objects, there seems to be some obscurity, and even inconsistency; whether owing to his having had different opinions on the subject at different times, or to the difficulty he found in it, I will not pretend to say.

There are two points in particular, wherein I cannot reconcile him to himself: The first, regarding the place of the ideas or images of external objects, which are the immediate objects of perception; the second, with regard to the veracity of our external senses.

As to the first, he sometimes places the ideas of material objects in the brain, not only when they are perceived, but when they are remembered or imagined; and this has always been held to be the Cartesian doctrine ; yet he sometimes says, that we are not to conceive the images or traces in the brain to be perceived, as if there were eyes in the brain; these traces are only occasions on which, by the laws of the union of soul and body, ideas are excited in the mind; and therefore it is not necessary that there should be an exact resemblance between the traces and the things represented by them, any more than that words or signs should be exactly like the things signified by them.

These two opinions, I think, cannot be reconciled. For, if the images or traces in the brain are perceived, they must be the objects of perception, and not the occasions of it only. On the other hand, if they are only the occasions of our perceiving, they are not perceived at all. Des Cartes seems to have hesitated between the two opinions, or to have passed from the one to the other. Mr. Locke seems, in like manner, to have wavered between the two; sometimes representing the ideas of material things as being in the brain, but more frequently as in the mind itself. Neither Des Cartes nor Mr. Locke could, consistently with themselves, attribute any other qualities to images in the brain, but extension, figure, and motion; for as to those qualities which Mr. Locke distinguished by the name of secondary qualities, both philosophers believed them not to belong to body at all, and therefore could not ascribe them to images in the brain.

Sir Isaac Newton and Dr. Samuel Clarke, uniformly speak of the species or images of material things as being in that part of thebrain called the sensorium, and perceived by the mind there present; but the former speaks of this point only incidentally, and with his usual modesty, in the form of a query. Malebranche is perfectly clear and unambiguous in this matter. According to his system, the images or traces in the brain are not perceived at all; they are only occasions upon which, by the laws of nature, certain sensations are felt by us, and certain of the divine ideas discovered to our minds.

The second point on which Des Cartes seems to waver, is with regard to the credit that is due to the testimony of our senses.

Sometimes, from the perfection of the Deity, and his being no deceiver, he infers, that our senses and our other faculties cannot be fallacious: And since we seem clearly to perceive, that the idea of matter comes to us from things external, which it perfectly resembles, therefore we must conclude, that there really exists something extended in length, breadth, and depth, having all the properties which we clearly perceive to belong to an extended thing.

At other times, we find Des Cartes and his followers making frequent complaints, as all the ancient philosophers did, of the faculties of sense. He warns us to throw off its prejudices, and to attend only, with our intellect, to the ideas implanted there. By this means we may perceive, that the nature of matter does not consist in hardness, colour, weight, or

any of those things that affect our senses, but in this only, that it is something extended in length, breadth, and depth. The senses, he says, are only relative to our present state; they exhibit things only, as they tend to profit or to hurt us, and rarely, and by accident only, as they are in themselves.

It was probably owing to an aversion to admit any thing into philosophy, of which we have not a clear and distinct conception, that Des Cartes was led to deny, that there is any substance of matter, distinct from those qualities of it which we perceive. We say, that matter is something extended, figured, moveable. Extension, figure, mobility, therefore, are not matter, but qualities, belonging to this something, which we call matter. Des Cartes could not relish this obscure something, which is supposed to be the subject or substratum of those qualities; and therefore maintained, that extension is the very essence of matter. But, as we must ascribe extension to space as well as to matter, he found himself under a necessity of holding, that space and matter are the same thing, and differ only in our way of conceiving them; so that, wherever there is space there is matter, and no void left in the universe. The necessary consequence of this is, that the material world has no bounds nor limits. He did not, however, choose to call it infinite, but indefinite.

It was probably owing to the same cause that Des Cartes made the essence of the soul to consist in thought: He would not allow it to be an unknown something that has the power of thinking; it cannot therefore be without thought: And as he conceived that there can be no thought without ideas, the soul must have had ideas in its first formation, which, of consequence, are innate.

The sentiments of those who come after Des Cartes, with regard to the nature of body and mind, have been various. Many have maintained, that body is only a collection of qualities to which we give one name; and that the notion of a subject of inhesion, to which those qualities belong, is only a fiction of the mind. Some have even maintained, that the soul is only a succession of related ideas, without any subject of inhesion. It appears, by what has been said, how far these notions are allied to the Cartesian system.

