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per, as the proper eye,) do loudly and utterly explode the assumption, that we can perceive "merely color without figure or extension ;" and I confidently rest, that the evidence is beyond all gainsay:—but it remains for any authority to show whereon it still holds, that we perceive “external objects themselves.

NOW, ELSE, IT IS AN IMPREGNABLE FACT, OF PRODIGIOUS MAGNITUDE, THAT WE ARE EXTENDED THINGS:-AND, THOSE THINGS WHICH IMPRESS US ARE LIKEWISE EXTENDED.—Let men, therefore, turn from a fruitless waste of learning, in denying a truth so irresistible; and advance rationally to explode the dismal error of adopting a cerebral mind merely organic. The evidences for a distinct mind are many, and mighty; while those for its extension, are higher than any demonstration. Upon this I have grounded the conjecture of a spherule percipient, which operates by. an undulating surface ; treated in that essay to which I have already referred, as my principal effort to open a most desirable prospect.

PARAMOUNT PROOF OF THE NATURE OF

PERCEIVED FIGURE.

The matter treated in the two last pages was printed some months ago; and has since become more interesting on account of that important case mentioned in my preface. If that case is supposed to uphold Reid's doctrine, that it is possible to know color, without perception of extension at all, I confidently pronounce it absurd ; and here appeal to my last argument. I have no room to enlarge, but must pass on to evidence of a very different character from all the foregoing.

First let me observe, that all existing theories of perception have one great fault, in pot describing, precisely, the relations between perceived figure and its sensation. The hitherto insuperable difficulty of this, is evident in the controversy of Reid with Berkeley.

Berkeley's great assumption is, that visible extension, and figure, are mere sensations inextended in the mind : while Reid affirms they are not sensations and not in the mind; but really external, and extended.

Upon this difference I must say, that visible extension, and figure, are certainly in the mind: and I farther agree with Berkeley, that every visible extension, within figure, is at least colored. Now I have, in another work, argued that the real extension of color is proved, by the co-existence of several colors. But my object here is not field extension, but only figure ; and, if I am not mistaken, visible figure is not colored, but exists only in the prication of all color. If so, it is perceived in a way extremely different from the field of extension within it.

Suppose we look at the moon, contrasted with blue sky: I ask how do we perceive what we call her apparent shupe? The surface we perceive, truly is colored ; and if the boundary line that gives the shupe be a sensation, it also nust be colored: But evidently it has no color. In other words, her supposed figure is not sensation, por even is it colored like sensation. If we suppose the extreme verge of white to be the figure, this is a gross absurdity. since it is only part of the surface, and not the limit of the white: And the same objection holds if we take any rim of surface from the blue sky.

Again, If we hold up a hair against the sky, it gives color, which kas width: but this constitutes no figure, and the narrow hair is perceived only by aid of two widthless lines, without which it must spread infinitely both ways. To enlarge the experiment, if instead of a hair we hold up a broad black ruler, either of its edges will seem joined with the sky : but the line of junction is neither black, nor blue: it has no width, and yet it is perfectly well defined. It is figure, but not sensation.

But now a great question arises, to what does this widthless line belong? And here, if it belong to either the ruler, or the sky, it must appear colored, and have width: but it plainly has neither, and therefore cannot be an external thing. Besides this argument, we are conscious that the line belongs to no one color exclusivety, but is common between the two sensations, and is the thing that makes two of them. Therefore wherever the two sensations co-exist, there also certainly is the line between. This fact is universal in all objects; and it forms a definite characteristic difference between these two closely allied things, sensation of color, and perceived figure.

But it is farther highly important that there is also a well defined characteristic difference between perceived figure, and its corresponding external figure. For we kuow that every external body has a figure exclusively its own: but, however prodigious it may sound, I assert that no visible object in all nature. (i. e. as perceived by us) has any figure exclusively its own. All visible figures are perceived only by the addition af some field of extended color beyond them. A house, or a tree, may represent them all; and if we look at a tree, with a wall, or with the sky beyond it, we habitually think that the figure we see, is that of the tree erclusively. But, in truth, it no more belongs to the tree, than to the sky beyond. If it belong to the tree, it must appear green ; Or, if to the sky, it must appear sky color: but it appears neither. Therefore, though the sky be many miles beyond the tree, yet one line is common between both the perceived colors, and belongs exclusively to neither. To attempt to refute this with a microscope would only illustrate its unalterable nature.

Thus no visible object has any figure exclusively its own ; for every two adjoining ones have but one line to serve both. Now this is quite a different character from that of external bodies, each of which has a figure exclusively its own; and thus it is demonstrated, that perceived figure is not external figure. Besides this argument, I must repeat, we are conscious that every two co-existing contrasted colors, are lined at their change; and it is self-evident that where the sensations are, there also must be their change line. Thus, both external and internal evidence completely demonstrate my assumed position.

Visible figure, then, is not sensation, nor even colored like sensation: but it is a line really extended and mathematically void of width ; revealed to us by the junction of two contrasted sensations of color. It therefore appeals, (as I have always asserted) to consciousness, in a peculiar way. But a real line, though void of width, cannot be a line upon nothing. It must therefore have some substance, or rather seems itself substance; and this substance is demonstrated to be THE SUBSTANCE OF SENSATION. Yet more, A perceived widthless line, by returning into itself, forms figures of TWO DIMENSIONS: therefore, the substance that sustains these must be extended in two dimensions, that is, it has SURFACE.

Here I think we may rest upon evidences which appear neither to be disputed, nor traced farther : since (whatever be the character of external things) perceived figure must be what it is perceived to be ; there being no higher judge to reverse it. But, putting the peculiar character of visible figure out of the question, we may assert, as a certain proof by itself, that the term VISIBLE FIGURE is nothing but another name for the ARRANGEMENT OF OUR CO-EXISTING VISUAL SENSATIONS. Colors give pleasure : but visible figure gives

far more. - Now to say that visible figure gives delight, is only to say that the ARRANGEMENT of our co-eristing visual sensations gives delight. I think, no man will gainsay it.

Finally, I submit whether this is not the evidence, to oppose to · Berkeley's scheme, instead of taking up such a position as that of

Dr. Reid, that the notion of perceived figure only FOLLOWS the sensation; and that therefore the figure is the external tree, or moon, itself. But, had Reid recognised these evidences, in that instant the supposed inextension of the mind must have appeared to him exploded ; as it now is, I trust, for ever.

It remains for others to judge, whether this amounts to that desideratum so long wanted to show how sensation consists with perceived figure ; and how perceived figure differs from external figure.

The consequences of such a proof are immense, but the above sketch is too compressed even to do justice to the proof alone ; and I have only to hope that the lovers of truth will afford it candid con. sideration in its present state.

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