brain. These little parts must needs get in at the doors of our bodies, and mingle themselves with the spirits in the nerves, and, of necessity, must make some motion in the brain. Doubtless, if this be true, there must needs be an incredible motion in the brain; for, if the atoms of two armies fighting should rush into your brain by the eye, they will make a greater motion than Minerva did in Jupiter's brain. You would call for a Vulcan to cleave your head, and let out those armed men, who would cause a greater struggle in your head, than the twins did in Rebecca's womb : For I do not think these little myrinidons would lie so quiet in your brain as the Grecians did in the Trojan horse. But, if the material atoms of the object pierce the organ; as, for example, of a horse; then tell us, how many atoms must meet to make up a little horse; and how can that horse, being bridled and saddled, pierce your eye without hurting it, especially if you should see mounted on his back such a gallant as St. George, armed with a long sharp lance; or Bellerophon on Pegasus ? And if a thousand eyes should look at one time upon that object, will it not be much lessened, by losing so many atoms and parts, as enter into so many eyes?-Or can the object multiply itself by diminution, as the five loaves did in the gospel?-Or, suppose you should see as many horses at a time as were in Xerxes his army, would there be stable-roon enough in your brain to contain them all?-Or, if you should see a thousand horses, one after another, doth the coming in of the latter drive out the former?-Which way do they come out?-The same way they went in ?-Or some other way?-Or do they stable altogether there?-Or do they die in the brain? --Will they not perish the brain, and poison your optic spirits, with which you say they are mingled?-Or, suppose you should see, in a looking-glass, a horse; doth the atoms of that horse pierce first the glass to get in, and then break through the glass again to get into your eye? Sure, if this be your new philosophy, you are likely to have but few sectaries of these deambulatory wise men, whom you call vulgar philosophers.* Is it not easier, and more consonant to reason, that the image or representation of the object be received into the sense, which reception we call sensation, than to say, that the very material parts which you call atoms, should pierce the organ? for then the same object must be both one and many; and so, if all the inhabitants of either hemisphere should look at once on the moon, there must be as many moons as beholders.

"Again, we distinguish that which you confound, to wit, first, the organ which is called sensorium: secondly, the sensitive faculty, which resides in the spirits: thirdly, the act of sensation, which is caused by the object: fourthly, the object itself which causeth sensation, but not the sense or faculty itself: fifthly, the species which is the image of the object: sixthly, the medium, which is air, water, &c.: seventhly, the sensitive soul, actuating the organ, and in it judging and perceiving the object, which diffuses and sends its species, or spiritual and intentional qualities, both into the medium and the sensorium; and this is no more impossible, than for the wax to receive the impressions or figure of the seal, without any of its matter." ↑

From this precious relic of scholastic subtilty, we learn, first, that the author conceived the species by means of which perception is obtained to be really images or representations of external objects; second, that he conceived these species to be altogether unembodied; third, that the chief ground of difference between him and his opponent consisted in this, that while the one supposed the species to be immaterial, the other fancied them to be composed of atoms which enter by the organs of sense, and "make some motion in the brain." In this respect, Sir Kenelm Digby's hypothesis seems to be merely a revival of the old Epicurean doctrine with respect to the tenuia rerum simulacra; which Lucretius plainly considered as images or resemblances of sensible qualities; perfectly analogous to the species of the peripatetics in every particular but this, that they were supposed to partake of the matter as well as of the form of their respective archetypes.

In the present state of science, when the phraseology of the schoolmen is universally laid aside; and more especially, since the time that the absurdity of their theory of perception has been so fully exposed by Dr. Reid, it is very easy to argue from this absurdity against the probability that the theory was ever matter of general and serious belief. It is easy, for example, to ask what notion it was possible to annex to the words image or representation, when applied to the sensible species, by which we perceive hardness or softness, roughness or smoothness, heat or cold? The question is surely a very pertinent one, and, to all appearance, sufficiently ob

* Compare this with Dr. Beattie's attempts at pleasantry on the very theory which Alexander Ross considered as indisputable.

