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without the exercise of reason; we are improvement, is, by additional organs, or inmerely animal before we are rational crea- struments contrived by art. By the inventures; and it is necessary for our preserva- tion of optical glasses, and the gradual imtion, that we should believe many things be-provement of them, the natural power of fore we can reason. How then is our belief vision is wonderfully improved, and a vast to be regulated before we have reason to addition made to the stock of knowledge regulate it? [285] Has nature left it to be which we acquire by the eye. By speakingregulated by chance? By no means. It is trumpets and ear-trumpets some improveregulated by certain principles, which are ment has been made in the sense of hearing. parts of our constitution; whether they Whether by similar inventions the other ought to be called animal principles, or in- senses may be improved, seems uncertain. stinctive principles, or what name we give to them, is of small moment; but they are certainly different from the faculty of reason they do the office of reason while it is in its infancy, and must, as it were, be carried in a nurse's arms, and they are leadingstrings to it in its gradual progress.

From what has been said, I think it appears that our original powers of perceiving objects by our senses receive great improvement by use and habit; and without this improvement, would be altogether insufficient for the purposes of life. The daily occurrences of life not only add to our stock of knowledge, but give additional perceptive powers to our senses; and time gives us the use of our eyes and ears, as well as of our hands and legs.

This is the greatest and most important improvement of our external senses. It is to be found in all men come to years of understanding, but it is various in different persons according to their different occupations, and the different circumstances in which they are placed. Every artist requires an eye as well as a hand in his own profession; his eye becomes skilled in perceiving, no less than his hand in executing, what belongs to his employment.

Besides this improvement of our senses, which nature produces without our intention, there are various ways in which they may be improved, or their defects remedied by art. As, first, by a due care of the organs of sense, that they be in a sound and natural state. This belongs to the department of the medical faculty.

Secondly, By accurate attention to the objects of sense. The effects of such attention in improving our senses, appear in every art. The artist, by giving more attention to certain objects than others do, by that means perceives many things in those objects which others do not. [286] Those who happen to be deprived of one sense, frequently supply that defect in a great degree, by giving more accurate attention to the objects of the senses they have. The blind have often been known to acquire uncommon acuteness in distinguishing things by feeling and hearing; and the deaf are uncommonly quick in reading men's thoughts in their countenance.

A third way in which our senses admit of

A fourth method by which the informa tion got by our senses may be improved, is, by discovering the connection which nature hath established between the sensible qualities of objects, and their more latent qualities.

By the sensible qualities of bodies, I understand those that are perceived immediately by the senses, such as their colour, figure, feeling, sound, taste, smell. The various modifications and various combinations of these, are innumerable; so that there are hardly two individual bodies in Nature that may not be distinguished by their sensible qualities.

The latent qualities are such as are not immediately discovered by our senses; but discovered sometimes by accident, sometimes by experiment or observation. The most important part of our knowledge of bodies is the knowledge of the latent qualities of the several species, by which they are adapted to certain purposes, either for food, or medicine, or agriculture, or for the materials or utensils of some art or manufacture. [287]

I am taught that certain species of bodies have certain latent qualities; but how shall I know that this individual is of such a species? This must be known by the sensible qualities which characterise the species. I must know that this is bread, and that wine, before I eat the one or drink the other. I must know that this is rhubarb, and that opium, before I use the one or the other for medicine.

It is one branch of human knowledge to know the names of the various species of natural and artificial bodies, and to know the sensible qualities by which they are ascertained to be of such a species, and by which they are distinguished from one another. It is another branch of knowledge to know the latent qualities of the several species, and the uses to which they are subservient.

The man who possesses both these branches is informed, by his senses, of innumerable things of real moment which are hid from those who possess only one, or neither. This is an improvement in the information got by our senses, which must keep pace with the improvements made in natural history, in natural philosophy, and in the arts.

It would be an improvement still higher if we were able to discover any connection between the sensible qualities of bodies and their latent qualities, without knowing the species, or what may have been discovered with regard to it.

