dictates upon their own authority, yet philosophy is not entitled to this privilege. But, that I may not dissent from so grave a personage without giving a reason, I give this as the reason of my dissent :-I see the sun when he shines; I remember the battle of Culloden ;* and neither of these objects is an image or perception.

He tells us, in the next place, "That the senses are only the inlets through which these images are received."

I know that Aristotle and the schoolmen taught that images or species flow from objects, and are let in by the senses, and strike upon the mind; but this has been so effectually refuted by Des Cartes, by Malebranche, and many others, that nobody now pretends to defend it. Reasonable men consider it as one of the most unintelligible and unmeaning parts of the ancient system. To what cause is it owing that modern philosophers are so prone to fall back into this hypothesis, as if they really believed it? For, of this proneness I could give many instances besides this of Mr Hume; and I take the cause to be, that images in the mind, and images let in by the senses, are so nearly allied, and so strictly connected, that they must stand or fall together. The old system consistently maintained both but the new system has rejected the doctrine of images let in by the senses, holding, nevertheless, that there are images in the mind; and, having made this unnatural divorce of two doctrines which ought not to be put asunder, that which they have retained often leads them back involuntarily to that which they have rejected.

an argument. Perhaps it was intended only for illustration. The argument, the only argument, follows:

The table which we see, seems to diminish as we remove farther from it; but the real table, which exists independent of us suffers no alteration. It was, therefore, nothing but its image which was presented to the mind. These are the obvious dictates of reason.

To judge of the strength of this argument, it is necessary to attend to a distinction which is familiar to those who are conversant in the mathematical sciences-I mean the distinction between real and apparent magnitude. The real magnitude of a line is measured by some known measure of length-as inches, feet, or miles: the real magnitude of a surface or solid, by known measures of surface or of capacity. This magnitude is an object of touch only, and not of sight; nor could we even have had any conception of it, without the sense of touch; and Bishop Berkeley, on that account, calls it tangible magnitude.*

Apparent magnitude is measured by the angle which an object subtends at the eye. Supposing two right lines drawn from the eye to the extremities of the object making an angle, of which the object is the subtense, the apparent magnitude is measured by this angle. [210] This apparent magnitude is an object of sight, and not of touch. Bishop Berkeley calls it visible magnitude.

If it is asked what is the apparent magnitude of the sun's diameter, the answer is, that it is about thirty-one minutes of a degree. But, if it is asked what is the real magnitude of the sun's diameter, the answer must be, so many thousand miles, or so many diameters of the earth. From which it is evident that real magnitude, and apparent magnitude, are things of a different nature, though the name of magnitude is given to both. The first has three dimensions, the last only two; the first is measured by a line, the last by an angle.

Mr Hume surely did not seriously believe that an image of sound is let in by the ear, an image of smell by the nose, an image of hardness and softness, of solidity and resistance, by the touch. For, besides the absurdity of the thing, which has often been shewn, Mr Hume, and all modern philosophers, maintain that the images which are the immediate objects of perception have no existence when they are not perceived; whereas, if they were let in by the senses, they must be, before they are perceived, and have a separate existence. [209] He tell us, farther, that philosophy teaches that the senses are unable to produce any immediate intercourse between the mind and the object. Here, I still require the reasons that philosophy gives for this; for, is altogether untenable. For, in the first place, magto my apprehension, I immediately perceive external objects, and this, I conceive is the immediate intercourse here meant. Hitherto I see nothing that can be called

The sun can be no immediate object of consciousress in perception, but only certain rays in connection with the eye. The battle of Culloden can be no immediate object of consciousness in recollection, but only a certain representation by the mind itself.-H.