The Philosophical Touch-stone, or Observations upon Sir Kenelm Digby's Discourses of the Nature of Bodies, and of the Rational Soul. By Alexander Ross, London, 1645.

vious; but it does not therefore follow, that it was ever asked, or that it would have produced much impression, if it had been asked, during the scholastic ages. Such is the influence of words upon the most acute understandings, that when the language of a sect has once acquired a systematical coherence and consistency, the imposing plausibility of the dress in which their doctrines are exhibited, is not only likely to draw a veil, impenetrable to most eyes, over many of the inconsistencies of thought which they may involve, but to give a dexterous advocate infinite advantages in defending and vindicating these inconsistencies, if they should be brought under discussion. When, on the other hand, this technical language has been supplanted by a different phraseology, and when the particular dogmas which it was employed to support come to be examined in separated and unconnected detail, error and absurdity carry along with them the materials of their own refutation; and the mysterious garb, under which they formerly escaped detection, serves only to expose them to additional ridicule. Such has, in fact, been the case with the scholastic theory of perception, which, after maintaining its ground, without any dispute, during a succession of centuries, is now represented as an extravagance of too great a magnitude, to have been ever understood by its abettors in the literal sense which their words convey. It would be happy for science, if some of those who have lately expressed themselves in this matter, did not conceal from superficial readers, and probably from themselves also, under a different, but equally hypothetical form of words, the very same fundamental mistake which revolts their judgment so strongly, when presented to them in terms to which they have not been accustomed.

The theory of Digby, too, when contrasted with that of his antagonist, is a historical document of considerable importance; exhibiting a specimen of the first attacks made on the system of the schoolmen, by the partizans of the new philosophy. The substitution of material images, instead of the ambiguous and mysterious species of Aristotle, by forcing the peripatetics to speak out their meaning a little more explicitly, did more to bring them into discredit, than the most acute and conclusive arguments of their opponents.- -Much about the same time, Dr. Hooke expressed himself not less decidedly about the materiality of ideas or images; employing a mode of speaking on this subject not very unlike that of Dr. Darwin. Priestley's language is somewhat different from this, being faithfully modelled after the hypothesis of his master, Dr. Hartley. "If," says he, "as Hartley supposes, the nerves and brain be a vibrating substance, all sensations and ideas are vibrations in that substance; and all that is properly unknown in the business, is the power of the mind to perceive or be affected with these vibrations." In what manner Dr. Priestley would have reconciled this inference with what I have already quoted from him with respect to the idea of extension, I presume not to conjecture.

As a farther illustration of the notions which were prevalent with respect to the nature of sensible species, and that little more than a century ago, I shall quote a passage from a treatise, which, notwithstanding its unpromising subject, was evidently the work of an author,-deeply tainted, indeed, with the prejudices of his country and of his age, but of no inconsiderable learning and ingenuity. The treatise I allude to is entitled, “ ΔΕΥΤΕΡΟΣΚΟΠΙΑ, or a Brief Discourse concerning the Second Sight, commonly so called. By the Rev. Mr. John Frazer, deceased, late minister of Tirrie and Coll, and Dean of the Isles." (Edinburgh, printed by Mr. Andrew Symson, 1707.)

The passage seems to me to deserve preservation, as a memorial of the state of the Scotish philosophy towards the end of the seventeenth century; and I willingly give it a place here, as the book from which it is extracted is not likely to fall in the way of many of my readers.

