operations, in our active principles, and in our actions themselves, that, as faith in things divine is represented as the main spring in the life of a Christian, so belief in general is the main spring in the life of a man. That men often believe what there is no just ground to believe, and thereby are led into hurtful errors, is too evident to be denied. And, on the other hand, that there are just grounds of belief can as little be doubted by any man who is not a perfect sceptic.

We give the name of evidence to whatever is a ground of belief. To believe without evidence is a weakness which every man is concerned to avoid, and which every man wishes to avoid. Nor is it in a man's power to believe anything longer than he thinks he has evidence.

What this evidence is, is more easily felt than described. Those who never reflected upon its nature, feel its influence in governing their belief. It is the business of the logician to explain its nature, and to distinguish its various kinds and degrees; but every man of understanding can judge of it, and commonly judges right, when the evidence is fairly laid before him, and his mind is free from prejudice. A man who knows nothing of the theory of vision may have a good eye; and a man who never speculated about evidence in the abstract may have a good judgment. [272]

The common occasions of life lead us to distinguish evidence into different kinds, to which we give names that are well understood; such as the evidence of sense, the evidence of memory, the evidence of consciousness, the evidence of testimony, the evidence of axioms, the evidence of reasoning. All men of common understanding agree that each of these kinds of evidence may afford just ground of belief, and they agree very generally in the circumstances that strengthen or weaken them.

to one.

Philosophers have endeavoured, by analysing the different sorts of evidence, to find out some common nature wherein they all agree, and thereby to reduce them all This was the aim of the schoolmen in their intricate disputes about the criterion of truth. Des Cartes placed this criterion of truth in clear and distinct perception, and laid it down as a maxim, that whatever we clearly and distinctly perceive to be true, is true; but it is difficult to know what he understands by clear and distinct perception in this maxim. Mr Locke placed it in a perception of the agreement or disagreement of our ideas, which perception is immediate in intuitive knowledge, and by the intervention of other ideas in reasoning.

I confess that, although I have, as I think, a distinct notion of the different

kinds of evidence above-mentioned, and, perhaps, of some others, which it is unnecessary here to enumerate, yet I am not able to find any common nature to which they may all be reduced. They seem to me to agree only in this, that they are all fitted by Nature to produce belief in the human mind, some of them in the highest degree, which we call certainty, others in various degrees according to circumstances. I shall take it for granted that the evidence of sense, when the proper circumstances concur, is good evidence, and a just ground of belief. My intention in this place is only to compare it with the other kinds that have been mentioned, that we may judge whether it be reducible to any of them, or of a nature peculiar to itself. [273]

First, It seems to be quite different from the evidence of reasoning. All good evidence is commonly called reasonable evidence, and very justly, because it ought to govern our belief as reasonable creatures. And, according to this meaning, I think the evidence of sense no less reasonable than that of demonstration.* If Nature give us information of things that concern us, by other means than by reasoning, reason itself will direct us to receive that information with thankfulness, and to make the best use of it.

But, when we speak of the evidence of reasoning as a particular kind of evidence, it means the evidence of propositions that are inferred by reasoning, from propositions already known and believed. Thus, the evidence of the fifth proposition of the first book of Euclid's Elements consists in this, That it is shewn to be the necessary consequence of the axioms, and of the preceding propositions. In all reasoning, there must be one or more premises, and a conclusion drawn from them. And the premises are called the reason why we must believe the conclusion which we see to follow from them.

That the evidence of sense is of a different kind, needs little proof. No man seeks a reason for believing what he sees or feels; and, if he did, it would be difficult to find one. But, though he can give no reason for believing his senses, his belief remains as firm as if it were grounded on demonstration.