Some philosophers, of the first rate, have made attempts towards this noble improvement, not without promising hopes of success. Thus, the celebrated Linnæus has attempted to point out certain sensible qualities by which a plant may very probably be concluded to be poisonous without knowing its name or species. He has given several other instances, wherein certain medical and economical virtues of plants are indicated by their external appearances. Sir Isaac Newton hath attempted to shew that, from the colours of bodies, we may form a probable conjecture of the size of their constituent parts, by which the rays of light are reflected. [288]

No man can pretend to set limits to the discoveries that may be made by human genius and industry, of such connections between the latent and the sensible qualities of bodies. A wide field here opens to our view, whose boundaries no man can ascertain, of improvements that may hereafter be made in the information conveyed to us by our senses.

CHAPTER XXII.

OF THE FALLACY OF THE SENSES.

COMPLAINTS of the fallacy of the senses have been very common in ancient and in modern times, especially among the philosophers. And, if we should take for granted all that they have said on this subject, the natural conclusion from it might seem to be, that the senses are given to us by some malignant demon on purpose to delude us, rather than that they are formed by the wise and beneficent Author of Nature, to give us true information of things necessary to our preservation and happiness.

The whole sect of atomists among the ancients, led by Democritus, and afterwards by Epicurus, maintained that all the qualities of bodies which the moderns call secondary qualities-to wit, smell, taste, sound, colour, heat, and cold-are mere illusions of sense, and have no real existence.* Plato maintained that we can attain no real knowledge of material things; and that eternal and immutable ideas are the only objects of real knowledge. The academics and scepties anxiously sought for arguments to prove the fallaciousness of our senses, in order to support their favourite doctrine,

*Not correctly stated. See above, p. 316, note §. The Epicureans denied the fallacy of Sense.-H.

that even in things that seem most evident, we ought to withhold assent. [289]

Among the Peripatetics we find frequent complaints that the senses often deceive us, and that their testimony is to be suspected, when it is not confirmed by reason, by which the errors of sense may be corrected. This complaint they supported by many commonplace instances: such as, the crooked appearance of an oar in water; objects being magnified, and their distance mistaken, in a fog; the sun and moon appearing about a foot or two in diameter, while they are really thousands of miles; a square tower being taken at a distance to be round. These, and many similar appearances, they thought to be sufficiently accounted for from the fallacy of the senses: and thus the fallacy of the senses was used as a decent cover to conceal their ignorance of the real causes of such phænomena, and served the same purpose as their occult qualities and substantial forms.

Des Cartes and his followers joined in the same complaint. Antony le Grand, a philosopher of that sect, in the first chapter of his Logic, expresses the sentiments of the sect as follows: "Since all our senses are fallacious, and we are frequently deceived by them, common reason advises that we should not put too much trust in them, nay, that we should suspect falsehood in everything they represent; for it is imprudence and temerity to trust to those who have but once deceived us; and, if they err at any time, they may be believed always to err. They are given by nature for this purpose only to warn us of what is useful and what is hurtful to us. The order of Nature is perverted when we put them to any other use, and apply them for the knowledge of truth."

When we consider that the active part of mankind, in all ages from the beginning of the world, have rested their most important concerns upon the testimony of sense, it will be very difficult to reconcile their conduct with the speculative opinion so generally entertained of the fallaciousness of the senses. [290] And it seems to be a very unfavourable account of the workmanship of the Supreme Being, to think that he has given us one faculty to deceive us--to wit, our senses; and another faculty

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our external senses-sensation, and the perception of external objects.

It is impossible that there can be any fallacy in sensation : for we are conscious of all our sensations, and they can neither be any other in their nature, nor greater or less in their degree than we feel them. It is impossible that a man should be in pain, when he does not feel pain; and when he feels pain, it is impossible that his pain should not be real, and in its degree what it is felt to be; and the same thing may be said of every sensation whatsoever. An agreeable or an uneasy sensation may be forgot when it is past, but when it is present, it can be nothing but what we feel.

