Sidney Bradford

Recovery from blindness is the phenomenon of a blind person gaining the ability to see, usually as a result of medical treatment. As a thought experiment, the phenomenon is usually referred to as Molyneux's problem. The first published human case was reported in 1728 by the surgeon William Cheselden. Patients who experience dramatic recovery from blindness experience significant to total agnosia, having serious confusion with their visual perception.

The phenomenon has often been presented in empiricism as a thought experiment, in order to describe the knowledge gained from senses, and question the correlation between different senses.

John Locke, an 18th-century philosopher, speculated that if a blind person developed vision, he would not at first connect his idea of a shape with the sight of a shape. That is, if asked which was the cube and which was the sphere, he would not be able to do so, or even guess.

The question was originally posed to him by philosopher William Molyneux, whose wife was blind:

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 the other, which is the cube, which is the sphere. Suppose then the cube and the sphere placed on a table, and the blind man made to see: query, Whether by his sight, before he touched them, he could now distinguish and tell which is the globe, which the cube? To which the acute and judicious proposer answers: ‘Not. For though he has obtained the experience of how a globe, and how a cube, affects his touch; yet he has not yet attained the experience, that what affects his touch so or so, must affect his sight so or so…’

In 1709, in A New Theory of Vision, George Berkeley also concluded that there was no necessary connection between a tactile world and a sight world—that a connection between them could be established only on the basis of experience. He speculated:

the objects to which he had hitherto used to apply the terms up and down, high and low, were such as only affected or were in some way perceived by touch; but the proper objects of vision make a new set of ideas, perfectly distinct and different from the former, and which can in no sort make themselves perceived by touch (sect. 95).

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