Here's the classic reference to the problem in Locke (which vindicates Locke's speculative answer here): http://books.google.com/books?id=vjYIAAAAQAAJ&dq=essa

Here's the classic reference to the problem in Locke (which vindicates Locke's speculative answer here): http://books.google.com/books?id=vjYIAAAAQAAJ&dq=essay%20on%20human%20understanding&pg=PA83#v=onepage&q=molineux&f=false http://books.google.com/books?id=vjYIAAAAQAAJ&dq=essay%2... > To which purpose I shall here insert a problem of that very ingenious and studious promoter of real knowledge, the learned and worthy Mr. Molineux, which he was pleased to send me in a letter some months since; and it is this: "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 the sphere. Suppose then the cube and sphere placed on a table, and the blind man made to see; quaere, 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, 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; or that a protuberant angle in the cube, that pressed his hand unequally, shall appear to his eye as it does in the cube." I agree with this thinking gentleman, whom I am proud to call my friend, in his answer to this his problem; and am of opinion, that the blind man, at first sight, would not be able, with certainty, to say, which was the globe, which the cube, whilst he only saw them; though he could, unerringly, name them by his touch, and certainly distinguish them by the difference of their figures felt.