After mentioning a variety of anecdotes, concerning the illusions of imagination to which hypochondriacal persons are liable, when in a state of solitude, the author proceeds thus:

"If you will ask, how cometh this to pass? Take notice of the following method, which I humbly offer to your consideration. Advert, in the first place, that visible ideas or species are emitted from every visible object to the organ of the eye, representing the figure and color of the object, and bearing along with it the proportion of the distance; for sure, the objects enter not the eye, nor the interjacent track of ground. And a third thing, different from the eye and the object, and the distant ground, must inform the eye. The species are conveyed to the brain by the optic nerve, and are laid up in the magazine of the memory; otherwise, we should not re

*In consequence of the growing influence of the Cartesian philosophy, these words were then beginning to be regarded as synonymous.

member the object any longer than it is in our presence, and a remembering of those objects is nothing else, but the fancy's receiving, or more properly, the soul of man by the fancy receiving, these intentional species formerly received from the visible object into the organ of the eye, and recondited into the seat of the memory. Now, when the brain is in a serene temper, these species are in their integrity, and keep their rank and file as they were received; but when the brain is filled with gross and flatuous vapours, and the spirits and humours enraged, these ideas are sometimes multiplied, sometimes magnified, sometimes misplaced, sometimes confounded by other species of different objects, &c. &c. and this deception is not only incident to the fancy, but even to the external senses, particularly the seeing and hearing. For the visus, or seeing, is nothing else but the transition of the intentional species through the crystalline humour of the retiform coat of the eye, and judged by the common sense, and conveyed by the optic nerve to the fancy."

"Now, if these species formerly received and laid up in the brain, will be reversed back from the same to the retiform coat and crystalline humor as formerly, there is, in effect, a lively seeing and perception of the object represented by these species, as if de novo the object had been placed before the eye; for the organ of the eye had no more of it before than now it has. Just so with the hearing it is nothing else but the receiving of the audible species to that part of the ear that is accommodated for hearing; so that when the species are retracted from the brain to their proper organs (for example, the ear and the eye), hearing and seeing are perfected, as if the objects had heen present to influence the organ de novo. And it is not to be thought that this is a singular opinion. For Cardanus, an eminent author of great and universal reading and experience, maintains this reversion of the species, and attributes his own vision of trees, wild-beasts, men, cities, and instructed battles, musical and martial instruments, from the fourth to the seventh year of his age, to the species of the objects he had seen formerly, now retracted to the organ of the eye; and cites Averroes, an author of greater renown, for the same opinion." (See Cardanus de subtilitate rerum, p. 301.)

"And it seems truly to be founded upon relevant grounds. I have observed a sick person that complained of great pain and molestation in his head, and particularly of piping and sweet singing in his ears; which seems to have been caused by the species of piping and singing which he had formerly heard; but were now, through the plethory of his head, forced out of the brain to the organ of the ear, through the same nerve by which they were received formerly; and why may not the same befal the visible species as well as the audible? which seems to be confirmed by this optic experiment: Take a sheet of painted paper, and fix it in your window, looking stedfastly to it for a considerable time; then close your eyes very straight, and open your eyes suddenly, you will see the paintings almost as lively as they were in the painted sheet, with the lively colours. This compression of the eyes, by consent causes a compression of the whole brain, which forces back the visible species of the painted sheet to the organ of the eye through the optic nerve, which will presently evanish if the reflectant did not help to preserve them. You may see then how much of these representations may be within ourselves, abstracting from any external agent or object, without the eye to influence the same."

Were it not for the credulity displayed by Mr. Frazer, in various parts of his book, one would almost be tempted to consider the foregoing theory as the effort of a superior mind combating the superstitious prejudices of his age, with such weapons as the erroneous philosophy of that age could supply. Perhaps the spirit of the times did not allow him to carry his scepticism farther than he did. A Lord President of our Supreme Court in Scotland (one of the most eminent and accomplished men whom this country has produced) is said to have been an advocate for this article of popular faith more than fifty years afterwards.

Note (H.) page 90.

In the passage from Locke, quoted in the foot-note, p. 89, a hint is given (very unworthy of his good sense) towards a new theory of the creation of matter. It is a remarkable circumstance, that a theory on the same subject was suggested to Priestley by certain speculations of his own, approaching very nearly to the doctrines of Boscovich; a coincidence which strikes me as a strong additional presumption in favor of that interpretation which I have given to Locke's words.

