Analysis: William Petty's use of numerical information about land and people shows that there are no such things as simple or neutral facts

Numbers and statistics have acquired a grim importance and urgency of late thanks to the pandemic. We have very quickly become familiar with forms of analysis used by epidemiologists, scientists who study health at the level of populations, rather than individuals. We can discuss rates of infection, mortality rates, positivity rates, and we anxiously track deaths per million or per 100,000. A sobering league table has emerged, that no country wants to lead. These numbers and statistics are vital to our understanding of this new disease, and to our ability to tackle it. 

But the framing of death and disease in terms of numbers, rather than individuals, is also problematic. Comparing mortality rates as numbers and data erases the humanity of the individuals whose deaths make up those numbers. This was poignantly expressed by Dorothy Duffy in My sister is not a statistic’, her poem about the death of her sister from Covid-19.

The morally troubling aspect of statistics has been apparent since its emergence as a new form of knowledge. Statistics and the study of populations is usually seen as part of the scientific revolution of the 17th century, when religious interpretations of the world gave way to investigations of empirical reality and the insistence on observable facts as the basis for theories. One of the reasons that the Royal Society in England, founded in 1663, was committed to the promotion of empirically-based research was that it was regarded as a way of avoiding and moving beyond the religious and philosophical disputes that had raged since the Reformation.

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From Marginal Revolution University, an introduction to the work of William Petty

However, it is very tricky to separate supposedly neutral ‘facts’ from ideological controversy, as is seen in the career of William Petty. A polymath and founder member of the Royal Society, Petty was educated in Oxford, France and the Netherlands and came to Ireland in 1652 as physician to Oliver Cromwell's army. Petty’s wide-ranging abilities soon saw him appointed to other duties, including the redistribution of Catholic-owned lands seized during Cromwell’s campaign. This resulted in the first attempt at a comprehensive survey of land and population in Ireland, usually referred to as the ‘Down Survey’.

The fact that the surveying and mapping of land was frequently prompted by the concerns of the military, or in the context of the seizure and settlement of land, is no great secret in Ireland. Many people are familiar with Brian Friel’s play Translations, which represents the 19th-century ordnance survey project as both an outcome of colonization and a further act of erasure of Irish culture through the replacement of place names with anglicized equivalents. It is less well known that population statistics had a very similar point of origin.

English administrations in Ireland, such as the one of which Petty was a part, were obviously keen to maximize the productivity of the land. Doing so both contributed to individual and state coffers and served the ideological function of proving that the country and its people were better off under the guidance of a civilized and ‘improving’ regime.

The confluence of statistical science with sectarianism and colonial ideas of productivity and value continued into the 18th century

Petty was among the very first writers to recognise the importance of gathering numerical information about land and people in order to bolster this project through the application of the new scientific method, founded on ‘facts’. He even gave his new science a new name: ‘Political Arithmetic’. One of the key principles of political arithmetic was that population size was a key indication of the growing wealth of a nation, and thus his Political Anatomy of Ireland (1691) gives a great deal of space to calculating population from the very patchy information available, frequently relying on estimates of births and deaths.

But it is clear from Petty’s work that not all lives ‘count’ the same. Because his study of population and population increase is motivated by concerns about productivity and wealth, he distinguishes between those capable of work, or women capable of childbearing, and those who are not ‘productive’, effectively ‘subtracting’ from his totals the elderly and infirm, and children ‘not fit for labour’. Sectarianism was also embedded in the thought of the period, and Petty’s figures therefore also include estimates of the numbers of Catholics, Anglicans and dissenting Protestants in Ireland, not only in the interests of accuracy, but also because Catholics were generally regarded as lazier and less productive.

The confluence of statistical science with sectarianism and colonial ideas of productivity and value that we see in Petty continued into the 18th century. In his Essay on the Trade and Improvement of Ireland (1729-31), for example, Arthur Dobbs attributes population growth in Ireland to the impact of King William’s victory over James II at the Battle of the Boyne in 1690 and the consequent safeguarding of Protestant rule. However, the facts were not in Dobbs’s favour: a combination of financial instability and poor harvests in the 1720s led to great hardship and localized famines in Ireland.

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From RTÉ Radio 1's Arena, Brendan Twomey looks at A Modest Proposal, one of Jonathan Swift's most famous works

It was the gap between the rhetoric of writers like Dobbs, and the actual facts of poverty and hardship that prompted Jonathan Swift to write his savagely satirical A Modest Proposal in 1729. In what appears at first to be a pamphlet on ways to 'improve' Ireland economically, Swift declared that Ireland was an anomaly, because it was a country in which an increase in population did not signal wealth, but in fact lead to even greater poverty.

The solution, or ‘modest proposal’, that he outlined was simple: to reduce the population and address poverty, the poor should be encouraged to sell their infant children to the rich as food. Swift’s pamphlet is astonishingly prescient in the way it identifies the potential for dehumanization that lurked within the new ‘scientific’ methods for counting and categorizing people.

The reasons for gathering statistics also shape the knowledge and understanding they offer

Since the start of the pandemic, we have been confronted with the uncomfortable implications of similar forms of arithmetic. Deaths are categorized by age, and by ‘underlying condition’. These categorizations are essential to understanding how the disease works, and who is most at risk, but the focus on the relatively low risks to the younger and healthier seems to suggest that some lives are less valuable, and some deaths less significant.

William Petty pioneered the use of statistics as a vital form of knowledge, but his work also reveals that there are no such things as simple or neutral facts. The reasons for gathering statistics also shape the knowledge and understanding they offer, and our values play a vital role in the use we make of statistical knowledge.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