Sean Byrne writes: This year marks the 350th anniversary of the appointment of St Oliver Plunkett as Archbishop of Armagh in 1669. Plunkett was then aged forty-six, two years older than Sir William Petty, who at that time was in Ireland attempting to manage some of the 270,000 acres of land in counties Kerry, Limerick, Cork, Offaly and Westmeath which he had acquired while surveying the lands of the Gaelic aristocracy which Cromwell had seized to give to his soldiers and to the English funders of his army.
Though is unlikely they ever met, William Petty and Oliver Plunkett were connected by the brutal forces of seventeenth century Irish history, which brought Petty great wealth and Plunkett martyrdom. Petty, who was a doctor, scientist, philosopher and economist, came to Ireland as physician to Cromwell’s army in 1649 and was given the task of surveying the confiscated estates of those who had supported the Irish Confederacy. Petty’s sister Dorothy was married to William Napier, whose family had been in Meath from the Elizabethan conquest and Petty arranged that Napier be given the estates confiscated from Oliver Plunkett’s Catholic family for their support of the Irish Confederacy of the 1640s.
At the time of the dispossession of his family, Oliver Plunkett was studying for the priesthood in Rome. He would subsequently return to Ireland to minister, sometimes at the risk of his life, to Catholics oppressed by the Penal Laws. Between the Restoration of Charles II in 1660 and the Popish Plot of 1678 the Penal Laws had not been rigidly enforced and Archbishop Plunkett established a Jesuit college in Drogheda, forty of whose 150 pupils were Protestant. In 1673 the English parliament enacted the Test Act “for preventing dangers which may happen from Popish recusants”. This Act required all holding public office to take communion in the Church of England and to abjure belief in transubstantiation. Plunkett rejected the Test Act and his college was closed and demolished. He went into hiding, but was not pursued until Titus Oates, an inveterate liar and fraud who had gained an appointment as a vicar by falsely claiming to have a degree from Cambridge, alleged that a group of leading English Catholics were plotting to assassinate Charles II. This group, Oates asserted, included Archbishop Plunkett of Armagh and Archbishop Talbot of Dublin.
The English parliament, fearing than an Irish jury would not convict Plunkett, brought him to London for trial. Although many involved in the trial, including the king, knew Plunkett to be innocent, he was convicted of treason. Charles II, believed to be himself secretly a Catholic, was asked by Louis XIV to spare Plunkett’s life but, fearing the wrath of his Protestant parliament, did not commute the death sentence and Plunkett was hanged, drawn and quartered at Tyburn on July 1st, 1681.
At the time of Plunkett’s execution, the Napiers were peacefully enjoying the Plunkett’s confiscated lands but Petty was involved in court cases relating to his vast estates, some of which he was accused of acquiring fraudulently. He eventually held onto a mere 50,000 acres in Kerry (all the land that could be seen from Mangerton mountain). His daughter Anne married Thomas Fitzmaurice, first Earl of Kerry and their grandson became the first Marquess of Lansdowne.
Petty was one of the originators of “Political Arithmetic”, the forerunner of modern quantitative economics, and made the first serious estimate of the population of Ireland. His Observations on the Dublin Bills of Mortality and the State of that City (1683) contains the first attempt to estimate birth and death rates and relate them to population growth. Petty was a practical political economist rather than a theorist. He anticipated the problems of valuing human life which is central to modern cost benefit analysis, when in The Political Anatomy of Ireland (1691) he valued Irish lives lost in the Cromwellian invasion as being of the price “at which slaves and negroes are usually rated, viz, about £15”.
A portrait of Petty painted in 1650 shows him holding a human skull, indicating his interest in anatomy. Had he been present when the body of St Oliver Plunkett was quartered, he might have sought to dissect it, as he would have considered this acceptable treatment for the body of a traitor. He would no doubt also have carefully examined Plunkett’s skull, now venerated in a shrine in St Peter’s Church in Drogheda.