these different parts, is very different: yet | we perceive the colour to be the same; we interpret the variety of appearance as a sign of light and shade, and not as a sign of real difference in colour. But, if the eye could be so far deceived as not to perceive the difference of light in the two parts of the cloth, we should, in that case, interpret the variety of appearance to signify a variety of colour in the parts of the cloth. Again, if we suppose a piece of cloth placed as before, but having the shaded part so much brighter in the colour that it gives the same appearance to the eye as the more enlightened part, the sameness of appearance will here be interpreted to signify a variety of colour, because we shall make allowance for the effect of light and shade.

When the real colour of an object is known, the appearance of it indicates, in some circumstances, the degree of light or shade; in others, the colour of the circumambient bodies, whose rays are reflected by it; and, in other circumstances, it indicates the distance or proximity of the object-as was observed in the last section; and by means of these, many other things are suggested to the mind. Thus, an unusual appearance in the colour of familiar objects may be the diagnostic of a disease in the spectator. The appearance of things in my room may indicate sunshine or cloudy weather, the earth covered with snow or blackened with rain. It hath been observed, that the colour of the sky, in a piece of painting, may indicate the country of the painter, because the Italian sky is really of a different colour from the Flemish.

It was already observed, that the original and acquired perceptions which we have by our senses, are the language of nature to man, which, in many respects, hath a great affinity to human languages. The instances which we have given of acquired perceptions, suggest this affinity-that, as, in human languages, ambiguities are often found, so this language of nature in our acquired perceptions is not exempted from them. We have seen, in vision particularly, that the same appearance to the eye, may, in different circumstances, indicate different things. Therefore, when the circumstances are unknown upon which the interpretation of the signs depends, their meaning must be ambiguous; and when the circumstances are mistaken, the meaning of the signs must also be mistaken.

This is the case in all the phænomena which we call fallacies of the senses; and particularly in those which are called fallacies in vision. The appearance of things to the eye always corresponds to the fixed laws of Nature; therefore, if we speak properly, there is no fallacy in the senses. Nature always speaketh the same language,

and useth the same signs in the same circumstances; but we sometimes mistake the meaning of the signs, either through ignorance of the laws of Nature, or through ignorance of the circumstances which attend the signs.*

To a man unacquainted with the principles of optics, almost every experiment that is made with the prism, with the magic lanthorn, with the telescope, with the microscope, seems to produce some fallacy in vision. Even the appearance of a common mirror, to one altogether unacquainted with the effects of it, would seem most remarkably fallacious. For how can a man be more imposed upon, than in seeing that before him which is really behind him? How can he be more imposed upon, than in being made to see himself several yards removed from himself? Yet children, even before they can speak their mothertongue, learn not to be deceived by these appearances. These, as well as all the other surprising appearances produced by optical glasses, are a part of the visual language, and, to those who understand the laws of Nature concerning light and colours, are in nowise fallacious, but have a distinct and true meaning.

Section XXIV.

OF THE ANALOGY BETWEEN PERCEPTION AND THE CREDIT WE GIVE TO HUMAN

TESTIMONY.†

The objects of human knowledge are innumerable; but the channels by which it is conveyed to the mind are few. Among these, the perception of external things by our senses, and the informations which we receive upon human testimony, are not the least considerable; and so remarkable is the analogy between these two, and the analogy between the principles of the mind which are subservient to the one and those which are subservient to the other, that, without further apology, we shall consider them together.

In the testimony of Nature given by the senses, as well as in human testimony given by language, things are signified to us by signs: and in one as well as the other, the mind, either by original principles or by custom, passes from the sign to the conception and belief of the things signified.

We have distinguished our perceptions

This is the doctrine of Aristotle; who holds that the senses never deceive us in relation to their proper objects.-H.

+ Compare Mr Stewart's" Elements," vol. I, ch. ii, 4, p. 247. Second edition. Campbell "On Miracles," Part I., § 1. Smith's Theory of Moral Sentiment," vol. 11, p. 382. Sixth edition.➡

H.

The signs in original perception are sensations, of which Nature hath given us a great variety, suited to the variety of the things signified by them. Nature hath established a real connection between the signs and the things signified; and Nature hath also taught us the interpretation of the signs-so that, previous to experience, the sign suggests the thing signified, and create the belief of it.

The signs in natural language are features of the face, gestures of the body, and modulations of the voice; the variety of which is suited to the variety of the things signified by them. Nature hath established a real connection between these signs, and the thoughts and dispositions of the mind which are signified by them; and Nature hath taught us the interpretation of these signs; so that, previous to experience, the signs suggest the thing signified, and create the belief of it.

A man in company, without doing good or evil, without uttering an articulate sound, may behave himself gracefully, civilly, politely; or, on the contrary, meanly, rudely, and impertinently. We see the dispositions of his mind by their natural signs in his countenance and behaviour, in the same manner as we perceive the figure and other qualities of bodies by the sensations which nature hath connected with them.