If, therefore, there be any fallacy in our senses, it must be in the perception of external objects, which we shall next con

sider.

And here I grant that we can conceive powers of perceiving external objects more perfect than ours, which, possibly, beings of a higher order may enjoy. We can perceive external objects only by means of bodily organs; and these are liable to various disorders, which sometimes affect our powers of perception. The nerves and brain, which are interior organs of perception, are likewise liable to disorders, as every part of the human frame is. [291]

The imagination, the memory, the judging and reasoning powers, are all liable to be hurt, or even destroyed, by disorders of the body, as well as our powers of perception; but we do not on this account call them fallacious.

Our senses, our memory, and our reason, are all limited and imperfect-this is the lot of humanity: but they are such as the Author of our being saw to be best fitted for us in our present state. Superior natures may have intellectual powers which we have not, or such as we have, in a more perfect degree, and less liable to accidental disorders; but we have no reason to think that God has given fallacious powers to any of his creatures: this would be to think dishonourably of our Maker, and would lay a foundation for universal scepticism.

The appearances commonly imputed to the fallacy of the senses are many and of different kinds; but I think they may be reduced to the four following classes.

| feit guinea for a true one, he says his senses deceived him; but he lays the blame where it ought not to be laid : for we may ask him, Did your senses give a false testimony of the colour, or of the figure, or of the impression? No. But this is all that they testified, and this they testified truly : From these premises you concluded that it was a true guinea, but this conclusion does not follow; you erred, therefore, not by relying upon the testimony of sense, but by judging rashly from its testimony. [292] Not only are your senses innocent of this error, but it is only by their information that it can be discovered. If you consult them properly, they will inform you that what you took for a guinea is base metal, or is deficient in weight, and this can only be known by the testimony of sense.

I remember to have met with a man who thought the argument used by Protestants against the Popish doctrine of transubstantiation, from the testimony of our senses, inconclusive; because, said he, instances may be given where several of our senses may deceive us How do we know then that there may not be cases wherein they all deceive us, and no sense is left to detect the fallacy? I begged of him to know an instance wherein several of our senses deceive us. I take, said he, a piece of soft turf; I cut it into the shape of an apple; with the essence of apples, I give it the smell of an apple; and with paint, I can give it the skin and colour of an apple. Here then is a body, which, if you judge by your eye, by your touch, or by your smell, is an apple.

My

The

To this I would answer, that no one of our senses deceives us in this case. sight and touch testify that it has the shape and colour of an apple: this is true. sense of smelling testifies that it has the smell of an apple: this is likewise true, and is no deception. Where then lies the deception? It is evident it lies in this-that because this body has some qualities belonging tean apple I conclude that it is an apple. This is a fallacy, not of the senses, but of inconclusive reasoning.

Many false judgments that are accounted deceptions of sense, arise from our mistaking relative motion for real or absolute motion. These can be no deceptions of sense, because by our senses we perceive only the relative motions of bodies; and it is by reasoning that we infer the real from the relative which we perceive. A little reflection may satisfy us of this. [293]

First, Many things called deceptions of the senses are only conclusions rashly drawn from the testimony of the senses. In these cases the testimony of the senses is true, but we rashly draw a conclusion from it, It was before observed, that we perceive which does not necessarily follow. We are extension to be one sensible quality of disposed to impute our errors rather to false bodies, and thence are necessarily led to information than to inconclusive reasoning, conceive space, though space be of itself and to biame our senses for the wrong con- no object of sense. When a body is reclusions we draw from their testimony. moved out of its place, the space which it Thus, when a man has taken a counter-filled remains empty till it is filled by some

other body, and would remain if it should never be filled. Before any body existed, the space which bodies now occupy was empty space, capable of receiving bodies; for no body can exist where there is no space to contain it. There is space therefore whereever bodies exist, or can exist.

