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to pretend to perfect divisions, but to leave room for fuch additions or alteracions as a more perfect view of the subject may afterwards suggest.
I fall not, therefore, attempt a complete enumeration of the powers of the human understanding. I shall only mention those which I propose to explain, and they are the following:
ift, The Powers we have by means of our external senses. zdly, Memory. 3dly, Conception. 4thly, The Powers of resolving and analysing complex objects, and compounding those that are more fimple. Sthly, Judging. 6thly, Reafoning. 7thly, Taste. 8thly, Moral perception; and, lat of all, Consciousness.'
To each of the first seven of the intellectual powers contained in the above enumeration, the Author has appropriated a distinct eslay. He has also taken occasion to explain consciousness, the last of them, when giving an account of the first principles of contingent truths, in the estay concerning judgment. But he has not explained the faculty of moral perception in the present work, because, he says, as it is an active as well as an intellectual power, and has an immediate relation to the other active powers of the mind, he apprehends that it is proper to defer the confideration of it till there be explained. We learn from this hint, which occurs at the end of the last essay, that the Doctor proposes to publish another treatise, in which he is to explain the powers of action in the human mind, and in which he will have occasion to explain the principles of morals. Though this important branch of knowledge has employed the abilities of several eminent writers during the present century, yet much light may still be expected from Dr. Reid's accurate judgment, and extensive acquaintance with the powers of human nature.
Those essays which are presented to the Public in this volume may be considered as finished productions of long and laborious ftudy. They contain the substance of lectures which were delivered annually, first in the university of Aberdeen, and afterwards in that of Glasgow, for the space of thirty years, during which time they have been the objects of the Author's particuJar attention, and have, of coniequence, undergone frequent and careful revisals. The reader, therefore, has no reason to expect any crude and random effusions of a brilliant fancy, nor any thing that has not undergone the scrutiny of mature judge ment and reflection : and when, added to this, he takes into confideration the eminent abilities and discernment of the Author, he may see cause for suspending his decision, though cases should occur, in which he is inclined to differ from him in opipion. The doctrines of many philosophers, whose names stand highest in this department of literature, are examined by the Author with freedom, and the foundation on which they are built is frequently attacked. But the weapon which he employs against them iş manly reasoning, free from that captious fophiftry which so frequently disgraces metaphysical writings, and not 3
polluted by the illiberality and petulance which so frequently occur in the discussion of controversial matters. He generally Races opinions and arguments in the words of those who have publ thed them, and though he deduces those consequences which he thinks fairly follow them, yet he does not impute to the authors of the premises any of the conclusions which they themselves have not drawn and avowed. Hence he candidly exempts from all suspicion of scepticism, several of those writers whole principles seem to lead directly to that indecisive and comfortless sort of speculation.
The first of these essays is preliminary, and consists of eight chapters. In imitation of the mathematicians, who have excluded wrangling and idle disputes from the sciences that respect quanuity and number, by defining, accurately the terms which they have occasion to use, Dr. Reid devores the first chapter of this essay to the explication of certain words, that frequently occur in the language of those philosophers who have treated of the human understanding. The terms which he has particularly explained, in this chapter, are mind, operations of mind, power and faculty, things in the mind and things external to the mind, thinking, perception, consciousness, conceiving, imagining and apprehending, object of perception, idea, impresion, and sensation. He observes, that no proper logical dennition of such terms can be given; but the meaning of them may, however, be ascertained so as to prevent all ambiguity and mistake in the application of them. He places in a very striking light the importance of such explications, by pointing out the manner in which some of these words have been abused by philosophical writers, perverted from their usual meaning, and applied sometimes in one fignification and soinetimes in another, with a view to present in a favourable light certain peculiar tenets. We Thall infert, as a specimen, the explication of the terms perception and sensation. We are the more disposed to select there, because inatiention to the distinction between the operations of mind. which they denote, appears to have been the principal occasion of certain paradoxical opinions, with regard to the existence both of matter and of spirit, embraced by some modern philosophers.
