Molyneux’s Problem — Stanford Encyclopedia of Philosophy (Summer 2024)
Source
Degenaar, M. & Lokhorst, G.J. (2024). Molyneux’s Problem. In E.N. Zalta & U. Nodelman (Eds.), The Stanford Encyclopedia of Philosophy (Summer 2024 Edition). https://plato.stanford.edu/archives/sum2024/entries/molyneux-problem/
First published June 30, 2005; substantive revision November 23, 2021.
Core Problem Statement
Original Formulation (Molyneux to Locke, July 7, 1688)
“A Problem Proposed to the Author of the Essai Philosophique concernant L’Entendement: A Man, being born blind, and having a Globe and a Cube, nigh of the same bignes, Committed into his Hands, and being taught or Told, which is Called the Globe, and which the Cube, so as easily to distinguish them by his Touch or Feeling; Then both being taken from Him, and Laid on a Table, Let us Suppose his Sight Restored to Him; Whether he Could, by his Sight, and before he touch them, know which is the Globe and which the Cube? Or Whether he Could know by his Sight, before he stretch’d out his Hand, whether he Could not Reach them, tho they were Removed 20 or 1000 feet from Him?”
Locke’s Published Version (1694, Essay 2nd Edition)
“Suppose a Man born blind, and now adult, and taught by his touch to distinguish between a Cube, and a Sphere of the same metal, and nighly of the same bigness, so as to tell, when he felt one and t’other; which is the Cube, which the Sphere. Suppose then the Cube and Sphere placed on a Table, and the Blind Man to be made to see. Quaere, Whether by his sight, before he touch’d them, he could now distinguish, and tell, which is the Globe, which the Cube.”
Historical Context
Origin: William Molyneux (1656-1698), Irish scientist/politician, inspired by Locke’s Essay extract (1688) on ideas from single vs. multiple senses. Personal motivation: Molyneux’s wife lost her sight in their first year of marriage. Possible earlier influence: Ibn Tufail’s Hayy ibn Yaqdhan (12th century) but no evidence Molyneux read it.
18th-Century Philosophical Positions
Negative (no): Molyneux, Locke, Berkeley — empiricist view that visual/tactual relation is arbitrary, learned by experience. Affirmative (yes): Synge, Lee, Leibniz — rationalist view that relation is necessary and perceived directly or by reason. Mixed: Reid — visual/tactual notions differ but can be related by reason.
First Experimental Data: Cheselden (1728)
Surgeon William Cheselden operated on Daniel Dolins, a congenitally blind patient with cataracts. Findings: boy could not distinguish shapes by sight initially; could not recognize objects regardless of shape/magnitude differences. Interpretations varied: Voltaire/Camper/Condillac saw confirmation of Berkeley; La Mettrie/Diderot noted confounding factors (eyes not functioning properly post-surgery, insufficient recovery time, leading questions).
19th-Century Developments
New approaches: cataract patient studies (conflicting results); animal studies (Adam Smith, Johannes Muller — some animals see at birth, supporting affirmative answer); infant studies (Thomas Brown — babies must learn to see, supporting negative); Wheatstone’s discovery of immediate 3D space perception supporting affirmative answer.
Modern Approaches
Historical analysis, clinical studies of recovery from early blindness, visual deprivation experiments in animals (critical period), sensory substitution devices. Molyneux’s experiment has never been satisfactorily performed.