ALL the systems of philosophers about our senses and their objects have split upon this rock, of not distinguish- ing properly sensations, which can have no existence but when they are felt, from the tlu'ngs suggested by them. Aristotle, with as distinguishing a head as ever applied to philosophical disquisitions, confounds these two; and makes every sensation to be the form, without the matter, of the thing perceived by it: as the impression of a seal upon wax has the form of the seal, but nothing of the matter of it; so he conceived our sensations to be impres- sions upon the mind, which bear the image, likeness, or form of the external thing perceived, without the matter of it. Colour, sound, and smell, as well as extension, figure, and hardness, are, according to him, various forms of matter: our sensations are the same forms imprinted on the mind, and perceived in its own intellect. It is evident from this, that Aristotle made no distinction between primary and secondary qualities of bodies, although that distinction was made by Democritus, Epicurus, and others of the ancients.
Des Cartes, Malebranche, and Locke revived the dis- tinction between primary and secondary qualities. But they made the secondaiy qualities mere sensations, and the primary ones resemblances of our sensations. They maintained, that colour, sound, and heat are not any thing in bodies, but sensations of the mind: at the same time they acknowledged some -particular texture or modi- 80 OF THE HUMAN MIND. [CHAP. V.
fication of the body to be the cause or occasion of those sensations; but to this modification they gave no name. Whereas, by the vulgar, the names of colour, heat, and sound are but rarely applied to the sensations, and most commonly to those unknown causes of them; as hath been already explained. The constitution of our nature leads us rather to attend to the things signified by the sensation than to the sensation itself, and to give a name to the former rather than to the latter. Thus we see, that with regard to secondary qualities, these philosophers thought with the vulgar, and with common sense. Their paradoxes were only an abuse of words. For when they maintain, as an important modern discovery, that there is no heat in the fire, they mean no more, than that the fire does not feel heat, which every one knew before.
With regard to primary qualities, these philosophers erred most grossly: they indeed believed the existence of those qualities; but they did not at all attend to the sen- sations that suggest them, which have no names, having been as little considered as if they had no existence. They were aware, that figure, extension, and hardness are perceived by means of sensations of touch; whence they rashly concluded, that these sensations must be images and resemblances of figure, extension, and hardness.
The received hypothesis of ideas naturally led them to this conclusion; and indeed cannot exist with any other; for, according to that hypothesis, external things must be perceived by means of images of them in the mind; and what can those images of external things in the mind be, but the sensations by which we perceive them?
This, however, was to draw a conclusion from an hypo- thesis against fact. We need not have recourse to any hypothesis to know what our sensations are, or what they are like. By a proper degree of reflection and attention, we may understand them perfectly, and be as certain that they are not like any quality of body as we can be that the toothach is not like a triangle. How a sensation should instantly make us conceive and believe the ex- istence of an external thing altogether unlike to it, I do SECT. VIII.] OF TOUCH. 81 not pretend to know; and when I say that the one sug- uc.sts the other, I mean not to explain the manner of their < onnection, but to express a fact, which every one may be conscious of; namely, that, by a law of our nature, -iich a conception and belief constantly and immediately follow the sensation.
Bishop Berkeley gave new light to this subject, by showing, that the qualities of an inanimate thing, such as matter is conceived to be, cannot resemble any sensation; that it is impossible to conceive any thing like the sensa- tions of our minds, but the 'sensations of other minds. Kvery one that attends properly to these sensations must assent to this; yet it had escaped all the philosophers that came before Berkeley; it had escaped, even the ingenious Locke, who had so much practised reflection on the opera- tions of his own mind. So difficult is it to attend pro- perly even to our own feelings. They are so accustomed to pass through the mind unobserved, and instantly to make way for that which nature intended them to signify, that it is extremely difficult to stop and survey them; and when we think we have acquired this power, perhaps the mind still fluctuates between the sensation and its associated quality, so that they mix together, find present something to the imagination that is compounded of both. Thus i:i a globe or cylinder, whose opposite sides are quite unlike in colour, if you turn it slowly, the colours are perfectly distinguishable, and their dissimilitude is manifest; but if it is turned fast, they lose their distinction, and seem to be of one and the same colour.
