On Saturday 7 July 1688 William Molyneux (1656-1698) wrote a letter to John Locke (1623-1704) setting out for the first time his problem concerning the person born blind:


Dublin July. 7. 88

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 stretchd out his Hand, whether he Could not Reach them, tho they were Removed 20 or 1000 feet from him?

If the Learned and Ingenious Author of the Forementiond Treatise think this problem Worth his Consideration and Answer, He may at any time Direct it to One That Much Esteems him, and is


His Humble Servant
William Molyneux
High Ormonds Gate in Dublin. Ireland




A problem about correlating visual and tactual perception, one of several that William Molyneux of Dublin posed in letters to John Locke. (Molyneux was also interested in the visual perception of distance.) Suppose that a blind person who can distinguish spheres from cubes by touch suddenly becomes able to see. Will this person be able to distinguish these shapes visually before correlating sight and touch? Locke (Essay Concerning Human Understanding, ii. ix. 8) and Berkeley (Essay Towards a New Theory of Vision, sects. 121-46) answer negatively.Berkeley went on to deny that sight and touch ever perceive the same property, strictly speaking. Leibniz (New Essays Concerning Human Understanding, sections that correspond to Locke) answers positively on the basis of structural properties in common to tactual and visible shapes. Careful empirical observations of patients who acquired vision by surgery, such as cataract removal, have not resolved the Molyneux problem. [Internet commentator]