labour has uniformly ended in a sentiment of regret, at the time and attention which I had misemployed in so hopeless and so ungrateful a task.

Mr. Locke, although he occasionally indulges himself in hints and conjectures, somewhat analogous to those of Hartley and Darwin, seems to have been perfectly aware how foreign such speculations are to the genuine Philosophy of the Human Mind. The following are his own words, in the second paragraph of the Introduction to his Essay:-"This, therefore, being my purpose, to in'quire into the original, certainty, and extent of human 'knowledge; together with the grounds and degrees of "belief, opinion, and assent, I shall not, at present, med"dle with the physical consideration of the mind, or "trouble myself to examine, wherein its essence con"sists, or by what motions of our spirits, or alteration of 66 our bodies, we come to have any sensation by our or'gans, or any ideas of our understandings; and whether "these ideas do in their formation, any or all of them,

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depend on matter or not. These are speculations, "which, however curious and entertaining, I shall de"cline, as lying out of my way in the design I am now "upon." It is much to be wished, that Mr. Locke had adhered invariably to this wise resolution.

I flatter myself it will not be inferred, from the manner in which I have expressed myself with respect to the common theories of physiologists about the causes of the intellectual phenomena, that I entertain any doubt of the intimate connection which exists between these phenomena and the organization of the body. The great principle which I am anxious to inculate, is, that all the theories which have yet been offered on this subject, are entirely

unsupported by proof; and what is worse, are of such à kind, that it is neither possible to confirm nor to refute them, by an appeal to experiment or observation. That I was all along fully aware of the dependence, in our present state, of our mental operations on the sound condition of our corporeal frame, appears sufficiently from what I remarked, many years ago, concerning the laws of this connection between mind and body, as presenting one of the most interesting objects of examination connected with the theory of human nature.*

I have been induced to caution my Readers against the possibility of such a misapprehension of my meaning, by the following passage in a late publication: "What that "affection of the brain is," (says Mr Belsham) "which, "by the constitution of human nature, causes Memory, "we cannot absolutely ascertain. The hypothesis of Vi. "brations, which has already been explained, is the most probable. It is trifling to object, that if the existence of impressions on the brain could be proved, Memory "would remain as unaccountable as before: all which "this hypothesis pretends to, is to advance a step in tra

cing the process of the connection between external obแ 'jects and mental feelings."" It is curious to observe," (the same author continues) "that Dr. Reid, after start"ing several objections against the commonly received "hypotheses, is obliged to admit, that many well-known "facts lead us to conclude, that a certain constitution or "state of the brain is necessary to Memory."

On this passage I shall offer only two remaks. The first is, that, notwithstanding Mr. Belsham's zeal for Hartley's

* Philosophy of the Human Mind, pp. 11, 12, 3d ed.

Theory of Vibrations, he confesses explicitly, that "we "cannot absolutely ascertain, what that affection of the "brain is, which, by the constitution of human nature, "causes memory;" and that, "the theory of Vibrations, though more probable than some others, is still but an hypothesis." Secondly, that Mr. Belsham, after making this explicit acknowledgment, is nevertheless pleased to insinuate, that all who presume to object to this particular hypothesis, are bound by their own principles to assert, that memory has no dependence whatever on the state of the brain. Where the inconsistency lies in Dr. Reid's admission, that a certain constitution or state of the brain is necessary to memory, after he had stated some objections against the commonly received theories, I am at a loss to discover. Indeed, I should be glad to know, what philosopher, ancient or modern, has ever yet asserted, that memory is not liable to be injured by such affections of the brain as are produced by intemperance, disease, old age, and other circumstances which disturb the bodily mechanism. The philosophical inference, however, from this concession is, not that the hypothesis of Dr. Hartley, or the hypothesis of Mr. Belsham must necessarily be true; but that, laying aside all hypotheses, we should apply ourselves to collect such facts as may lead us, in due time, to the only satisfactory conclusions we have much chance of ever forming concerning the connection between mind and body-the discovery of some of the general laws by which this connection is regulated.

In offering these strictures on the physiological metaphysics of the present day, it is proper for me, at the same time, to observe, that I object to it merely as an idle waste of labour and ingenuity, on questions to which the human

faculties are altogether incompetent; and not because I consider any of the theories, to which it has given birth, as standing in the way of my own doctrines. The facts which I wish to ascertain rest on their own proper evidence; an evidence which would remain entire and unshaken, although a demonstration should be produced in favour of the animal spirits of Des Cartes, or of the Vibrations of Hartley; and which would not gain the slightest accession of strength, if both these hypotheses were to fall into the contempt they deserve. The circumstance which peculiarly characterizes the inductive Science of the Mind is, that it professes to abstain from all speculations concerning its nature and essence; confining the attention entirely to phenomena, which every individual has it in his power to examine for himself, who chooses to exercise the powers of his understanding. In this respect, it differs equally in its scope, from the pneumatological discussions concerning the seat of the Soul, and the possibility or the impossibility of its bearing any relation to Space or to Time, which so long gave employment to the subtility of the schoolmen;-and from the physiological hypotheses which have made so much noise at a later period, concerning the mechanical causes on which its operations depend. Compared with the first, it differs, as the inquiries of Galileo concerning the laws of moving bodies differ from the disputes of the ancient sophists concerning the existence and the nature of motion. Compared with the other, the difference is analogous to what exists between the conclusions of Newton about the law of gravitation, and his query concerning the invisible ether, of which he supposed it might possibly be the effect.-It may be worth while to add, in passing, that the diversity of opinion among New

ton's followers, with respect to the verisimilitude of this query, while they have unanimously acquiesced in the physical conclusions of their master, affords an instructive proof, how little the researches of inductive science are liable to be influenced by the wanderings of Imagination, in those regions which human reason is not permitted to explore. Whatever our opinion concerning the unknown physical or metaphysical cause of gravitation may be, our reasonings concerning the system of nature will be equally just, provided only we admit the general fact, that bodies tend to approach each other with a force varying with their mutual distances, according to a certain law. The case is precisely similar with respect to those conclusions concerning the mind, to which we are fairly led by the method of Induction. They rest upon a firm and indisputable basis of their own; and (as I have elsewhere remarked) are equally compatible with the metaphysical creeds of the Materialist and of the Berkeleian. *

The hypothesis which assumes the existence of a subtle fluid in the nerves, propagated by their means from the brain to the different parts of the body, is of great antiquity; and is certainly less repugnant to the general analogy of our frame, than that by which it has been supplanted. How very generally it once prevailed, may be inferred from the adoption into common speech of the phrase anima! spirits, to denote that unknown cause which "gives vigour or cheerfulness to the mind;”—a phrase for which our language does not, at this day, afford a convenient substitute. The late Dr. Alexander Monro (one of the most cautious and judicious of medical inquirers) speaks of it as a fact which appeared to him to be almost indisputable. "The "existence of a liquid in the cavities of the nerves, is supported by "little short of demonstrative evidence." (See some observations of his, published by Cheselden in his Anatomy.)

The hypothesis of Vibrations first attracted public notice in the writings of Dr. William Briggs. It was from him that Sir Isaac Newton derived his anatomical knowledge; along with which he ap