No succession can be more quick than that of tangible qualities to the sensations with which nature has asso- ciated them: But when one has once acquired the art of making them separate and distinct objects of thought, he will then clearly perceive, that the maxim of Bishop Berkeley above mentioned is self-evident; and that the features of the face are not more unlike to a passion of the mind which they indicate than the sensations of touch are to the primary qualities of body.
But let us observe what use the Bishop makes of this E3 82 OF THE HUMAN MIND. [CHAP. V.
important discovery: Why, he concludes, that we can have no conception of an inanimate substance, such as matter is conceived to be, or of any of its qualities; and that there is the strongest ground to believe that there is no existence in nature but minds, sensations, and ideas: If there is any other kind of existence, it must be what we neither have nor can have any conception of. But how does this follow? Why thus: We can have no concep- tion of any thing but what resembles some sensation or idea in our minds; but the sensations and ideas in our minds can resemble nothing but the sensations and ideas in other minds; therefore, the conclusion is evident. This argument, we see, leans upon two propositions. The last of them the ingenious author hath indeed made evident to all that understand his reasoning, and can attend to their own sensations: but the first proposition he never attempts to prove; it is taken from the doctrine of ideas, which hath been so universally received by philosophers, that it was thought to need no proof.
We may here again observe, that this acute writer argues from an hypothesis against fact, and against the common sense of mankind. That we can have no con- ception of any thing, unless there is some impression, sen- sation, or idea, in our minds which resembles it, is indeed an opinion which hath been very generally receiv ed among philosophers; but it is neither self-evident nor hath it been clearly proved: and therefore it had been more rea- sonable to call in question this doctrine of philosophers than to discard the material world, and by that means expose philosophy to the ridicule of all men who will not offer up common sense as a sacrifice to metaphysics.
We ought, however, to do this justice both to the Bishop of Cloyne, and to the author of the Treatise of Human Nature, to acknowledge, that their conclusions are justly drawn from the doctrine of ideas, which has been so universally received. On the other hand, from the character of Bishop Berkeley, and of his predecessors Des Cartes, Locke, and Malefranche, we may venture to say, that if they had seen all the consequences of this doc- SECT. VIII.] OF TOUCH. 83 trine as clearly as the author before mentioned did, they would have suspected it vehemently, and examined it more carefully than they appear to have done.
The theory of ideas, like the Trojan horse, had a speci- ous appearance both of innocence and beauty; but if those philosophers had known that it carried in its belly death and destruction to all science and common sense, they would not have broken down their walls to give it admittance.
That we have clear and distinct conceptions of exten- sion, figure, motion, and other attributes of body, which are neither sensations nor like any sensation, is a fact of which we may be certain, as that we have sensations. And that all mankind have a fixed belief of an external material world, a belief which is neither got by reasoning nor education, and a belief which we cannot shake off, even when we seem to have strong arguments against it, and no shadow of argument for it, is likewise a fact, for which we have all the evidence that the nature of the thing admits. These facts are phenomena of human nature, from which we may justly argue against any hypo- thesis, however generally received. But to argue-from an hypothesis against facts is contrary to the rules of true philosophy.
OF THE HUMAN MIND.
OF THE HUMAN MIND.
CHAP. VI. OF SEEING.
SECT. I.
The Excellence and Dignity of this Faculty.
THE advances made in the knowledge of optics in the last age and in the present, and chiefly the discoveries of Sir Isaac Newton, do honour not to philosophy only, but to human nature. Such discoveries ought for ever to put to shame the ignoble attempts of our modern sceptics to depreciate the human understanding, and to dispirit men in the search of truth, by representing the human faculties as fit for nothing but to lead us into absurdities and contra- dictions.