"I will add in this place, though it will be considered more fully hereafter, that this supposition of matter having (besides extension) no other properties but those

of attraction and repulsion, greatly relieves the difficulty which attends the suppo sition of the creation of it out of nothing, and also the continual moving of it, by a being who has hitherto been supposed to have no common property with it. For, according to this hypothesis, both the creating mind and the created substance, are equally destitude of solidity or impenetrability; so that there can be no difficulty whatever in supposing, that the latter may have been the offspring of the former.” Disquisitions on Matter and Spirit, Vol. I. p. 23. (Birmingham, 1782.)

Note (I.) page 106.

Notwithstanding the apology which I have offered for the word instinct, as it has been sometimes employed by writers on the Human Mind, I am perfectly sensible that it has been used, on various occasions, even by our most profound reasoners, with too great a degree of latitude. Examples of this might be produced, both from Mr. Hume and Mr. Smith; but I shall confine myself, in this note, to a passage from Dr. Reid (by whose phraseology I was led to introduce the subject at present) in which he gives the name of instinct to the sudden effort we make to recover our balance, when in danger of falling; and to certain other instantaneous exertions which we make for our own preservation, in circumstances of unexpected danger.— (See his Essays on the Active Powers of Man, p. 174. 4to edit.)

In this particular instance, I agree perfectly (excepting in one single point) with the following very judicious remarks long ago made by Gravesande :

"Il y a quelque chose d'admirable dans le moyen ordinaire dont les hommes se servent, pour s'empêcher de tomber: car dans le tems que, par quelque mouvement, le poids du corps s'augmente d'un côté, un autre mouvement rétablit l'équilibre dans l'instant. On attribue communément la chose à un instinct naturel, quoiqu'il faille nécessairement l'attribuer à un art perfectionné par l'exercice.

"Les enfans ignorent absolument cet art dans les premières années de leur vie ; ils l'apprennent peu peu, et s'y perfectionnent, parce qu'ils ont continuellement occasion de s'y exercer; exercice qui, dans la suite, n'exige presque plus aucune attention de leur part; tout comme un musicien remue les doigts, suivant les règles de l'art, pendant qu'il apperçoit à peine qu'il y fasse la moindre attention.-(Euvres Philosophiques de M. 's Gravesande, p. 121. Seconde Partie. Amsterdam, 1774.)

The only thing I am disposed to object to in this extract, is that clause where the author ascribes the effort in question to an art. Is it not manifestly as wide of the truth to refer it to this source as to pure instinct?

The word art implies intelligence; the perception of an end, and the choice of means. But where is there any appearance of either, in an operation common to the whole species (not excluding the idiot and the insane);-and which is practised as successfully by the brutes, as by those who are possessed of reason?

I intend to propose some modifications of the usual modes of speaking concerning this class of phenomena, when I come to contrast the faculties of Man with those of the lower animals.

Note (K.) page 109.

Want of room obliges me to omit, at present, the illustrations destined for this note; and to refer to some remarks on secondary qualities, in the Philosophy of the Human Mind. See note (P.) at the end of vol. i.; where I have attempted to explain the reference we make of the sensation of color, to the external object; the only difficulty which the subject seems to me to present, and of which neither Dr. Reid nor Mr. Smith have been sufficiently aware. (See Reid's Inquiry into the Human Mind, and the Essay on the External Senses, in Mr. Smith's Posthumous Work.) Both of these writers have, in my opinion, been led to undervalue this part of the Cartesian Philosophy, by the equivocal use made in the common statements of it, of the names of secondary qualities; a circumstance which had long before been ably commented on by Malebranche.-D'Alembert saw the difficulty in all its extent, when he observed (speaking of the sensation of color): "Rien n'est peut-être plus extraordinaire dans les operations de notre âme, que de la voir transporter hors d'ellemême et étendre, pour ainsi dire, ses sensations sur une substance à laquelle elles ne peuvent appartenir."

