Le Partage de l’empirisme: une histoire du problème de Molyneux aux XVIIe et XVIIIe siècles par Marion Chottin (review)

If a blind man recovered his sight, could he distinguish through it two three-dimensional shapes that he had known previously only by touch? This thought experiment is the Molyneux problem, named for the Irish philosopher who introduced it to Locke, who in turn would make the question famous in his Essay Concerning Human Understanding. Marion Chottin demonstrates in this book that William Molyneux’s ‘jocose’ (p. 9) question was neither a shibboleth for distinguishing rationalists from empiricists, nor a vehicle for illustrating pre-established systems, but was a catalyst for a century of innovations in empiricist philosophy. The book’s structure is designed to mimic the analytical method Molyneux’s problem enabled. In a first, regressive phase, we follow Descartes, Locke, Leibniz, Berkeley, La Mettrie, Diderot, and Condillac to the headwaters of perception, with the blind man’s first sight serving as a moment of ‘genesis’ in which pure visual sensation can be considered in isolation from association with other senses. The second, progressive phase shows how the same thinkers theorize the process that leads from this genetic moment towards a unified perceptual phenomenon of the world. Chottin argues that Molyneux’s question could only have been posed from the late seventeenth century onward: Kepler’s optics had introduced a distinction between our perception and objects in the world by postulating that light projects ‘retinal paintings’ into the eye. This distinction, along with Gassendi’s objections to Descartes’s theory of vision, and Locke’s embrace of the senses as the source of all knowledge, were necessary precursors for the question of the blind man made sighted. Locke and Berkeley both answered ‘no’ to the question, maintaining that what we perceive is the result of our judgement, tempered by experience, acting on sensations to produce a unified phenomenon; thus the immediate sensation of a ‘variously shaded’ two-dimensional circle becomes a perception of a three-dimensional sphere. La Mettrie and Diderot will disagree, rejecting the idea that unperceived judgements can play any role in creating knowledge. They maintain instead that sensation itself transforms through recognition, during a process of ‘éducation sensorielle’. Condillac goes further in his Traité des sensations, refusing any identification of sensations with knowledge or ideas: visual sensation is an undifferentiated whole, and cannot be the locus of knowledge—only our thoughts can. By the century’s end, the Molyneux problem ceased to be a motor of empiricist innovation, considered by Kant to be a question for empirical science, not speculative philosophy. Chottin’s detailed philosophical history is an achievement partly because it is thoroughly historicizing. She gives ample consideration to the evolving intellectual and material conditions in which theories were produced, and highlights the dialogic nature of philosophical enquiry, showing how thinkers responded to one another. This quality, and the book’s regressive–progressive structure, can sometimes lead to a sense of repetition, but this proves useful in keeping up with the author’s subtle analysis of intricate argumentation. A creeping suspicion does build as one reads that things cannot possibly be as neat as they are presented. Everything is cleanly schematized, often in handy groupings of three—one has to ask how much Chottin’s own judgement has shaped her perception of historical data here. Still, the evidence is thorough and incisive, and the arguments convincing: this book is a major contribution to the history of an important idea.