From what has been said, it is evident that the real magnitude of a body must continue unchanged, while the body is unchanged. This we grant. But is it likewise evident, that the apparent mag

*The doctrine of Reid-that real magnitude or extension is the object of touch, and of touch alone

nitude appears greater or less in proportion to the different size of the tactile organ in different subjects; thus, an apple is larger to the hand of a child than to the hand of an adult. Touch, therefore, can, at best, afford a knowledge of the relation of magnitudes, in proportion to the organ of this or that individual. But, in the second place, even in the same individual, the same object appears greater or less, according as it is touched by one part of the body or by another. On this subject, see Weber's "Annotationes de Pulsu, Resorptione, Auditu et Tactu;" Leipsic, 1834.-H.

nitude must continue the same while the body is unchanged? So far otherwise, that every man who knows anything of mathematics can easily demonstrate, that the same individual object, remaining in the same place, and unchanged, must necessarily vary in its apparent magnitude, according as the point from which it is seen is more or less distant; and that its apparent length or breadth will be nearly in a reciprocal proportion to the distance of the spectator. This is as certain as the principles of geometry.*

We must likewise attend to this-that, though the real magnitude of a body is not originally an object of sight, but of touch, yet we learn by experience to judge of the real magnitude in many cases by sight. We learn by experience to judge of the distance of a body from the eye within certain limits; and, from its distance and apparent magnitude taken together, we learn to judge of its real magnitude. [211]

And this kind of judgment, by being repeated every hour and almost every minute of our lives, becomes, when we are grown up, so ready and so habitual, that it very much resembles the original perceptions of our senses, and may not improperly be called acquired perception.

Whether we call it judgment or acquired perception is a verbal difference. But it is evident that, by means of it, we often discover by one sense things which are properly and naturally the objects of another. Thus I can say, without impropriety, I hear a drum, I hear a great bell, or I hear a small bell; though it is certain that the figure or size of the sounding body is not originally an object of hearing. In like manner, we learn by experience how a body of such a real magnitude and at such a distance appears to the eye. But neither its real magnitude, nor its distance from the eye, are properly objects of sight, any more than the form of a drum or the size of a bell, are properly objects of hearing.

If these things be considered, it will appear that Mr Hume's argument hath no force to support his conclusion-nay, that it leads to a contrary conclusion. The argument is this: the table we see seems to diminish as we remove farther from it; that is, its apparent magnitude is diminished; but the real table suffers no alteration-to wit, in its real magnitude; therefore, it is

The whole confusion and difficulty in this ma'ter arises from not determining what is the true object in visual perception. This is not any distant thing, but merely the rays of light in immediate relation to the organ. We thereforesee a different object at every movement, by which a different complement of rays is reflected to the eye. The things from which these rays are reflected are not, in truth, perceived at all; and to conceive them as objects of perception is therefore erroneous, and productive of error.-H.

Let us suppose, for a moment, that it is the real table we. see: Must not this real table seem to diminish as we remove farther from it? It is demonstrable that it must. How then can this apparent diminution be an argument that it is not the real table? [212] When that which must happen to the real table, as we remove farther from it, does actually happen to the table we see, it is absurd to conclude from this, that it is not the real table we see.* It is evident, therefore, that this ingenious author has imposed upon himself by confounding real magnitude with apparent magnitude, and that his argument is a mere sophism.

I observed that Mr Hume's argument not only has no strength to support his conclusion, but that it leads to the contrary conclusion to wit, that it is the real table we see; for this plain reason, that the table we see has precisely that apparent magnitude which it is demonstrable the real table must have when placed at that distance.

This argument is made much stronger by considering that the real table may be placed successively at a thousand different distances, and, in every distance, in a thousand different positions; and it can be determined demonstratively, by the rules of geometry and perspective, what must be its apparent magnitude and apparent figure, in each of those distances and positions. Let the table be placed successively in as many of those different distances and different positions as you will, or in them all; open your eyes and you shall see a table precisely of that apparent magnitude, and that apparent figure, which the real table must have in that distance and in that position. Is not this a strong argument that it is the real table you see?*

In a word, the appearance of a visible object is infinitely diversified, according to its distance and position. The visible appearances are innumerable, when we confine ourselves to one object, and they are multiplied according to the variety of objects. Those appearances have been matter of speculation to ingenious men, at least since the time of Euclid. They have accounted for all this variety, on the supposition that the objects we see are external,

See last note.-H.

human understanding to the perception of ideas in our own minds. This power of perceiving ideas is as inexplicable as any of the powers explained by it: and the contiguity of the object contributes nothing at all to make it better understood; because there appears no connection between contiguity and perception, but what is grounded on prejudices drawn from some imagined similitude between mind and body, and from the supposition that, in perception, the object acts upon the mind, or the mind upon the object. We have seen how this theory has led philosophers to confound those operations of mind, which experience teaches all men to be different, and teaches them to distinguish in common language; and that it has led them to invent a language inconsistent with the principles upon which all language is grounded.

