Determinism and Enlightenment: the collaboration of Diderot and d’Holbach

Ruggero Sciuto’s Determinism and Enlightenment: the collaboration of Diderot and d’Holbach is the April volume in the Oxford University Studies in the Enlightenment series. This book examines the theory of determinism jointly put forward by Diderot and d’Holbach to better understand their philosophy as well as their position relative both to one another and to the so-called ‘Radical Enlightenment’. In this blog post, Ruggero Sciuto provides a short introduction to the main issues discussed in the volume.

They were born ten years apart, one in Langres, Haute-Marne, in 1713, the other in Edesheim, Rhineland-Palatinate, in 1723. A four-hour car ride today; in all respects a much more significant distance by eighteenth-century standards. They ended up buried one next to the other, in a small chapel in the Parisian church of Saint-Roch. Despite occasional squabbles and misunderstandings, Denis Diderot and Baron Paul Thiry d’Holbach, two of the most brilliant minds of their century, were very close collaborators. It is not just that Diderot read some of d’Holbach’s works before publication – that he washed the baron’s ‘dirty rags’, as Diderot himself put it. It is not just that both writers collaborated on such iconic, monumental texts of early-modern Europe as the Encyclopédie and the Histoire des deux Indes. Day after day, in Paris or at d’Holbach’s country house in Sucy-en-Brie (the now destroyed château du Grandval), our two authors engaged in lively discussions that informed their atheist, materialist, and deterministic philosophical views.

‘Comme Jacques et son maître, Diderot et d’Holbach ne peuvent pas aller l’un sans l’autre’, wrote Yves Benot in 1981.^[1] Of course, the one is not the other. And yet scholars have perhaps insisted more than necessary on their alterity. Dogmatic is arguably the adjective that is most commonly associated with d’Holbach.^[2] And sure enough, in his rejection of superstition and religious fanaticism, the baron is often as dogmatic and intransigent as some of the clerics against whom he so vehemently fulminates. When it comes to philosophy, too, d’Holbach may easily come across as dogmatic: seemingly blinded by his systematic aspirations, he appears to proceed at full speed and to disregard any objections as nonsensical. And yet two points ought to be made. First: the formidable machine that is d’Holbach’s style is specifically designed to convince, even mesmerise the reader and conceal any hesitations and underlying inconsistencies.^[3] Second: the apparent rigidity of his thinking is in no way indicative of a simple understanding of reality. If, as beautifully argued by Pierre Saint-Amand, Diderot is indeed a penseur de la complexité, the same can and should be said of d’Holbach.^[4]

The situation with Diderot is symmetrical. Many recent studies (I am thinking primarily of books and articles by Jean-Claude Bourdin, Colas Duflo, Gerhardt Stenger, Marian Hobson, Marx Wartofsky, Timo Kaitaro, Caroline Warman, and Eric-Emmanuel Schmitt) have finally rectified the old interpretation, most famously expressed by Yvon Belaval and Robert Loyalty Cru, according to which Diderot would be too disconnected, inconsistent, and unoriginal a philosopher truly to deserve a place in the pantheon of Philosophy proper. And yet, because of the complexity of his works, in particular because of the light, playful tone that he adopts in many of them, the inner consistency of Diderot’s thought – its ‘secret unity’, as Francis Pruner would have it – still remains too often ignored.^[5]

Adopting a comparative, to an extent synthetic, methodology that is fundamentally in keeping with Diderot’s ‘analogy-seeking mode of thought’, my new book unveils precisely some hidden similarities between Diderot’s and d’Holbach’s ideas.^[6] It does so by looking specifically at the theory of determinism that, I argue, the two philosophers jointly put forward, a theory that seeks to combine a fairly traditional form of causal determinism based on a strong interpretation of causation as necessitation with a nascent nomological determinism with laws of nature at its core.

This theory, I suggest, draws on a number of different sources, including many Christian ones, manipulating and reinterpreting them to create a harmonious new whole. It addresses many criticisms that were commonly levelled against determinism, takes shape in response to external philosophical stimuli – most notably the publication of Hume’s works, with their famous, yet not unequivocal reinterpretation of the notion of causation –, and bears the marks of a resolute attempt to reconcile the often-contrasted notions of necessity and becoming, offering new and articulate responses to questions that are still very much debated today.

In as much as it brings to light Diderot’s and d’Holbach’s links with the Christian philosophical tradition, this book also problematises the two philosophers’ atheism, further questioning the notion that the so-called ‘Radical Enlightenment’ can be taken to represent a complete break with ‘the old’. Perhaps counterintuitively, at the same time as it brings Diderot and d’Holbach closer to one another, my book takes the two philosophers farther away from Jonathan Israel’s ‘Radical Enlightenment’. It is not that I question Diderot’s and d’Holbach’s radicalism. Quite the contrary: as I write this blog I am starting to work on a new monograph project tracing the reception of d’Holbach’s political ideas in Revolutionary France! Indeed, I share Israel’s belief that the Radical Enlightenment (or eighteenth-century culture more broadly) may hold the key to countering some of the most dangerous threats that our modern democracies have to face: fundamentalism and intellectual apathy. And yet, if it does so, it is not because of its supposedly fully coherent rationalist and uncompromising philosophy. It is because of its malleability and openness to dialogue.

Diderot and d’Holbach’s philosophical dialogue is part and parcel of a much broader conversation that joins together a wide array of Enlightenment thinkers. For, as noted by Dorinda Outram and Antoine Lilti, the Enlightenment is best characterised as a series of debates around key themes and concepts, rather than as a single movement with a well-defined intellectual agenda.^[7] The set of keywords related to causation that lie at the heart of my book – cause, reason, necessity, machine, law, freedom – are frequently noted and even celebrated in isolation as slogans of Enlightenment. But considering them as interlinked concepts that thinkers used to formulate dynamic ideas about how the world works can refresh and transform our views of Enlightenment thought. Unveiling this hidden language can help us, I believe, to grasp better than ever before the why and the how of Enlightenment philosophy and literature.

This blog was originally posted on the Voltaire Foundation blog, 20 April 2023.