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nished us with no materials of thought but sensations, his conclufion must be just; for no sensation can give us the conception of material things, far less any argument to prove their exiftence. But if it is true that by our senses we have not only a variety of sensations, but likewise a conception, and an imme. diate natural conviction of external objects, he reasons from a false fuppofition, and his arguments fall to the ground.'
Having, in the preceding part of the Effay, fully considered the powers of perception and sensation, Dr. Reid proceeds in the seventeenth and eighteenth chapters to treat of those objects which are perceived, chiefly to explain the notions which our senses give us of them. The objects of perception are the various qualities of bodies. Dr. Reid admits, with Mr. Locke, the reality of the diftinction between primary and secondary qualities, though it has been rejected by Bishop Berkeley and Mr. Hume, and ascertains the difference between them to be, that our senses give us a direct and a distinct notion of the primary qualities, and inform us what they are in themselves : but of the secondary qualities our senses give us only a relative and obfcure notion.'' To explain his meaning more clearly, he observes, that a relative notion is, strictly speaking, no notion of the tbing at all, but only of some relation which it bears to something else. I have a direct and diftin&t notion of gravity when I conceive it to be the tendency of bodies toward the earth. But the term gravity is sometimes applied to the unknown cause of this tendency. Whenever this cause is the object of thought, our notions of it give us no conception of the thing itself, but only of the relation it bears to its effect. In like manner the quality of a rose, which is called its smell, is an unknown quality ; but it bears a relation to a sensation excited in me of which it is the cause or occasion, and therefore the notion I bave of it is only relative, and not direct. My senses give me no information of the quality itself, but only of its relation to something else. Neither primary nor secondary qualities relemble any sensation; but of the primary qualities we have diftin&t notions, and we can reason concerning them with precision. Of the secondary qualities we have no such distinct notions; and as their nature is not obvious to sense, it may be the object of dispute, though it is a proper subject of philosophical disquisition, and some progress has been made in it. These observations certainly throw much new light upon this important diftin&ion, The following reflection is as curious as it is evident, and we are surprised that it did not readily occur to every person who thought on the subject :
We may see why the sensations belonging to fecondary qualities are an object of our attention, while those which belong to the primary are not.
· The firft are not only signs of the obje&t perceived, but they bear a capital part in the notion we form of it. We conceive it only as that which occasions such a sensation, and therefore cannot reflect upon it without thinking of the sensation which it occasions : we have no other mark whereby to distinguish it. The thought of a secondary quality, therefore, always carries us back to the sensations which it produces. We give the same name to both, and are apt to confound them together.
• But having a clear and distinct conception of primary qualities, we have no need when we think of them to recal their sensations. When a primary quality is perceived, the sensation immediately leads our thoughts to the quality fignified by it, and is itself forgot. We have no occasion afterwards to reflect upon it; and so we come to be as little acquainted with it as if we had never felt it. This is the case with the sensations of all primary qualities, when they are not so painful or pleasant as to draw our attention.
• When a man moves his hand rudely against a pointed hard body, he feels pain, and may easily be persuaded that this pain is a sensation, and that there is nothing resembling it in the hard body; at the same time he perceives the body to be hard and pointed, and he knows that these qualities belong to the body only. In this case it is easy to distinguish what he feels from what he perceives.
• Let him again touch the pointed body gently, so as to give him no pain, and now you can hardly persuade him that he feels any thing but the figure and hardness of the body; so difficult it is to at. tend to the sentations belonging to primary qualities, when they are neither pleasant nor painful. They carry the thought to the exter. nal object, and immediately disappear and are forgot. Nature intended them only as figns; and when they have served that purpose they vanish."
Affuming these observations as well founded, Dr. Reid next points out the miftakes that have prevailed upon this subject.
• Besides primary and secondary qualities of body,' says our Author in continuation, there are many other immediate objects of perception. Without pretending to a complete enumeration, I think They mostly fall under one or other of the following claffes. ift. Certain states or conditions of our bodies. 2d. Mechanical powers or forces. 3d. Chemical powers. 4th. Medical powers or virtues. 5th. Vegetable or animal powers. He shews that our notions of all these qualities are obscure and relative, and that they are therefore analogous to our notions of secondary qualities. Our senses difcover the effect; but the power is latent. We know there must be a cause of the effect, and we form a relative notion of it from its ef. feet ; and very often the same name is used to signify the unknown cause, and the known effect.'
In the nineteenth chapter Dr. Reid treats of matter and of space. The things immediately perceived by our senses are qualities. But we have a natural conviction that sensible qualities cannot exist by themselves without some subject to which they belang, and which is called matter, or body. All men accord. ingly ascribe qualities to come subject ; and what one man accounts à quality, all men do, and ever did. Our senses give us no information about matter, but that it is the subject to which fenfible qualities belong. Our notion of it is, therefore, obfcure and relative. It can, however, easily be distinguished from all other relations; as from the relation of an effeèt to its cause, or of a fign from the thing signified. The existence, motion, and relative situations of matter suppose space. Space is nor perceived by any of our senses ; but the notion of it is a neceffary concomitant, whenever we form a conception of the primary qualities, and being once introduced by the proper objects of touch and fight, it remains in our conception and belief, though the objects which introduced it be removed, and fwells to immensity without any limiis either of extent or dura. tion. Dr. Reid admits Bishop Berkeley's distinction between tangible and visible space, or real and apparent figure and magnitude, arising from the different appearance of the same object, as the conception of it has been formed by the fight aided by the touch, or by the fight alone. While he admits the distinction, however, as well founded, he controverts the Bishop's doctrine built upon it, that visible and tangible magnitude and figure are things totally different and diffimilar, and cannot both belong to the same object.
