The unanswered question

Decades after Descartes’ philosophical speculations about blindness in Dioptrique, a resurgence of interest in blindness occurred across the channel in England, sparking a series of celebrated debates and dialogues between intellectuals in Britain and France that included such figures as Berkeley (1709), Hutcheson (1728), Bouillier (1737), Jurin (1738), La Mettrie (1745), Condillac (1746), Diderot (1749), Reid (1764), and Leibniz (1765). What became known in the philosophy literature as either ‘Molyneux's question’ or the ‘Molyneux problem’ was regarded by the influential historian of philosophy Ernst Cassirer in 1951 as the central question of eighteenth-century epistemology and psychology (in Gallagher 2005: 153). This chapter provides more historical focus on the question and its implications, the better to justify Cassirer's claim. Of course, while Molyneux's seemingly naive and straightforward philosophical question initially concerns blindness, the question is asked hypothetically, between a philosopher and a scientist, in order to clarify the relationship between perception through the senses and the certainty of knowledge concerning objects in the world. This chapter opens with Molyneux's initial concern of his hypothetical blind man, and pursues its philosophical ramifications within the immediate context of debates between the rationalism of Descartes’ method, which looked to place reason at the heart of the philosophical and scientific enterprise, and the empiricism of his British philosophical counterparts Locke and Berkeley, who argued against the existence of any pre-existing or innate knowledge in order to see how more complex ideas and concepts can arise from simple experiences. For, prior to any recorded cataract operations or opthalmic interventions, and prior to any formation of a properly experimental psychology, this question and its immediate aftermath initiated, as we saw, a ‘proto-psychology’ in Grosrichard's (2012) words, but also sets up the philosophical framework in subsequent chapters that examine, first, the empirical and scientifically verifiable treatments of blind subjects after Cheselden's surgery in 1728, and secondly, the ensuing cross-channel epistemological debate involving Diderot, Voltaire, and others based on this and other evidence.

Although his original question in the form of a letter to John Locke in 1688 was ignored, in 1692 the Irishman William Molyneux posed the question to Locke for a second time, following the publication and success of the first edition of Locke's celebrated An Essay Concerning Human Understanding in 1690.