Many eminent philosophers, thinking it unreasonable to believe when they could not shew a reason, have laboured to furnish us with reasons for believing our senses; but their reasons are very insufficient, and will not bear examination. Other philoso

διανοίας. Aristotle. Προσέχειν οὐ δεῖ πάντα τοῖς διὰ * Ζητεῖν λόγον ἀφέντας τὴν αἴσθησιν, ἀῤῥωςία τίς ἐξι

τῶν λόγων. ἀλλὰ πολλάκις μᾶλλον τοῖς φαινομένοις. Ι. Τῇ αἰσθήσει μᾶλλον ἢ τῷ λόγῳ πιστευτέον καὶ τοῖς λόγοις, ἐὰν ὁμολογούμενα δεικνύωσι τοῖς φαινομένοις. Id. Η αἴσθησις ἐπισήμης έχει δύναμιν.-Π.Η.

phers have shewn very clearly the fallacy | of these reasons, and have, as they imagine, discovered invincible reasons against this belief; but they have never been able either to shake it in themselves, or to convince others. [274] The statesman continues to plod, the soldier to fight, and the merchant to export and import, without being in the least moved by the demonstrations that have been offered of the non-existence of those things about which they are so seriously employed. And a man may as soon, by reasoning, pull the moon out of her orbit, as destroy the belief of the objects of sense. Shall we say, then, that the evidence of sense is the same with that of axioms, or self-evident truths? I answer, First, That, all modern philosophers seem to agree that the existence of the objects of sense is not self-evident, because some of them have endeavoured to prove it by subtle reasoning, others to refute it. Neither of these can consider it as self-evident.

Secondly, I would observe that the word axiom is taken by philosophers in such a sense as that the existence of the objects of sense cannot, with propriety, be called an axiom. They give the name of axiom only to self-evident truths, that are necessary, and are not limited to time and place, but must be true at all times and in all places. The truths attested by our senses are not of this kind; they are contingent, and limited to time and place.

Thus, that one is the half of two, is an axiom. It is equally true at all times and in all places. We perceive, by attending to the proposition itself, that it cannot but be true; and, therefore, it is called an eternal, necessary, and immutable truth. That there is at present a chair on my right hand, and another on my left, is a truth attested by my senses; but it is not necessary, nor eternal, nor immutable. It may not be true next minute; and, therefore, to call it an axiom would, I apprehend, be to deviate from the common use of the word. [275]

Thirdly, If the word axiom be put to signify every truth which is known immediately, without being deduced from any antecedent truth, then the existence of the objects of sense may be called an axiom; for my senses give me as immediate conviction of what they testify, as my understanding gives of what is commonly called an axiom.

There is, no doubt, an analogy between the evidence of sense and the evidence of testimony. Hence, we find, in all languages, the analogical expressions of the testimony of sense, of giving credit to our senses, and the like. But there is a real difference between the two, as well as a similitude. In believing upon testimony, we rely upon the authority of a person who

testifies; but we have no such authority for believing our senses.

Shall we say, then, that this belief is the inspiration of the Almighty? I think this may be said in a good sense; for I take it to be the immediate effect of our constitution, which is the work of the Almighty. But, if inspiration be understood to imply a persuasion of its coming from God, our belief of the objects of sense is not inspiration; for a man would believe his senses though he had no notion of a Deity. He who is persuaded that he is the workmanship of God, and that it is a part of his constitution to believe his senses, may think that a good reason to confirm his belief. But he had the belief before he could give this or any other reason for it.

If we compare the evidence of sense with that of memory, we find a great resemblance, but still some difference. I remember distinctly to have dined yesterday with such a company. What is the meaning of this? It is, that I have a distinct conception and firm belief of this past event; not by reasoning, not by testimony, but immediately from my constitution. And I give the name of memory to that part of my constitution by which I have this kind of conviction of past events. [276]

I see a chair on my right hand. What is the meaning of this? It is, that I have, by my constitution, a distinct conception and firm belief of the present existence of the chair in such a place and in such a position; and I give the name of seeing to that part of my constitution by which I have this immediate conviction. The two operations agree in the immediate conviction which they give. They agree in this also, that the things believed are not necessary, but contingent, and limited to time and place. But they differ in two respects :-First, That memory has something for its object that did exist in time past; but the object of sight, and of all the senses, must be something which exists at present;-and, Secondly, That I see by my eyes, and only when they are directed to the object, and when it is illuminated. But my memory is not limited by any bodily organ that I know, nor by light and darkness, though it has its limitations of another kind.*

These differences are obvious to all men, and very reasonably lead them to consider seeing and remembering as operations specifically different. But the nature of the evidence they give, has a great resemblance.

