not present, and that consequently it cannot be said to perceive external objects themselves, but only their images, forms, or sensible species, which were said to be conveyed through the senses, and represented to the mind in the same manner in which images are formed in a camera obscura. By the internal functions of mind these sensible species were then supposed to be refined into phantasms, the objects of memory and imagination; and these, after undergoing a further process, became intelligible species, the objects of pure intellect.

By a very natural application of this doctrine, it was maintained by bishop Berkeley and the philosophers of his school, that as the mind can perceive nothing but its own impressions or images, we can derive no evidence from our senses of the existence of the external world; and Mr. Hume carried the argument a little further, by maintaining that we have as little proof of the existence of mind, and that nothing exists in the universe except impressions and ideas. Of another sect of philosophers who arose out of the same system, each individual professed to believe his own existence, but would not admit the existence of any other being; hence they received the appropriate name of Egotists.

The various eminent individuals by whom the fallacy of these speculations was exposed, combated them upon the principle that the doctrine of ideas is entirely a fiction of philosophers; and that a confidence in the information con. veyed to us by our senses must be considered as a first truth, or a fundamental law of our nature, susceptible of no explanation, and admitting of no other evidence than that which is derived from the universal conviction of mankind. Nor does it, to common minds, appear a slight indication of the validity of this mode of reasoning, that the philosophers who supported this theory do not appear to have acted upon their own system; but in every thing which concerned their personal accommodation or personal safety, showed the same confidence in the evidence of their senses as other

men.

The deductions made from the ideal theory by Berkeley and Hume seem to have been applications of it which its for

Supposed process by which we become acquainted with external objects. Errors resulting. Berkeley's opinion? Hume's opinion? How refuted. Did these philosophers really believe their own system?

But it is a singular

mer advocates had not contemplated. fact, as stated by Dr. Reid, that nearly all philosophers, from Plato to Mr. Hume, agree in maintaining that the mind does not perceive external things themselves, but only their ideas, images, or species. This doctrine was founded upon the maxim that mind cannot act where it is not present; and we find one writer only, who, admitting the maxim, called in question the application of it so far as to maintain that the mind, in perceiving external things, leaves the body, and comes into contact with the objects of its perception.

Such speculations ought to be entirely banished from the science of mind, as not only useless and unprofitable, but as referring to things entirely beyond the reach of the human faculties, and therefore contrary to the first principles of philosophical investigation. To the same class we are to refer all speculations in regard to the essence of mind, the manner in which thought is produced, and the means by which the intercourse is carried on between the mind and external objects. These remarkable functions were at one time explained by an imaginary essence called the animal spirits, which were supposed to be in constant motion, performing the office of messengers between the brain and the organs of sense. By another class of philosophers, of no very ancient date, thinking was ascribed to vibrations in the particles of the brain. The communication of perceptions from the senses to the mind has been accounted for in the same manner by the motions of the nervous fluid, by vibrations of the nerves, or by a subtile essence, resembling electricity or galvanism. The mind, again, has been com pared to a camera obscura, to a mirror, and to a storehouse. In opposition, however, to all such hypotheses, which are equally incapable either of proof or of refutation, our duty is to keep steadily in view, that the objects of true science are facts alone, and the relations of these facts to each other. The mind can be compared to nothing in nature; it has been endowed by its Creator with a power of perceiving external things; but the manner in which it does so is entirely beyond our comprehension. All attempts, therefore,

Dr Reid's statement? Foundation of this doctrine. Author's opinion of such speculations? Theory of animal spirits. Theory of vibrations. Various other the eries.

to explain or illustrate its operations by a reference to any thing else, can be considered only as vain and futile. They are endeavors to establish a resemblance where there is not a vestige of an analogy; and consequently they can lead to no useful result. It is only by a rigid adherence to this course of investigation that we can expect to make any progress in true knowledge, or to impart to our inquiries in any department of science the characters either of truth or utility.

The ideal theory, with all the doctrines founded upon it, may now be considered as gone by. But certain speculations are still occasionally brought out by writers of a particular order, which are referable to the same class, namely, hypotheses which are to be treated, not merely as unsound, but as being, by their very nature, directly opposed to the first principles of philosophical inquiry. Among these, the most prominent is the doctrine of materialism, of which it may be advisable to take a slight view in the commencement of this essay. On the principles which have been referred to, the following considerations may be submitted as bearing upon the subject.