• First, We are never said to perceive things, of the existence of which we have not a full conviction. I may conceive or imagine a mountain of gold, or a winged horse; but no man says that he perceives such a creature of imagination. Thus perception is distinguished from conception or imagination. Secondly, Perceprion is applied only to external objects, not to those that are in the mind itself. When I am pained, I do not say that I perceive pain, but that I feel it, or that I am conscious of it. Thus perception is distinguished from confciousness. Thirdly, The immediate object of perception must be something present, and not what is past. We may remember what is paft, but do not perceive it. I may fay, I perceive such a perfon
has had the small-pox; but this phrase is figurative, although the figure is so familiar that it is not observed. The meaning of it is, that I perceive the pits in his face, which are certain signs of his having had the small-pox. We say we perceive the thing signified, when we only perceive the sign. But when the word perception is used properly, and without any figure, it is never applied to things paft. And thus it is distinguished from remembrance.
• In a word, perception is most properly applied to the evidence we have of external objects by our senses. But as this is a very clear and cogent kind of evidence, the word is often applied by analogy to the evidence of reason, or of testimony, when it is clear and cogent. The perceprion of external objects by our senses, is an operation of the mind of a peculiar nature, and ought to have a name appropriated to it. It has so in all languages. And, in English, I know no word more proper to express this act of the mind ihan perception. Seeing, hearing, smelling, tafting, and touching or feeling, are words that express the operations proper to each sense ; perceiving exprefles that which is common to them all.
• The observations made on this word would have been unnecessary, if it had not been so much abused in philosophical writings upon the mind; for in other writings it has no obfcurity. Although this abuse is not chargeable on Mr. Hume only, yet I think he bas carried it to the highest pitch. The first sentence of his treacise of hu. man nature runs thus: “ All the perceptions of the human mind resolve themselves into two diftin&t heads, which I shall call impreffions and ideas.” He adds, a little after, that under the name of impressions, he comprehends all our sensations, paffions, and emotions. Here we learn that our passions and emotions are perceptions. I believe no English writer before him ever gave the name of a per. ception to any paflion or emotion. When a man is angry, we must say that he has the perception of anger; when he is in love, that he has the perception of love. He speaks often of the perceptions of memory, and of the perceptions of imagination; and he might as well speak of the hearing of light, or of the smelling of touch : for, surely, hearing is not more different from fight, or smelling from touch, than perceiving is from remembering or imagining.'
Sensation is a name given by philosophers to an act of mind, which may be distinguished from all others by this, that it hath no object distinct from the act itself. Pain of every kind is an uneasy sensation. When I am pained, I cannot say that the pain I feel is one thing, and that my feeling it is another thing. They are one and the lame thing, and cannot be disjoined, even in imagination. Pain, when it is not felt, has no existenee. It can be neither greater nor less in degree or duration, nor any thing else in kind, than it is felt to be. It cannot exist by itself, nor in any subject, but in a sentient being. No quality of an inanimate insentient being can have the least resemblance to it.
• What we have said of pain may be applied to every other sensation. Some of them are agreeable, others uneasy, in various degrees. These being objects of desire or averfion, have some attention given to them, but many are indifferent, and so little attended 10, that they have no name in any language.
· Most operations of the mind, that have no names in common language, are complex in their nature, and made up of various ingredients, or more simple acts; which, though conjoined in our con, fitution, must be disjoined by abstraction, in order to our having a diftin&t and scientific notion of the complex operation. In such operations, sensation for the moit part makes an ingredient. Those who do not attend to the complex nature of such operations, are apt to resolve them into some one of the simple acts of which they are compounded, overlooking the others : and from this cause many disputes have been raised, and many errors bave been occasioned with regard to the nature of luch operations.