There is a more important difference than these omitted. In memory, we cannot possibly be con scious or immediately cognisant of any object beyond the modifications of the ego itself. In perception, (if an immediate perception be allowed,) we must be conscious, or immediately cognisant, of some phæno. menon of the non-ego.-H.

A like difference and a like resemblance there is between the evidence of sense and that of consciousness, which I leave the reader to trace.

As to the opinion that evidence consists in a perception of the agreement or disagreement of ideas, we may have occasion to consider it more particularly in another place. Here I only observe, that, when taken in the most favourable sense, it may be applied with propriety to the evidence of reasoning, and to the evidence of some axioms. But I cannot see how, in any sense, it can be applied to the evidence of consciousness, to the evidence of memory, or to that of the senses.

When I compare the different kinds of evidence above-mentioned, I confess, after all, that the evidence of reasoning, and that of some necessary and self-evident truths, seems to be the least mysterious and the most perfectly comprehended; and therefore I do not think it strange that philosophers should have endeavoured to reduce all kinds of evidence to these. [277]

When I see a proposition to be self-evident and necessary, and that the subject is plainly included in the predicate, there seems to be nothing more that I can desire in order to understand why I believe it. And when I see a consequence that necessarily follows from one or more self-evident propositions, I want nothing more with regard to my belief of that consequence. The light of truth so fills my mind in these cases, that I can neither conceive nor desire anything more satisfying.

On the other hand, when I remember distinctly a past event, or see an object before my eyes, this commands my belief no less than an axiom. But when, as a philosopher, I reflect upon this belief, and want to trace it to its origin, I am not able to resolve it into necessary and self-evident axioms, or conclusions that are necessarily consequent upon them. I seem to want that evidence which I can best comprehend, and which gives perfect satisfaction to an inquisitive mind; yet it is ridiculous to doubt; and I find it is not in my power. An attempt to throw off this belief is like an attempt to fly, equally ridiculous and impracticable.

To a philosopher, who has been accustomed to think that the treasure of his knowledge is the acquisition of that reasoning power of which he boasts, it is no doubt humiliating to find that his reason can lay no claim to the greater part of it.

By his reason, he can discover certain abstract and necessary relations of things; but his knowledge of what really exists, or did exist, comes by another channel, which is open to those who cannot reason. He is led to it in the dark, and knows not how he came by it. [278]

It is no wonder that the pride of philosophy should lead some to invent vain theories in order to account for this knowledge; and others, who see this to be im practicable, to spurn at a knowledge they cannot account for, and vainly attempt to throw it off as a reproach to their understanding. But the wise and the humble will receive it as the gift of Heaven, and endeavour to make the best use of it.

CHAPTER XXI.

OF THE IMPROVEMENT OF THE SENSES.

Our senses may be considered in two views: first, As they afford us agreeable sensations, or subject us to such as are disagreeable; and, secondly, As they give us information of things that concern us.

In the first view, they neither require nor admit of improvement. Both the painful and the agreeable sensations of our external senses are given by nature for certain ends; and they are given in that degree which is the most proper for their end. By diminishing or increasing them, we should not mend, but mar the work of Nature.

Bodily pains are indications of some disorder or hurt of the body, and admonitions to use the best means in our power to prevent or remove their causes. As far as this can be done by temperance, exercise, regimen, or the skill of the physician, every man hath sufficient inducement to do it.

When pain cannot be prevented or removed, it is greatly alleviated by patience and fortitude of mind. While the mind is superior to pain, the man is not unhappy, though he may be exercised. It leaves no sting behind it, but rather matter of triumph and agreeable reflection, when borne properly, and in a good cause. [279] The Canadians have taught us that even savages may acquire a superiority to the most excruciating pains; and, in every region of the earth, instances will be found, where a sense of duty, of honour, or even of worldly interest, have triumphed over it.

It is evident that nature intended for man, in his present state, a life of labour and toil, wherein he may be occasionally exposed to pain and danger; and the happiest man is not he who has felt least of those evils, but he whose mind is fitted to bear them by real magnanimity.