The last reflection I shall make upon this theory, is that the natural and necessary consequences of it furnish a just prejudice against it to every man who pays a due regard to the common sense of mankind. [216] Not to mention that it led the Pythagoreans and Plato to imagine that we see only the shadows of external things, and not the things themselves, and that it gave rise to the Peripatetic doctrine of sensible species, one of the greatest absurdities of that ancient system, let us only consider the fruits it has produced since it was newmodelled by Des Cartes. That great reformer in philosophy saw the absurdity of the doctrine of ideas coming from external objects, and refuted it effectually, after it had been received by philosophers for thousands of years; but he still retained ideas in the brain and in the mind.† Upon this foundation all our modern systems of the powers of the mind are built. And the tottering state of those fabrics, though built by skilful hands, may give a strong suspicion of the unsoundness of the foundation.

It was this theory of ideas that led Des Cartes, and those that followed him, to think it necessary to prove, by philosophical arguments, the existence of material objects. And who does not see that philosophy must make a very ridiculous figure in the eyes of sensible men, while it is employed in mustering up metaphysical arguments, to prove that there is a sun and a moon, an earth and a sea? Yet we find these truly great men, Des Cartes, Malebranche, Arnauld, and Locke, seriously employing themselves in this argument.

Surely their principles led them to think

See above, p. 262, col. b, note *-.H, ↑ See Note N.-H.

If Reid do not allow that we are immediately cognitive or conscious of the non-ego, his own doc. trine of perception differs not from that of other philosophers in the necessity for this proof.-H.

that all men, from the beginning of the world, believed the existence of these things upon insufficient grounds, and to think that they would be able to place upon a more rational foundation this universal belief of mankind.

But the misfortune is, that all the laboured arguments they have advanced, to prove the existence of those things we see and feel, are mere sophisms: Not one of them will bear examination.

I might mention several paradoxes, which Mr Locke, though by no means fond of paradoxes, was led into by this theory of ideas. [217] Such as, that the secondary qualities of body are no qualities of body at all, but sensations of the mind: That the primary qualities of body are resemblances of our sensations: That we have no notion of duration, but from the succession of ideas in our minds: That personal identity consists in consciousness; so that the same individual thinking being may make two or three different persons, and several different thinking beings make one person: That judgment is nothing but a perception of the agreement or disagreement of our ideas. Most of these paradoxes I shall have occasion to examine.

However, all these consequences of the doctrine of ideas were tolerable, compared with those which came afterwards to be discovered by Berkeley and Hume :-That there is no material world: No abstract ideas or notions: That the mind is only a train of related impressions and ideas, without any subject on which they may be impressed: That there is neither space nor time, body nor mind, but impressions and ideas only: And, to sum up all, That there is no probability, even in demonstration itself, nor any one proposition more probable than its contrary.

These are the noble fruits which have grown upon this theory of ideas, since it began to be cultivated by skilful hands. is no wonder that sensible men should be

It

disgusted at philosophy, when such wild and shocking paradoxes pass under its name. However, as these paradoxes have, with great acuteness and ingenuity, been deduced by just reasoning from the theory of ideas, they must at last bring this advantage, that positions so shocking to the common sense of mankind, and so contrary to the decisions of all our intellectual powers, will open men's eyes, and break the force of the prejudice which hath held them entangled in that theory. [218]

CHAPTER XV.

ACCOUNT OF THE SYSTEM OF LEIBNITZ.

THERE is yet another system concerning perception, of which I shall give some ac