William Molyneux, an Irish surgeon, wrote to Locke : ‘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. Suppose then the cube and the sphere were placed on a table, and the blind man made to see: query, whether by his sight, before he touched them, could he distinguish and tell which was the globe and which the cube?’ Molyneux, like Locke and Berkeley, thought the answer would be that he could not. Empirical research has produced few definitive answers, although there is evidence that in cases where a good retinal image is made suddenly available (for example after corneal grafting) immediate visual perception can take place, of objects with which the subject is familiar through touch. It may, however, take months to learn to see things not previously taught by touch, and objects such as shadows. Philosophically the question bears on the way we are to think of the relation between visual space and tactile space. In other words, the issue affects the way to think of the integration of information provided by the different senses, in the building of perceptual knowledge.
Philosophy dictionary. Academic. 2011.