Our active and perceptive powers are improved and perfected by use and exercise. This is the constitution of nature. But, with regard to the agreeable and disagreeable sensations we have by our senses, the very contrary is an established constitution of nature-the frequent repetition of them weakens their force. Sensations at first very

disagreeable, by use become tolerable, and at last perfectly indifferent. And those that are at first very agreeable, by frequent repetition become insipid, and at last, perhaps, give disgust. Nature has set limits to the pleasures of sense, which we cannot pass; and all studied gratifications of them, as it is mean and unworthy of a man, so it is foolish and fruitless.

The man who, in eating and drinking, and in other gratifications of sense, obeys the calls of Nature, without affecting delicacies and refinements, has all the enjoyment that the senses can afford. If one could, by a soft and luxurious life, acquire a more delicate sensibility to pleasure, it must be at the expense of a like sensibility to pain, from which he can never promise exemption, and at the expense of cherishing many diseases which produce pain.

The improvement of our external senses, as they are the means of giving us information, is a subject more worthy of our attention; for, although they are not the noblest and most exalted powers of our nature, yet they are not the least useful. [280] All that we know, or can know, of the material world, must be grounded upon their information; and the philosopher, as well as the day-labourer, must be indebted to them for the largest part of his knowledge.

Some of our perceptions by the senses may be called original, because they require no previous experience or learning; but the far greatest part is acquired, and the fruit of experience.

Three of our senses-to wit, smell, taste, and hearing-originally give us only certain sensations, and a conviction that these sensations are occasioned by some external object. We give a name to that quality of the object by which it is fitted to produce such a sensation, and connect that quality with the object, and with its other qualities.

Thus we learn, that a certain sensation of smell is produced by a rose; and that quality in the rose, by which it is fitted to produce this sensation, we call the smell of the rose. Here it is evident that the sensation is original. The perception that the rose has that quality which we call its smell, is acquired. In like manner, we learn all those qualities in bodies which we call their smell, their taste, their sound. These are all secondary qualities, and we give the same name to them which we give to the sensations they produce; not from any similitude between the sensation and the quality of the same name, but because the quality is signified to us by the sensation as its sign, and because our senses give us no other knowledge of the quality but that it is fit to produce such a sensation.

By the other two senses, we have much more ample information. By sight, we

learn to distinguish objects by their colour, in the same manner as by their sound, taste, and smell. By this sense, we perceive visible objects to have extension in two dimensions, to have visible figure and magnitude, and a certain angular distance from one another. These, I conceive, are the original perceptions of sight. [281]

By touch, we not only perceive the temperature of bodies as to heat and cold, † which are secondary qualities, but we perceive originally their three dimensions, their tangible figure and magnitude, their linear distance from one another, their hardness, softness, or fluidity. These qualities we originally perceive by touch only; but, by experience, we learn to perceive all or most of them by sight.

We learn to perceive, by one sense, what originally could have been perceived only by another, by finding a connection between the objects of the different senses. Hence the original perceptions, or the sensations of one sense become signs of whatever has always been found connected with them; and from the sign, the mind passes immediately to the conception and belief of the thing signified. And, although the connection in the mind between the sign and the thing signified by it, be the effect of custom, this custom becomes a second nature, and it is difficult to distinguish it from the original power of perception.

Thus, if a sphere of one uniform colour be set before me, I perceive evidently by my eye its spherical figure and its three dimensions. All the world will acknowledge that, by sight only, without touching it, I may be certain that it is a sphere; yet it is no less certain that, by the original power of sight, I could not perceive it to be a sphere, and to have three dimensions. The eye originally could only perceive two dimensions, and a gradual variation of colour on the different sides of the object.

It is experience that teaches me that the variation of colour is an effect of spherical convexity, and of the distribution of Ight and shade. But so rapid is the progress of the thought, from the effect to the cause, that we attend only to the last, and can hardly be persuaded that we do not immediately see the three dimensions of the sphere. [282]

Nay, it may be observed, that, in this case, the acquired perception in a manner effaces the original one; for the sphere is seen to be of one uniform colour, though originally there would have appeared a gradual variation of colour. But that ap

*See above, p. 123, col. b, note f, and p. 185, col. a, note *. Whether heat, cold, &c., be objects of touch or of a different sense, it is not here the place to inquire. -H.