Sensibility as Vital Force or as Property of Matter in Mid-Eighteenth-Century Debates

Sensibility, whether understood in moral, physical, medical or aesthetic terms, seems to be a paramount case of a higher-level, intentional property, not a basic property. Diderot famously claimed that matter itself senses, with sensibility being a general or universal property of matter, even if he sometimes stepped back from this claim and called it a “supposition.” Crucially, sensibility here is a ‘booster’: it enables materialism to account for the phenomena of conscious, sentient life, contrary to what its opponents hold, for if matter can sense, and sensibility is not a merely mechanical process, then the loftiest cognitive plateaus belong to one and the same world as the rest of matter. Lelarge de Lignac noted this when he criticized Buffon for “granting to the body [la machine, a then-common term for the body] a quality which is essential to minds, namely sensibility.” This view, which Diderot definitely held, was comparatively rare, stemming from medico-physiological sources including Robert Whytt, Albrecht von Haller and Théophile de Bordeu. We then have, I suggest, an intellectual landscape in which newly articulated properties such as irritability and sensibility are presented either as an experimental property of muscle fibers to be understood mechanistically (Hallerian irritability) or a property of matter itself (whether specifically living matter as in Bordeu and his fellow montpelliérains Ménuret and Fouquet, or matter in general, as in Diderot). I am not convinced that their debates involve an identical concept, but nevertheless propose a topography of the problem of sensibility as property of matter or as vital force in mid-eighteenth-century debates – not an exhaustive cartography of all possible theories, but an attempt to understand the ‘triangulation’ of three views: a vitalist view in which sensibility is fundamental, matching up with a conception of the organism as the sum of parts conceived as little lives (Bordeu et al.); a broadly mechanist view which builds upwards, step by step, from the basic property of irritability to the higher-level property of sensibility (Haller); and, more eclectic, a materialist view which seeks to combine the explanatory force of the Hallerian approach with the metaphysically explosive (monistic) potential of the vitalist approach (Diderot). Examining Diderot in the context of this triangulated topography of sensibility as property should shed light on his famous proclamation regarding sensibility as a universal property of matter.