The triumph of the Cartesian system over that of Aristotle, is one of the most remarkable revolutions in the history of philosophy, and has led me to dwell longer upon it than the present subject perhaps required. The authority of Aristotle was now no more. That reverence for hard words and dark notions, by which men's understanding had been strangled in early years, was turned into contempt, and every thing suspected which was not clearly and distinctly understood. This is the spirit of the Cartesian philosophy, and is a more important acquisition to mankind than any of its particular tenets; and for exerting this spirit so zealously, and spreading it so successfully, Des Cartes deserves immortal honour.

It is to be observed, however, that Des Cartes rejected a part only of the ancient theory, concerning the perception of external objects by the senses, and that he adopted the other part. That theory may be divided into two parts: The first, That images, species, or forms of external objects come from the object, and enter by the avenues of the senses to the mind; the second part is, That the external object itself is not perceived, but only the species or image of it in the mind. The first part Des Cartes and his followers rejected, and refuted by solid arguments; but the second part, neither he nor his followers have thought of calling in question; being persuaded, that it is only a representative image, in the mind, of the ex

ternal object that we perceive, and not the object itself. And this image, which the Peripatetics called a species, he calls an idea, changing the name only, while he admits the thing.

It seems strange, that the great pains which this philosopher took to throw off the prejudices of education, to dismiss all his former opinions, and to assent to nothing, till he found evidence that compelled his assent, should not have led him to doubt of this opinion of the ancient philosophy. It is evidently a philosophical opinion; for the vulgar undoubtedly believe that it is the external object which we immediately perceive, and not a representative image of it only. It is for this reason, that they look upon it as a perfect lunacy to call in question the existence of external objects.

It seems to be admitted as a first principle by the learned and the unlearned, that what is really perceived must exist, and that to perceive what does not exist is impossible. So far the unlearned man and the philosopher agree. The unlearned man says, I perceive the external object, and I perceive it to exist. Nothing can be more absurd than to doubt of it. The Peripatetic says, what I perceive is the very identical form of the object, which came immediately from the object, and makes an impression upon my mind, as a seal does upon wax; and therefore, I can have no doubt of the existence of an object whose form I perceive. But what says the Cartesian? I perceive not, says he, the external object itself. So far he agrees with the Peripatetic, and differs from the unlearned man. But I perceive an image, or form, or idea, in my own mind, or in my brain. I am certain of the existence of the idea, because I immediately perceive it. But how this idea is formed, or what it represents, is not self-evident; and therefore I must find arguments, by which, from the existence of the idea which I perceive, I can infer the existence of an external object which it represents.

As I take this to be a just view of the principles of the unlearned man, of the Peripatetic, and of the Cartesian, so I think they all reason consequentially from their several principles; that the Cartesian has strong grounds to doubt of the existence of external objects; the Peripatetic very little ground of doubt; and the unlearned man none at all: And that the difference of their situation arises from this, that the unlearned man has no hypothesis; the Peripatetic leans upon an hypothesis; and the Cartesian upon one half of that hypothesis.

Des Cartes, according to the spirit of his own philosophy, ought to have doubted of both parts of the Peripatetic hypothesis, or to have given his reasons why he adopted one part, as well as why he rejected the other part; especially since the unlearned, who have the faculty of perceiving objects by their senses in no less perfection than philosophers, and should therefore know, as well as they, what it is they perceive, have been unanimous in this, that the objects they perceive are not ideas in their own minds, but things external. It might have been expected, that a philosopher who was so cautious as not to take his own existence for granted without proof, would not have taken it for granted, without proof, that every thing he perceived was only ideas in his own mind.

But if Des Cartes made a rash step in this, as I apprehend he did, he ought not to bear the blame alone. His successors have still continued in the same track, and, after his example, have adopted one part of the ancient theory, to wit, that the objects we immediately perceive are ideas only. All their systems are built on this foundation.

CHAPTER IX.

THE SENTIMENTS OF MR. LOCKE.

THE reputation which Locke's Essay on human understanding had at home from the beginning, and which it has gradually acquired abroad, is a sufficient testimony of its merit. There is perhaps no book of the metaphysical kind that has been so generally read by those who understand the language, or that is more adapted to teach men to think with precision, and to inspire them with that candour and love of truth, which is the genuine spirit of philosophy. He gave, I believe, the first example in the English language of writing on such abstract subjects with a remarkable degree of simplicity and perspicuity; and in this he has been happily imitated by others that came after him. No author hath more successfully pointed out the danger of ambiguous words, and the importance of having distinct and determinate notions in judging and reasoning. His observations on the various powers of the human understanding, on the use and abuse of words, and on the extent and limits of human knowledge, are drawn from attentive reflection on the operations of his own mind, the true source of all real knowledge on these subjects; and show an uncommon degree of penetration and judgment: But he needs no panegyric of mine; and I mention these things, only that, when I have occasion to differ from him, I may not be thought insensible of the merit of an author whom I highly respect, and to whom I owe my first lights in those studies, as well ás my attachment to them.

