smallest degree, be affected, although the truth of any one of them should be fully established. It is not, therefore, on account of its inconsistency with any favourite opinions of my own, that I would oppose the disquisitions either of scholastic pneumatology, or of physiological metaphysics; but because I consider them as an idle waste of time and genius on questions where our conclusions can neither be verified nor overturned by an appeal to experiment or observation. Sir Isaac Newton's query concerning the cause of gravitation was certainly not inconsistent with his own discoveries concerning its laws; but what would have been the consequences to the world, if he had indulged himself in the prosecution of hypothetical theories with respect to the former, instead of directing his astonishing powers to an investigation of the latter?

That the general spirit of Dr Reid's Philosophy is hostile to the conclusions of the Materialist, is indeed a fact: Not, however, because his system rests on the contrary hypothesis as a fundamental principle, but because his inquiries have a powerful tendency to wean the understanding gradually from those obstinate associations and prejudices, to which the common mechanical theories of mind owe all their plausibility. It is, in truth, much more from such examples of sound research concerning the Laws of Thought, than from any direct metaphysical refutation, that a change is to be ex

pected in the opinions of those who have been accustomed to confound together two classes of phenomena, so completely and essentially different.-But this view of the subject does not belong to the present argument.

It has been recommended of late, by a medical author of great reputation, to those who wish to study the human mind, to begin with preparing themselves for the task by the study of anatomy. I must confess, I cannot perceive the advantages of this order of investigation; as the anatomy of the body does not seem to me more likely to throw light on the philosophy of the mind, than an analysis of the mind to throw light on the physiology of the body. To ascertain, indeed, the general laws of their connexion from facts established by observation or experiment, is a reasonable and most interesting object of philosophical curiosity; and in this inquiry (which was long ago proposed and recommended by Lord Bacon), a knowledge of the constitution both of mind and body is indispensably requisite; but even here, if we wish to proceed on firm ground, the two classes of facts must be kept completely distinct; so that neither of them may be warped or distorted, in consequence of theories suggested by their supposed relations or analogies *. Thus, in many of the phenomena, connected with Custom and Ha

Elements of the Philosophy of the Human Mind, pp. 11, 12. 2d edit.

bit, there is ample scope for investigating general laws, both with respect to our mental and our corporeal frame; but what light do we derive from such information concerning this part of our constitution as is contained in the following sentence of Locke? "Habits seem to be but trains of mo“tion in the animal spirits, which, once set a-going, conti"nue in the same steps they had been used to, which by of"ten treading arc worn into a smooth path." In like manner, the laws which regulate the connexion between the mind and our external organs, in the case of Perception, have furnished a very fertile subject of examination to some of the best of our modern philosophers; but how impotent does the genius of Newton itself appear, when it attempts to shoot the gulf which separates the sensible world, and the sentient principle? "Is not the sensorium of animals," he asks in one of his queries, "the place where the sentient "substance is present, and to which the sensible species of things are brought through the nerves and brain, that they may be perceived by the mind present in that place?"

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It ought to be remembered also, that this inquiry, with respect to the laws regulating the connexion between our bodily organization, and the phenomena subjected to our own consciousness, is but one particular department of the philosophy of the mind; and that there still remains a wide and indeed boundless region, where all our data must be obtain

ed from our own mental operations. In examining, for instance, the powers of judgment and reasoning, let any person of sound understanding, after perusing the observations of Bacon on the different classes of our prejudices, or those of Locke on the abuse of words, turn his attention to the speculations of some of our contemporary theorists; and he will at once perceive the distinction between the two modes of investigation which I wish at present to contrast. Rea"soning," says one of the most ingenious, and original of these," is that operation of the sensorium, by which we ex"cite two or many tribes of ideas; and then re-excite the ideas, in which they differ or correspond. If we deter"mine this difference, it is called Judgment; if we in vain "endeavour to determine it, it is called Doubting.—If we "re-excite the ideas in which they differ, it is called Distin

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guishing; if we re excite those in which they correspond, "it is called Comparing *."-In what acceptation the word idea is to be understood in the foregoing passage, may be learned from the following definition of the same author :— "The word idea has various meanings in the writers of metaphysic: It is here used simply for those notions of ex"ternal things, which our organs of sense bring us acquaint"ed with originally; and is defined, a contraction, or mo"tion, or configuration, of the fibres, which constitute the

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Zoonomia, vol. i. p. 181. 3d edit,

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"immediate organ of sense *."-Mr Hume, who was less of a physiologist than Dr Darwin, has made use of a language by no means so theoretical and arbitrary; but still widely removed from the simplicity and precision essentially necessary in studies, where every thing depends on the cautious use of terms. Belief," according to him, is " a lively "idea related to or associated with a present impression; Memory is the faculty by which we repeat our impressions, so as that they retain a considerable degree of their "first vivacity, and are somewhat intermediate betwixt an "idea and an impression."

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According to the views of Dr Reid, the terms which express the simple powers of the mind, are considered as unsusceptible of definition or explanation; the words, Feeling, for example, Knowledge, Will, Doubt, Belief, being, in this respect, on the same footing with the words, Green or Scarlet, Sweet or Bitter. To the names of these mental operations, all men annex some notions, more or less distinct ; and the only way of conveying to them notions more correct, is by teaching them to exercise their own powers of reflection. The definitions quoted from Hume and Darwin, even if they were more unexceptionable in point of phraseology, would, for these reasons, be unphilosophical, as at

• Zoonomia, vol. i. pp. 11, 12.