The term matter is a name which we apply to a certain combination of properties, or to certain substances which are solid, extended, and divisible, and which are known to us only by these properties. The term mind, in the same manner, is a name which we apply to a certain combination of functions, or to a certain power which we feel within, which thinks, and wills, and reasons; and is known to us only by these functions. The former we know only by our senses, the latter only by our consciousness. In regard to their essence or occult qualities, we know quite as little about matter as we do about mind; and in as far as our utmost conception of them extends, we have no ground for believing that they have any thing in common.

It is highly important that the pupil should entertain clear ideas of the distinction between the essence and the properties of bodies. Take, for an example to illustrate this, an orange. It has a peculiar color. This color is one of its properties. Imagine this to be taken away. It has taste, which is another property. Remove this also.

Proper view of the nature of mind? Doctrine of materialism. Reason for alluding to it. Proper applications of the terms matter and mind? Distinction between es sence and properties? Illustration.

It has solidity; that is, it can be felt. Imagine, though it is diffi cult to do so, this property to be removed, so that the hand would pass through it without meeting with any resistance, as if it were a shadow, or an optical deception. Suppose that, in the same way, all other properties are removed, viz. form, smell weight, &c. What would at last be left? Is there an unknown something, around which all these properties cluster? To this something, the term essence is applied. Now all of which we have, or can have any real knowledge, is the vroperties, both in the case of matter and mind.

The true object of philosophy is simply to investigate the facts in regard to both; and materialism is not to be viewed only as unsound reasoning, but as a logical absurdity, and a total misconception of the first principles of philosophical inquiry. Does the materialist tell us that the principle which thinks is material, or the result of organization, we have only to ask him what light he expects to throw upon the subject by such an assertion? For the principle which thinks is known to us only by thinking; and the substances which are solid and extended are known to us only by their solidity and extension. When we say of the former that it is immaterial, we simply express the fact that it is known to us by properties altogether distinct from the properties to which we have given the name of matter, and, as far as we know, has nothing in common with them. Beyond these properties, we know as little about matter as we do about mind; so that materialism is scarcely less extravagant than would be the attempt to explain any phenomenon by referring it to some other altogether distinct and dissimilar; to say, for example, that color is a modification of sound, or gravity a species of fermentation. The assertion, indeed, would be fully as plausible, and calculated to throw as much light upon the subject, were a person anxious to explain the nature of matter, to tell us that it is the result of a particular manifestation of mind. Something analogous to this, in fact, seems to be the foundation of the theory of Boscovich, who conceives all bodies to consist of uncxtended atoms or mathematical points endowed with a certain power of repulsion, and consequently makes the essence of matter to consist merely in the property of resistWe have, in truth, the same kind of evidence for

ance.

True philosophy-what? Its principles violated by materialists-how? Theory of Boscovich. Nature of the evidence of the existence both of matter and mil

the existence of mind that we have for the existence of matter, namely, from its properties; and of the two, the former appears to be the least liable to deception. "Of all the truths we know," says Mr. Stewart, "the existence of mind is the most certain. Even the system of Berkeley concerning the non-existence of matter is far more conceivable than that nothing but matter exists in the universe."

A similar mode of reasoning may be applied to the modification of materialism more prevalent in modern times, by which mind is considered as a result of organization, or, in other words, a function of the brain; and upon which has been founded the conclusion, that, like our bodily senses, it will cease to be when the bodily frame is dissolved. The brain, it is true, is the centre of that influence on which depend sensation and motion. There is a remarkable connection between this organ and the manifestations of mind; and by various diseases of the brain these manifestations are often modified, impaired, or suspended. We shall afterward see that these results are very far from being uniform; but even if they were uniform, the facts would warrant no such conclusion respecting the nature of mind; for they accord equally with the supposition that the brain is the organ of communication between the mind and the external world. When the materialist advances a single step beyond this, he plunges at once into conclusions which are entirely gratuitous and unwarranted. We rest nothing more upon this argument than that these conclusions are unwarranted; but we might go further than this, and contend that the presumption is clearly on the other side, when we consider the broad and obvious distinction which exists between the peculiar phenomena of mind and those functions which are exercised through the means of bodily organization. They do not admit of being brought into comparison, and have nothing in common. The most exquisite of our bodily senses are entirely dependent for their exercise upon impressions from external things. We see not without the presence both of light and a body reflecting it; and if we could suppose light to be annihilated, though the eye were to retain its perfect condition, sight would be ex

Modern materialism? Conrection of the mind with the brain. Dependence of the censes on external objects.