called “Quantulumcunque, concerning Money;” and “England’s Guide to Industry,” in 1686. From 1682 to 1687, the year of his death, Sir William Petty was drawing great attention to the “Essays on Political Arithmetic,” which are here reprinted. There was the little “Essay in Political Arithmetic, concerning the People, Housings, Hospitals of London and Paris;” published in 1682, again in French in 1686, and again in English in 1687. There was the little “Essay concerning the Multiplication of Mankind, together with an Essay on the Growth of London,” published in 1682, and again in 1683 and 1686. There was in 1683, “Another Essay in Political Arithmetic concerning the growth of the City of London.” There were “Farther Considerations on the Dublin Bills of Mortality,” in 1686; and “Five Essays on Political Arithmetic” (in French and English), “Observations upon the Cities of London and Rome,” in 1687, the last year of Sir William Petty’s life. Other writings of his were published in his lifetime, or have been published since his death. He was in the study of political economy one of the most ingenious and practical thinkers before the days of Adam Smith.

But the interest of those “Essays in Political Arithmetic” lies chiefly in the facts presented by so trustworthy an authority. London had become in the time of the Stuarts the most populous city in Europe, if not in the world. This Sir William Petty sought to prove against the doubts of foreign and other critics, and his “Political Arithmetic” was an endeavour to determine the relative strength in population of the chief cities of England, France, and Holland. His application of arithmetic in the first of these essays to a census of the population at the Day of Judgment he himself spoke of slightingly. It is a curious example of a bygone form of theological discussion. But his tables and his reasonings upon them grow in interest as he attempts his numbering of the people in the reign of James II. by collecting facts upon which his deductions might be founded. The references to the deaths by Plague in London before the cleansing of the town by the great fire of 1666 are very suggestive; and in one passage there is incidental note of delay in the coming of the Plague then due, without reckoning the change made in conditions of health by the rebuilding. Nobody knew, and no one even now can calculate, how many lives the Fire of London saved.

There was in Petty’s time no direct numbering of the people. The first census in this country was not until more than a hundred years after Sir William Petty’s death, although he points out in these essays how easily it could be established, and what useful information it would give. There was a census taken at Rome 566 years before Christ. But the first census in Great Britain was taken in 1801, under provision of an Act passed on the last day of the year 1800, to secure a numbering of the population every ten years. Ireland was not included in the return; the first census in Ireland was not until the year 1813.

Sir William Petty had to base his calculations partly upon the Bills of Mortality, which had been imperfectly begun under Elizabeth, but fell into disuse, and were revived, as a weekly record of the number of deaths, beginning on the 29th of October, 1603; notices of diseases first appeared in them in 1629. The weekly bills were published every Thursday, and any householder could have them supplied to him for four shillings a year. These essays will show how inferences as to the number of the living were drawn from the number of the dead. And even now our Political Arithmetic depends too much upon rough calculations made from the death register. It is seven years since the last census; we have lost count of the changes in our population to a very great extent, and have to wait three years before our reckoning can be made sure. The interval should be reduced to five years.