A Treatise on the Eye/Book 5/Chapter 7
CHAP VII.
Of the Figure of Objects.
Sect.
Pag.
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| 1. | How we perceive the Figure of Objects, explained from what has been said of their Situation, | 413 |
| 2. | Mr. Molyneux's famous Question to Mr. Locke answered, contrary to the Opinion of both these great Philosophers, | 414 |
CHAP. VII.
Of the Figure of Objects.
Sect. 1. THE Seventh Phænomenon of Vision, is the Figure of Objects. This, after what hath been said, scarce needs any Explanation; for the Figure of a Body is nothing but the relative Situation of the several Parts of its Surface, that limit or terminate its Extension; some are nearer, others farther off; some are straight before us, others are on the upper, lower, right or lef tSide; and therefore, to judge of the Figure of Objects, nothing is required, but to judge of the Distance and Situation of their several Parts. But this we have already accounted for; and therefore, without saying any thing further upon it, I shall pass to the Consideration of Mr. Molyneux's ingenious Question, which he proposed to Mr Locke, namely,
§ 2. "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 Blindman to be 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 this Question, both these profound Philosophers pronounce in the negative, and are of Opinion that the Blind-man would not by Sight alone be able to say with Certainty which was the Globe which the Cube; and yet, notwithstanding the great Deference I have for the Opinion of so able Judges, I cannot help thinking that they must be mistaken; for, I have already demonstrated, that the Judgments we form of the Situation and Distance of visual Objects depend not on Custom and Experience, but on an original, connate and immutable Law, to which our Minds have been subjected from the Time they were first united to our Bodies and therefore the blind Person, immediately upon receiving his Sight, must, by virtue of this Law, by his Eyes alone, without any Assistance from his other Senses, immediately judge of the Situation of all the Parts of the Globe and Cube, and, by seeing them in the Place where they are, must receive an Idea of the Figure of those Bodies, from which he will be able to tell which is the Globe, and which the Cube: For the Idea which a blind Man must needs form of a Globe by his Touch, will be this, that it is a Body which is exactly alike on all Sides; for, let him roll it as often as he will between his Hands, he can find no Manner of Difference between the one Side and the other: But this is the very Idea which at first Sight such a Man will form of it by his Eyes, and consequently he must at first Sight know it to be a Globe, and not a Cube.
In like Manner, the Idea which a blind Man, by his Touch, forms of a Cube, must be, that it is a Body which is not alike in every Part of its Surface; for, in one Part, he feels a smooth Flat, in another, a sharp Point of an Angle, and in a third, a long Ridge, which reaches from one Angle to another; and this is the precise Idea, which, upon the first View, such a Man will frame of it by Sight; and therefore, at first Sight, he will know it to be a Cube, and not a Globe.
He will not indeed, by Sight alone, be able to tell whether what he sees will affect the Touch with an Idea of Solidity and Resistance; for what he sees may, for any Thing he can know by Sight, be like the Image seen behind a looking Glass, which does not at all affect the Touch; but if the Words Globe and Cube are understood to include nothing but Figure, abstracted from all other tactile Qualities, he must at first Sight, by seeing all the Parts of the Figure in the Place where they are, know the Globe and the Cube, and be able to distinguish them by their proper Names.