The signs in the natural language of the human countenance and behaviour, as well as the signs in our original perceptions, have the same signification in all climates and in all nations; and the skill of interpreting them is not acquired, but innate.

In acquired perception, the signs are either sensations, or things which we perceive by means of sensations. The connection between the sign and the thing signified, is established by nature; and we discover this connection by experience; but not without the aid of our original perceptions, or of those which we have already acquired. After this connection is discovered, the sign, in like manner as in original perception, always suggests the things signified, and creates the belief of

it.

In artificial language, the signs are articulate sounds, whose connection with the things signified by them, is established by the will of men; and, in learning our mother tongue, we discover this connection by experience; but not without the aid of natural language, or of what we had before

Our original perceptions are few, compared with the acquired; but, without the former, we could not possibly attain the latter. In like manner, natural language is scanty, compared with artificial; but, without the former, we could not possibly attain the latter.

Our original perceptions, as well as the natural language of human features and gestures, must be resolved into particular principles of the human constitution. Thus, it is by one particular principle of our constitution that certain features express anger; and, by another particular principle, that certain features express benevolence. It is, in like manner, by one particular principle of our constitution that a certain sensation signifies hardness in the body which I handle; and it is by another particular principle that a certain sensation signifies motion in that body.

But our acquired perceptions, and the information we receive by means of artificial language, must be resolved into general principles of the human constitution. When a painter perceives that this picture is the work of Raphael, that the work of Titian; a jeweller, that this is a true diamond, that a counterfeit ; a sailor, that this is a ship of five hundred ton, that of four hundred; these different acquired perceptions are produced by the same general principles of the human mind, which have a different operation in the same person according as they are variously applied, and in different persons according to the diversity of their education and manner of life. In like manner, when certain articulate sounds convey to my mind the knowledge of the battle of Pharsalia, and others, the knowledge of the battle of Poltowa-when a Frenchman and an Englishman receive the same information by different articulate sounds the signs used in these different cases, produce the knowledge and belief of the things signified, by means of the same general principles of the human constitution.

Now, if we compare the general principles of our constitution, which fit us for receiving information from our fellow-creatures by language, with the general principles which fit us for acquiring the perception of things by our senses, we shall find them to be very similar in their nature and manner of operation.

When we begin to learn our mothertongue, we perceive, by the help of natural language, that they who speak to us use certain sounds to express certain things we imitate the same sounds when we would

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express the same things; and find that we are understood.

But here a difficulty occurs which merits our attention, because the solution of it leads to some original principles of the human mind, which are of great importance, and of very extensive influence. We know by experience that men have used such words to express such things; but all experience is of the past, and can, of itself, give no notion or belief of what is future. How come we, then, to believe, and to rely upon it with assurance, that men, who have it in their power to do otherwise, will continue to use the same words when they think the same things? Whence comes this knowledge and belief- this foresight, we ought rather to call it-of the future and voluntary actions of our fellow-creatures? Have they promised that they will never impose upon us by equivocation or falsehood? No, they have not. And, if they had, this would not solve the difficulty; for such promise must be expressed by words or by other signs; and, before we can rely upon it, we must be assured that they put the usual meaning upon the signs which express that promise. No man of common sense ever thought of taking a man's own word for his honesty; and it is evident that we take his veracity for granted when we lay any stress upon his word or promise. I might add, that this reliance upon the declarations and testimony of men is found in children long before they know what a promise is.

There is, therefore, in the human mind an early anticipation, neither derived from experience, nor from reason, nor from any compact or promise, that our fellow-creatures will use the same signs in language, when they have the same sentiments.

This is, in reality, a kind of prescience of human actions; and it seems to me to be an original principle of the human constitution, without which we should be incapable of language, and consequently incapable of instruction.

The wise and beneficent Author of Nature, who intended that we should be social creatures, and that we should receive the greatest and most important part of our knowledge by the information of others, hath, for these purposes, implanted in our natures two principles that tally with each other.

The first of these principles is, a propensity to speak truth, and to use the signs of language so as to convey our real sentiments. This principle has a powerful operation, even in the greatest liars; for where they lie once, they speak truth a hundred times. Truth is always uppermost, and is the natural issue of the mind. It requires no art or training, no inducement

or temptation, but only that we yield to a natural impulse. Lying, on the contrary, is doing violence to our nature; and is never practised, even by the worst men, without some temptation. Speaking truth is like using our natural food, which we would do from appetite, although it answered no end; but lying is like taking physic, which is nauseous to the taste, and which no man takes but for some end which he cannot otherwise attain.

If it should be objected, That men may be influenced by moral or political considerations to speak truth, and, therefore, that their doing so is no proof of such an original principle as we have mentioned-I answer, First, That moral or political considerations can have no influence until we arrive at years of understanding and reflec tion; and it is certain, from experience, that children keep to truth invariably, before they are capable of being influenced by such considerations. Secondly, When we are influenced by moral or political considerations, we must be conscious of that influence, and capable of perceiving it upon reflection. Now, when I reflect upon my actions most attentively, I am not conscious that, in speaking truth, I am influenced on ordinary occasions by any motive, moral or political. I find that truth is always at the door of my lips, and goes forth spontaneously, if not held back. It requires neither good nor bad intention to bring it forth, but only that I be artless and undesigning. There may indeed be temptations to falsehood, which would be too strong for the natural principle of veracity, unaided by principles of honour or virtue; but where there is no such temptation, we speak truth by instinct-and this instinct is the principle I have been explaining.

