The idea that a legal rule can be legitimised by its economic impact is not new. The fascinating work of a historian and a sociologist shows that this legitimisation by economic calculation permeated debates on slavery in France in the 18th and 19th centuries. This book sheds invaluable historical light on the current debates on European regulation.

Slavery played only a marginal role in mediaeval Europe. It became economically important once again in the transition to capitalism. Based on the slave trade, the trade triangle played a vital role in the accumulation of capital and in the shift of the centre of economic gravity from the Mediterranean to the Atlantic. The mechanism was simple: black slaves taken by force from the African continent formed the bulk of the labour for the most dynamic capitalist sectors in the American colonies. The profits from the trade were invested in Europe, which found an outlet for its goods on the American continent. The development of the ports on the Atlantic seaboard, from Bordeaux to Liverpool, made a significant contribution to the industrial revolution.

The abolitionists had excellent moral and philosophical arguments against slavery. However, they felt – based on their beliefs or for tactical purposes, depending on the situation – that they needed an economic argument based on calculations. In their view, a mathematical assessment was an important stage in developing the link between fairness and usefulness. The first economist to consider this issue was Du Pont de Nemours in an article published in 1771. He wanted to demonstrate the absurdity of slavery through an economic calculation. His goal was to show that this system was "appalling for its victims, and harmful and ruinous for its perpetrators". In order to convince plantation owners, he needed evidence that the true cost of slave labour was higher than that of paid labour.

As with all macroeconomic research that looks not at the reality but at the potential impact of a project, his calculations relied on highly debatable assumptions. No one could clearly determine what the wages of a free workforce would be, nor what productivity would be achieved by plantations if their masters were deprived of the whip. Another economist, Turgot, threw himself into the debate by stating that Du Pont had underestimated the cost of paid labour in the West Indies. Other calculations were proposed by Condorcet, Ladebat and Frossard. For their part, the supporters of slavery looked to produce their own calculations. They underlined that, when all was said and done, both slavery and employment always resulted in situations of forced labour. Three decades later, Jean-Baptiste Say offered his assessment on other bases, but without conclusive results ...

As the contributions multiplied, the fact could not be ignored that many parameters could be taken into account. Each one further increased the degree of uncertainty. Summarising the long-running debates, the historian Augustin Cochin concluded in 1848: "But what did slave labour cost? What would free labour cost? There was no way of knowing; the formula was ingenious, and the components of the calculation were pure hypotheses".

In the end it was not an economic calculation but arms that settled the matter. Uprisings by black slaves shook the western part of the island of Saint-Domingue (now Haiti) from 1791 onwards. Over a period of 13 years, the revolution instigated by former slaves gradually gained ground over the machinations of the European powers and led to the defeat of both the British army and Napoleon’s expeditionary force. It was this revolution that opened the door to the abolition of slavery on the American continent.

Calcul et morale. Coûts de l’esclavage et valeurs de l’émancipation (XVIIIe-XIXe siècle). C. Oudin-Bastide and Ph. Steiner, Albin Michel, Paris, 2015.

Authoritative work on the slave revolution: The Black Jacobins: Toussaint L’Ouverture and the San Domingo Revolution. C.L.R. James, Vintage, New York, 1989.


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Should slavery be abolished?