by square surfaces, and that a sphere is not terminated by square surfaces:  upon the supposition that a visible and tangible square differ only in NUMERO it follows that he might know, by the unerring mark of the square surfaces, which was the cube, and which not, while he only saw them.  We must therefore allow either that visible extension and figures are specifically distinct from tangible extension and figures, or else that the solution of this problem given by those two thoughtful and ingenious men is wrong.

134.  Much more might be laid together in proof of the proposition I have advanced:  but what has been said is, if I mistake not, sufficient to convince anyone that shall yield a reasonable attention:  and as for those that will not be at the pains of a little thought, no multiplication of words will ever suffice to make them understand the truth, or rightly conceive my meaning.

135.  I cannot let go the above-mentioned problem without some reflexion on it.  It hath been evident that a man blind from his birth would not, at first sight, denominate anything he saw by the names he had been used to appropriate to ideas of touch, VID. sect. 106.  Cube, sphere, table are words he has known applied to things perceivable by touch, but to things perfectly intangible he never knew them applied.  Those words in their wonted application always marked out to his mind bodies or solid things which were perceived by the resistance they gave:  but there is no solidity, no resistance or protrusion, perceived by sight.  In short, the ideas of sight are all new perceptions, to which there be no names annexed in his mind:  he cannot therefore understand what is said to him concerning them:  and to ask of the two bodies he saw placed on the table, which was the sphere, which the cube? were to him a question downright bantering and unintelligible; nothing he sees being able to suggest to his thoughts the idea of body, distance, or in general of anything he had already known.

136.  It is a mistake to think the same thing affects both sight and touch.  If the same angle or square which is the object of touch be also the object of vision, what should hinder the blind man at first sight from knowing it?  For though the manner wherein it affects the sight be different from that wherein it affected his touch, yet, there being beside his manner or circumstance, which is new and unknown, the angle or figure, which is old and known, he cannot choose but discern it.

137.  Visible figure and extension having been demonstrated to be of a nature entirely different and heterogeneous from tangible figure and extension, it remains that we inquire concerning.  Now that visible motion is not of the same sort with tangible motion seems to need no farther proof, it being an evident corollary from what we have shown concerning the difference there is between visible and tangible extension:  but for a more full and express proof