Hence it is evident that space can have no limits. It is no less evident that it is immovable. Bodies placed in it are movable, but the place where they were cannot be moved; and we can as easily conceive a thing to be moved from itself, as one part of space brought nearer to or removed farther from another.

The space, therefore, which is unlimited and immovable, is called by philosophers absolute space. Absolute or real motion is

a change of place in absolute space. Our senses do not testify the absolute motion or absolute rest of any body. When one body removes from another, this may be discerned by the senses; but whether any body keeps the same part of absolute space, we do not perceive by our senses. When one body seems to remove from another, we can infer with certainty that there is absolute motion, but whether in the one or the other, or partly in both, is not discerned by sense.

Of all the prejudices which philosophy contradicts, I believe there is none so general as that the earth keeps its place unmoved. This opinion seems to be universal, till it is corrected by instruction or by philosophical speculation. Those who have any tincture of education are not now in danger of being held by it, but they find at first a reluctance to believe that there are antipodes; that the earth is spherical, and turns round its axis every day, and round the sun every year they can recollect the time when reason struggled with prejudice upon these points, and prevailed at length, but not without some effort. [294]

The cause of a prejudice so very general is not unworthy of investigation. But that is not our present business. It is sufficient to observe, that it cannot justly be called a fallacy of sense; because our senses testify only the change of situation of one body in relation to other bodies, and not its change of situation in absolute space. It is only the relative motion of bodies that we perceive, and that we perceive truly. It is the province of reason and philosophy, from the relative motions which we perceive, to collect the real and absolute motions which produce them.

All motion must be estimated from some point or place which is supposed to be at rest. We perceive not the points of absolute space, from which real and absolute motion must be reckoned: And there are obvious reasons that lead mankind in the

state of ignorance, to make the earth the fixed place from which they may estimate the various motions they perceive. The custom of doing this from infancy, and of using constantly a language which supposes the earth to be at rest, may perhaps be the cause of the general prejudice in favour of this opinion.

Thus it appears that, if we distinguish accurately between what our senses really and naturally testify, and the conclusions which we draw from their testimony by reasoning, we shall find many of the errors, called fallacies of the senses, to be no fallacy of the senses, but rash judgments, which are not to be imputed to our senses.

Secondly, Another class of errors imputed to the fallacy of the senses, are those which we are liable to in our acquired perceptions. Acquired perception is not properly the testimony of those senses which God hath given us, but a conclusion drawn from what the senses testify. [295] In our past experience, we have found certain things conjoined with what our senses testify. We are led by our constitution to expect this conjunction in time to come; and when we have often found it in our experience to happen, we acquire a firm belief that the things which we have found thus conjoined, are connected in nature, and that one is a sign of the other. The appearance of the sign immediately produces the belief of its usual attendant, and we think we perceive the one as well as the other.

That such conclusions are formed even in infancy, no man can doubt: nor is it less certain that they are confounded with the natural and immediate perceptions of sense, and in all languages are called by the same name. We are therefore authorized by language to call them perception, and must often do so, or speak unintelligibly. But philosophy teaches us, in this, as in many other instances, to distinguish things which the vulgar confound. I have therefore given the name of acquired perception to such conclusions, to distinguish them from what is naturally, originally, and immediately testified by our senses. Whether this acquired perception is to be resolved into some process of reasoning, of which we have lost the remembrance, as some philosophers think, or whether it results from some part of our constitution distinct from reason, as I rather believe, does not concern the present subject. If the first of these opinions be true, the errors of acquired perception will fall under the first class before mentioned. If not, it makes a distinct class by itself. But whether the one or the other be true, it must be observed that the errors of acquired per-ception are not properly fallacies of our senses.