By this instinct, a real connection is formed between our words and our thoughts, and thereby the former become fit to be signs of the latter, which they could not otherwise be. And although this counection is broken in every instance of lying and equivocation, yet these instances being comparatively few, the authority of human testimony is only weakened by them, but not destroyed.

Another original principle implanted in us by the Supreme Being, is a disposition to confide in the veracity of others, and to believe what they tell us. This is the counterpart to the former; and, as that may be called the principle of veracity, we shall, for want of a more proper name, call this the principle of credulity. It is unlimited in children, until they meet with instances of deceit and falsehood; and it retains a very considerable degree of strength through life.

If Nature had left the mind of the speaker

in æquilibrio, without any inclination to the side of truth more than to that of falsehood, children would lie as often as they speak truth, until reason was so far ripened as to suggest the imprudence of lying, or conscience, as to suggest its immorality. And if Nature had left the mind of the hearer in æquilibrio, without any inclination to the side of belief more than to that of disbelief, we should take no man's word until we had positive evidence that he spoke truth. His testimony would, in this case, have no more authority than his dreams; which may be true or false, but no man is disposed to believe them, on this account, that they were dreamed. It is evident that, in the matter of testimony, the balance of human judgment is by nature inclined to the side of belief; and turns to that side of itself, when there is nothing put into the opposite scale. If it was not so, no proposition that is uttered in discourse would be believed, until it was examined and tried by reason; and most men would be unable to find reasons for believing the thousandth part of what is told them. Such distrust and incredulity would deprive us of the greatest benefits of society, and place us in a worse condition than that of savages.

Children, on this supposition, would be absolutely incredulous, and, therefore, absolutely incapable of instruction: those who had little knowledge of human life, and of the manners and characters of men, would be in the next degree incredulous: and the most credulous men would be those of greatest experience, and of the deepest penetration; because, in many cases, they would be able to find good reasons for believing testimony, which the weak and the ignorant could not discover.

In a word, if credality were the effect of reasoning and experience, it must grow up and gather strength, in the same proportion as reason and experience do. But, if it is the gift of Nature, it will be strongest in childhood, and limited and restrained by experience; and the most superficial view of human life shews, that the last is really the case, and not the first.

It is the intention of Nature, that we should be carried in arms before we are able to walk upon our legs; and it is likewise the intention of Nature, that our belief should be guided by the authority and reason of others, before it can be guided by our own reason. The weakness of the infant, and the natural affection of the mother, plainly indicate the former; and the natural credulity of youth, and authority of age, as plainly indicate the latter. The infant, by

See, contra, Priestley's " Examinatio," p. 86. "Brown's Lect." lect, lxxxiv.

proper nursing and care, acquires strength to walk without support. Reason hath likewise her infancy, when she must be carried in arms: then she leans entirely upon authority, by natural instinct, as if she was conscious of her own weakness; and, without this support, she becomes vertiginous. When brought to maturity by proper culture, she begins to feel her own strength, and leans less upon the reason of others; she learns to suspect testimony in some cases, and to disbelieve it in others; and sets bounds to that authority to which she was at first entirely subject. But still, to the end of life, she finds a necessity of borrowing light from testimony, where she has none within herself, and of leaning, in some degree, upon the reason of others, where she is conscious of her own imbecility.

And as, in many instances, Reason, even in her maturity, borrows aid from testimony, so in others she mutually gives aid to it, and strengthens its authority. For as we find good reason to reject testimony in some cases, so in others we find good reason to rely upon it with perfect security, in our most important concerns. The character, the number, and the disinterestedness of witnesses, the impossibility of collusion, and the incredibility of their concurring in their testimony without collusion, may give an irresistible strength to testimony, compared to which its native and intrinsic authority is very inconsiderable.

Having now considered the general principles of the human mind which fit us for receiving information from our fellow-creatures, by the means of language, let us next consider the general principles which fit us for receiving the information of Nature by our acquired perceptions.

It is undeniable, and indeed is acknowledged by all, that when we have found two things to have been constantly conjoined in the course of nature, the appearance of one of them is immediately followed by the conception and belief of the other. The former becomes a natural sign of the latter; and the knowledge of their constant conjunction in time past, whether got by experience or otherwise, is sufficient to make us rely with assurance upon the continuance of that conjunction.

This process of the human mind is so familiar that we never think of inquiring into the principles upon which it is founded. We are apt to conceive it as a self-evident truth, that what is to come must be similar to what is past. Thus, if a certain degree of cold freezes water to-day, and has been known to do so in all time past, we have no doubt but the same degree of cold will freeze water to-morrow, or a year hence. That this is a truth which all men believe as