In the twentieth chapter he treats of the evidence of fenre, or the grounds on which we believe the existence of those things which we perceive. This belief be considers as the effe&t of our conftitution, and unaccountable. He also compares the evidence of sense with various other kinds of evidence, and points out the particulars in which it agrees with them, or differs from them.
In the twenty-first chapter of this Essay the Author treats' of the improvement of the senses by habit, by due care of their organs, by attention to objects, by artificial organs or inftruments, and by discovering the connection which nature has established between the sensible qualities of objects and their more latent qualities.
The last chapter contains a most ingenious and satisfactory differtation concerning the fallacy that has often been imputed to the senses. Philosophers in all ages have complained that the senses deceive us. This complaint the Author clearly shews to be ill founded. We owe to our external senfes (wo powers, sensation and perception. In sensation there can be no fallacy. It can neither be greater nor less than we feel it. Our power of perception is limited, and is liable to be hurt, or even destroyed, by disorders of the body, but is not fallacious. The appearances commonly imputed to the fallacy of the senses are reduced by the Author to four classes. First, Some of them are conclusions ralhly drawn from the testimony of the senses. If a man cakes a counterfeit guinea for a true one, it is not his renses that deceive him, but a rash judgment, occasioned by a reliance upon some properties discovered by the senses, and neglect of other properties which the senses could also have dir. covered if they had been properly consulted. We often mistake relative motion for real motion ; but by our senses we perceive only relative motion, and from it by reasoning we infer the real. Secondly, Some of these errors are those we are liable to in our acquired perceptions, which are conclusions drawn in the course of experience from what the senses testify, When I see a globe, I perceive that it is a solid figure; but this perception is not the teftimony of my sense of feeing. I see only a circular form with the light and colour distributed over it in a certain way; but having been accustomed to observe this diftribution only in a spherical body, I believe the object co be spherical, and say I see it to be such. A painter by imitating that distribution of light and colour may deceive me, but the error arifes from the conclusion 1 form, and not from any false report made by the sight. Thirdly, Some of these errors arise from ignorance of the laws of nature. We learn by experience to judge from the sound on what side the founding body is placed, but we may be deceived by an echo that returns the found. A child believes that its own image in the mirror is another child, from unacquaintance with the reflection of the Fays of light. Such appearances give just and true information to those who are acquainted with the laws of nature, and arise from no fallacy whatever in the senses. The last class of errors, and the only one in which there is any deception, proceed from fome disorder or preternatural ftate of the organs of perception, All the human faculties are liable to be hure by accidental causes, and unfitted for their natural functions. These oblero vations are illustrated in a full and perspicuous manner.
• Upon the whole,' fays the Author, it seems to have been a cominon error of philosophers to account the lenses fallacious. And to this error they have added another, that one use of reason is to detect the fallacies of rense.
• It appears, I think, from what has been said, that there is no more reason to account our senses fallacious, than our reason, our memory, or any other faculty of judging which nature hath given
They are all limited and imperfect, but wisely suited to the present condition of man. We are liable to error and wrong judg; ment in the use of them all; but as little in the informations of sense as in the deductions of reasoning. And the errors we fall into with regard to the objects of sense are not corrected by reason, but by more accurate attention to the informations we may receive by our feases themselves.'
We consider this learned and ingenious Eslay as a valuable addition to the knowledge of the human understanding; and the principles establidhed in it evidently lead to many important conclusions with regard to the nature of man.
(To be concluded in our next.) A. ART. II, Memoirs of the Literary and Philosophical Society of Manchef
ter, continued : See Review for May, 1786.
MisceLLANEOUS PAPER S. Remarks on the different Success, with respect to Health, of some At
tempts to pass the Winter in high northern Latitudes. By John Aikin, M. D. N the beginning of the la£ century several voyages of disco
very were made in the northern seas; and the Greenland wbale fishery began to be pursued with vigour by various European nations. These two circumstances gave rise to several inAances of accidental wintering in the dreary and desolated lands of high northern latitude. The very different success attending thefe attempts bas attracted the peculiar attention of Dr. Aikin; who has, in this paper, given an abftract of the journals of the different companies who have wintered in Greenland and its neighbourhood ; with observations on their diet, mode of living, and diseases. He concludes with a comparison of their several circumftances, and some remarks on the general result. The fcurvy appears to be the disease peculiarly fatal in all the ato tempts that have been made to winter in these inhospitable climates; but whether the cold itself, or the want of proper food, occafioned by it, principally conduces to the generation of the disease, is a matter not clearly ascertained. On comparing the histories of different people who have wintered there, the Doctor obferves, that those in whom the scurvy raged fed upon falt provisions, and drank spirituous liquors; whereas those who escaped it, fed upon fresh animal food, or, at least, that which was preserved without falt; and drank water. There facts lead to the contideration of the question, Whether salted meat be prejudicial on account of the quantity of salt it contains, or merely because the sale fails to preserve the juices of the flela in such a fate as to afford proper nourishment? After reasoning on the subject, the Doctor finally concludes with the opinion, " that the use of fea-falt is a very principal cause of the scurvy; and that a total abstinence from it is one of the molt important means for preventing this disease.'
Obfervations on Blindness, and on the Employment of the other Senses to supply the Loss of Sight. By Mr. Bew,
The Author of this paper endeavours to trace the progress, and mark the degrees of perfection, to which blind people have carried the exertions of the other fenics in order to compensate for,