Thus, when a globe is set before me, I perceive by my eyes that it has three dimensions and a spherical figure. To say that this is not perception, would be to reject the authority of custom in the use of words, which no wise man will do: but that it is not the testimony of my sense of seeing, every philosopher knows. I see only a circular form, having the light and colour distributed in a certain way over it. [296] But, being accustomed to observe this distribution of light and colour only in a spherical body, I immediately, from what I see, believe the object to be spherical, and say that I see or perceive it to be spherical. When a painter, by an exact imitation of that distribution of light and colour which I have been accustomed to see only in a real sphere, deceives me, so as to make me take that to be a real sphere which is only a painted one, the testimony of my eye is true -the colour and visible figure of the object is truly what I see it to be: the error lies in the conclusion drawn from what I seeto wit, that the object has three dimensions and a spherical figure. The conclusion is false in this case; but, whatever be the origin of this conclusion, it is not properly the testimony of sense.

To this class we must refer the judgments we are apt to form of the distance and magnitude of the heavenly bodies, and of terrestrial objects seen on high. The mistakes we make of the magnitude and distance of objects seen through optical glasses, or through an atmosphere uncommonly clear or uncommonly foggy, belong likewise to this class.

The errors we are led into in acquired perception are very rarely hurtful to us in the conduct of life; they are gradually corrected by a more enlarged experience, and a more perfect knowledge of the laws of Nature: and the general laws of our constitution, by which we are sometimes led into them, are of the greatest utility.

We come into the world ignorant of everything, and by our ignorance exposed to many dangers and to many mistakes. The regular train of causes and effects, which divine wisdom has established, and which directs every step of our conduct in advanced life, is unknown, until it is gradually discovered by experience. [297]

We must learn much from experience before we can reason, and therefore must be liable to many errors. Indeed, I apprehend, that, in the first part of life, reason would do us much more hurt than good. Were we sensible of our condition in that period, and capable of reflecting upon it, we should be like a man in the dark, surrounded with dangers, where every step he takes may be into a pit. Reason would direct him to sit down, and wait till he could see about him.

In like manner, if we suppose an infant endowed with reason, it would direct him to do nothing, till he knew what could be done with safety. This he can only know by experiment, and experiments are dangerous. Reason directs, that experiments that are full of danger should not be made without a very urgent cause. It would therefore make the infant unhappy, and hinder his improvement by experience.

Nature has followed another plan. The child, unapprehensive of danger, is led by instinct to exert all his active powers, to try everything without the cautious admonitions of reason, and to believe everything that is told him. Sometimes he suffers by his rashness what reason would have prevented but his suffering proves a salutary discipline, and makes him for the future avoid the cause of it. Sometimes he is imposed upon by his credulity; but it is of infinite benefit to him upon the whole. His activity and credulity are more useful qualities and better instructors than reason would be; they teach him more in a day than reason would do in a year; they furnish a stock of materials for reason to work upon; they make him easy and happy in a period of his existence when reason could only serve to suggest a thousand tormenting anxieties and fears: and he acts agreeably to the constitution and intention of nature even when he does and believes what reason would not justify. So that the wisdom and goodness of the Author of nature is no less conspicuous in withholding the exercise of our reason in this period, than in bestowing it when we are ripe for it. [298]

A third class of errors, ascribed to the fallacy of the senses, proceeds from ignorance of the laws of nature.

The laws of nature (I mean not moral but physical laws) are learned, either from our own experience, or the experience of others, who have had occasion to observe the course of nature.

Ignorance of those laws, or inattention to them, is apt to occasion false judgments with regard to the objects of sense, especially those of hearing and of sight; which false judgments are often, without good reason, called fallacies of sense.

Sounds affect the ear differently, according as the sounding body is before or behind us, on the right hand or on the left, near or at a great distance. We learn, by the manner in which the sound affects the ear, on what hand we are to look for the sounding body; and in most cases we judge right. But we are sometimes deceived by echoes, or by whispering galleries, or speaking trumpets, which return the sound, or alter its direction, or convey it to a distance without diminution.

The deception is still greater, because

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