He sets out in his essay with a full conviction common to him with other philosophers, that ideas in the mind are the objects of all our thoughts in every operation of the understanding. This leads him to use the word idea so very frequently beyond what was usual in the English language, that he thought it necessary in his introduction to make this apology: "It being that term (says he) which, I think, serves best to stand for whatsoever is the object of understanding, when a man thinks; I have used it to express whatever is meant by phantasm, notion, species, or whatever it is which the mind can be employed about in thinking; and I could not avoid frequently using it. I presume it will be granted me, that there are such ideas in men's minds; every man is conscious of them in himself; and men's words and actions will satisfy him that they are in others."

Speaking of the reality of our knowledge, he says, "It is evident the mind knows not things immediately, but only by the intervention of the ideas it has of them: Our knowledge therefore is real, only so far as there is a conformity between our ideas and the reality of things. But what shall be here the criterion? How shall the mind, when it perceives nothing but its own ideas, know that they agree with things themselves? This, though it seems not to want difficulty, yet I think there be two sorts of ideas that we may be assured agree with things."

We see that Mr. Locke was aware, no less than Des Cartes, that the doctrine of ideas made it necessary, and at the same time difficult, to prove the existence of a material world without us; because the mind, according to that doctrine, perceives nothing but a world of ideas in itself. Not only Des Cartes, but Malebranche, Arnauld, and Norris, had perceived this difficulty, and attempted to remove it with little success. Mr. Locke attempts the same thing; but his arguments are feeble. He even seems

to be conscious of this: For he concludes his reasoning with this observation, "That we have evidence sufficient to direct us in attaining the good and avoiding the evil, caused by external objects, and that this is the important concern we have in being made acquainted with them." This indeed is saying no more than will be granted by those who deny the exist ence of a material world.

As there is no material difference between Locke and Des Cartes with regard to the perception of objects by the senses, there is the less occasion, in this place, to take notice of all their differences in other points. They differed about the origin of our ideas. Des Cartes thought some of them were innate: The other maintained, that there are no innate ideas, and that they are all derived from two sources, to wit, sensation and reflection; meaning by sensation, the operations of our external senses; and by reflection, that attention which we are capable of giving to the operations of our own minds.

They differed with regard to the essence both of matter and of mind: The British philosopher holding, that the real essence of both is beyond the reach of human knowledge; the other conceiving, that the very essence of mind consists in thought; and that of matter in extension; by which he made matter and space not to differ in reality, and no part of space to be void of matter.

Mr. Locke explained, more distinctly than had been done before, the operations of the mind in classing the various objects of thought, and reducing them to genera and species. He was the first, I think, who distinguished in substances what he calls the nominal essence, which is only the notion we form of a genus or species, and which we express by a definition, from the real essence or internal constitution of the thing, which makes it to be what it is. Without this distinction, the subtile disputes which tortured the schoolmen for so many ages, in the controversy between the nominalists and realists, could never be brought to an issue. He shows distinctly how we form abstract and general notions, and the use and necessity of them in reasoning. And as (according to the received principles of philosophers) every notion of our mind must have for its object an idea in the mind itself; he thinks that we form abstract ideas by leaving out of the idea of an individual, every thing wherein it differs from other individuals of the same species or genus; and that this power of forming abstract ideas, is that which chiefly distinguishes us from brute animals, in whom he could see no evidence of any abstract ideas.

Since the time of Des Cartes, philosophers have differed much with regard to the share they ascribe to the mind itself, in the fabrication of those representative beings called ideas, and the manner in which this work is carried on.

Of the authors I have met with, Dr. Robert Hook is the most explicit. He was one of the most ingenious and active members of the Royal Society of London at its first institution; and frequently read lectures to the Society, which were published among his posthumous works. In his lectures upon Light, sect. 7, he makes ideas to be material substances; and thinks that the brain is furnished with a proper kind of matter for fabricating the ideas of each sense. The ideas of sight, he thinks, are formed of a kind of matter resembling the Bononian stone, or some kind of phosphorus; that the ideas of sound are formed of some matter resembling the chords or glasses which take a sound from the vibrations of the air; and so of the rest.

The soul, he thinks, may fabricate some hundreds of those ideas in a day; and that as they are formed, they are pushed farther off from the