• The perception of external objects is accompanied with some sensation corresponding to the object perceived, and such sensations have, in many cases, in all languages, the same name with the ex. ternal object which they always accompany. The difficulty of dir, joining, by abstraction, things thus constantly conjoined in the course of nature, and things which have one and the same name in all languages, has likewise been frequently an occasion of errors in the phie losophy of the mind. To avoid fuch errors, nothing is of more importance than to have a distinct notion of that simple act of the mind which we calt sensation, and which we have endeavoured to describe. By this means we shall find it more easy to distinguish it from every external object that it accompanies, and from every other act of the mind that may be conjoined with it. For this purpose, it is likewise of importance, that the name of sensation should, in philofophical writings, be appropriated to signify this simple act of the mind, without including any thing more in its signification, or being applied to other purposes.
• I Mall add an observation concerning the word feeling. This word has two meanings. First, it fignifies the perceptions we have of external objects, by the sense of rouch. When we speak of feel ing a body to be hard or soft, rough or smooth, hot or cold; to feel these things is to perceive them by touch. They are external things, and that act of the mind by which we feel them, is easily distinguished from the objects felt. Secondly, the word feeling is used to signify the same thing as sensation, which we have just now explained ; and, in this sense, it has no obje&t'; the feeling and the thing felt are one and the fame.
• Perhaps betwixt feeling, taken in this last sense, and sensation," there may be this small difference, that sensation is most commonly used to signify those feelings which we have by our external senses and bodily appetites, and all our bodily pains and pleasures. But there are feelings of a nobler nature accompanying our affections, our moral judgments, our determinations in matters of taste, to which the word sensation is less properly applied.'
In the second chapter of the preliminary essay, Dr. R. mentions certain principles which he takes for granted, as being self-evident, and needing no proof. In this particular, as well as in the explication of his terms, he very judiciously follows the laudable practice of the mathematicians, which was introduced into natural philosophy by Sir Isaac Newton, and has
been produ&tive of much benefit in that branch of science, He thinks, very justly, that there is as much occasion for laying down first principles in the philosophy of mind as in other branches of human knowledge, because some ingenious men have fallen into inconclufive reasoning from endeavouring to prove certain truths, which being self-evident do not admit of proof. Descartes thought it neceffary to prove his own exiltence; others have attemped to prove that those external things exist which are perceived by the Renfes. Sceptical writers found it no difficult talk to overturn the arguments upon which these philosophers had founded their conclufions, and improving the advantage they had gained, as if the truths themselves had been supported by no lurer evidence than that which had been unneceffarily produced, denied that either the things perceived, or the percipient being, have any existence. Dr. Reid being no advocate for blind credulity, lays it down as a maxim, that' ought to be cautious that we do not adopt opinions as first principles, which are not entitled to that character. The only principles, accordingly, which he takes for granted, are selfevidene truths, of the belief of which no man in his fenles can seriouly divest himself, though some of them have been doubled of, or denied, by a few speculative persons in their ftudious hours.
It is natural for men, when things occur in the course of their inquiries which they do not fully comprehend, to indulge themselves in forming guefles and conjectures concerning them, and after contriving a plaufible theory, they are apt to fubftitute it in the place of knowledge, and to rely upon che fabric which bas been erected by their own imaginations, as if it were a solid building. Men are also inclined to form opinions concerning matters which they have never examined, by suppofing that they have a resemblance to other matters with which they are better acquainted. If we proceed in our researches after truth in either of these ways, the probability is that we hall be deceived. It is sot likely that our conjectures will correspond with the nature of things, or that the properties of things very different from one another are the same. Many of those, however, who have treated of the mind have had recourse to conjecture, with a view to explain facts, or have reasoned on the supposition that there is jomething in mind fimilar to body, so that the powers and operations of the former may be explained and understood by means of an acquaintance with the latter. In opposition to these unphilosophical modes of proceeding, Dr. Reid, in the two lublequent chapters, treats, first, of hypotheses, or conjectures, to which he ihinks no regard whatever is due in the investigation of truth, and which ought of consequence to be banished from fcience; and, secondly, of analogy, which, though ufeful in some