Berkeley has made a dexterous and amusing use of this very curious mental phenomenon, to prove that his scheme of idealism was perfectly consonant to the common apprehensions of mankind.

Perhaps, upon a strict inquiry, we shall not find, that even those who from their

birth have grown up in a continued habit of seeing, are irrecoverably prejudiced on the other side, to wit, in thinking what they see to be at a distance from them. For at this time it seems agreed on all hands, by those who have had any thoughts of that matter, that colors, which are the proper and immediate objects of sight, are not without the mind. But then it will be said, by sight we have also the ideas of extension, and figure, and motion; all which may well be thought without, and at some distances from the mind, though color should not. In answer to this, I appeal to any man's experience, whether the visible extension of any object doth not appear as near to him as the color of that object; nay, whether they do not both seem to be in the very same place. Is not the extension we see colored, and is it possible for us, so much as in thought, to separate and abstract color from extension? Now, where the extension is, there surely is the figure, and there the motion too.--I speak of those which are perceived by sight."-(Essay towards a New Theory of Vision, p. 255.)

Note (L.) page 112.

I intended to have introduced here, some doubts and queries with respect to the origin, or rather to the history of the notion of Extension; not with any view to an explanation of a fact which I consider, with the eminent philosophers referred to in the text, as altogether unaccountable; but to direct the attention of my readers to a more accurate examination than has been hitherto attempted, of the occasions on which this notion or idea is at first formed by the mind. Whatever light can be thrown on this very obscure subject may be regarded as a valuable accession to the natural history of the human understanding.

It was long ago remarked by Dr. Reid, (and indeed by other writers of a still earlier date) that to account for the idea of Extension by the motion of the hand, is a paralogism, as this supposes a previous knowledge of the existence of our own bodies.

Condillac does not appear to have been sufficiently aware of this; nor even that most acute and profound philosopher, the late Mr. Smith. In his Essay on the External Senses (published in his posthumous volume), he all along supposes the mind in possession of the idea for the origin of which he is attempting to account. How do we get the notion of what Mr. Smith calls externality, and Berkeley outness? Is not this only a particular modification of the idea of extension?

The same remark may be applied to some late speculations on this subject, by M. Destutt-Tracy. They are evidently the result of great depth and refinement of thought; but, like those of Mr. Smith, they will be found, on an accurate examination, to involve what logicians call a petitio principii.

I am strongly inclined, at the same time, to think, that the idea of extension involves the idea of motion; or to express myself more explicitly, that our first notions of extension are acquired by the effort of moving the hands over the surfaces of bodies, and by the effort of moving our own bodies from place to place. The reference which Smith and Destutt-Tracy, as well as many earlier inquirers have made to the motion of the hand, in their attempts to clear up this mystery, furnishes a strong presumption, that motion is somehow or other concerned in the business. I differ from them only in this: that whereas they seem to have considered their theory as affording some explanation of the origin of the idea, to me it appears, if well-founded, to exhibit this problem in a form still more manifestly insolvable than that in which it is commonly viewed.

From the following query of Berkeley's, it may be inferred what his opinion was on the point in question. Whether it be possible, that we should have had an idea or notion of Extension prior to Motion? Or whether, if a man had never perceived Motion, he would ever have known or conceived one thing to be distant from another?"

To this query I have already said, that I am disposed to reply in the negative; although, in doing so, I would be understood to express myself with the greatest possible diffidence. One observation, however, I may add, without the slightest hesitation, that if the idea of Extension presupposes that of motion, it must, of necessity, presuppose also that of Time.

The prosecution of this last remark has led me into some speculations, which ap pear to myself to be interesting; but to which I find it impossible to give a place in this volume.