Of the faculties called the Jive senses, sight is without doubt the noblest. The rays of light which minister to Ihis sense, and of which, without it, we could never have had the least conception, are the most wonderful and astonishing part of the inanimate creation. We must be satisfied of this, if we consider their extreme minuteness, their inconceivable velocity, the regular variety of colours which they exhibit, the invariable laws according to which they are acted upon by other bodies, in their reflections, inflections, and refractions, without the least change of their original properties, and the facility with which they pervade bodies of great density and of the closest texture, without resistance, without crowding or disturbing one another, without giving the least sensible impulse to the lightest bodies.
The structure of the eye, and of all its appurtenances, the admirable contrivances of nature for performing all its various external and internal motions, and the variety in SECT. I.] OF SEEING. 80 the eyes of different animals, suited to their several natures and ways of life, clearly demonstrate this organ to be a masterpiece of Nature's work. And he must be very ignorant of what hath been discovered about it, or have a \ i TV strange cast of understanding, who can seriously doubt, whether or not the rays of light and the eye were made for one another, with consummate wisdom, and per- fect skill in optics.
If we shall suppose an order of beings, endued with every human faculty but that of sight, how incredible would it appear to such beings, accustomed only to the -low information of touch, that, by the addition of an organ, consisting of a ball and socket of an inch diameter, they might be enabled, in an instant of time, without changing their place, to perceive the disposition of a whole army, or the order of a battle, the figure of a mag- nificent palace, or all the variety of a landscape? If a man were by feeling to find out the figure of the Peak of Teneriffe, or even of St. Peter's Church at Rome, it would be the work of a lifetime.
It would appear still more incredible to such beings as we have supposed, if they were informed of the disco- veries which may be made by this little organ in things far beyond the reach of any other sense: That by means of \\ we can find our way in the pathless ocean; that we can traverse the globe of the earth, determine its figure and dimensions, and delineate every region of it: yea, that we can measure the planetary orbs, and make disco- veries in the sphere of the fixed stars.
Would it not appear still more astonishing to such beings, if they should be farther informed, That, by means of this same organ, we can perceive the tempers and dis- positions, the passions and affections of our fellow crea- tures, even when they want most to conceal them? That when the tongue is taught most artfully to lie and dissem- ble, the hypocrisy should appear in the countenance to a discerning eye? A nd that by this organ we can often per- ceive what is straight and what is crooked in the mind as well as in the body? How many mysterious things must a 86 OF THE HUMAN MIND. [CHAP. VI.
blind man believe, if he will give credit to the relations of those that see? Surely he needs as strong a faith as is required of a good Christian.
It is not therefore without reason, that the faculty of seeing is looked upon, not only as more noble than the other senses, but as having something in it of a nature superior to sensation. The evidence of reason is called seeing, not feeling, smelling, or tasting. Yea, we are wont to express the manner of the divine knowledge by seeing, as that kind of knowledge which is most perfect iu us.
SECT. II.
Sight discovers almost Nothing which the Blind may not comprehend. The Reason of this.
NOTWITHSTANDING what hath been said of the dignity and superior nature of this faculty, it is worthy of our observation, that there is very little of the knowledge acquired by sight, that may not be communicated to a man born blind. One who never saw the light may be learned and knowing in every science, even in optics; and may make discoveries in every branch of philosophy. He may understand as much as another man, not only of the order, distances, and motions of the heavenly bodies, but of the nature of light, and of the laws of the reflection and refraction of its rays. He may understand distinctly, how those laws produce the phenomena of the rainbow, the prism, the camera obscura, and the magic lantern, and all the powers of the microscope and telescope. This is a fact sufficiently attested by experience.
In order to perceive the reason of it, we must distinguish the appearance that objects make to the eye, from the things suggested by that appearance: and again, in the visible appearance of objects, we must distinguish the appearance of colour from the appearance of extension, figure, and motion. First, then, as to the visible appear- SECT. II.] OF SEEING. 87 ance of the figure, and motion, and extension of bodies, I conceive that a man born blind may have a distinct notion, if not of the very things, at least of something extremely like to them. May not a blind man be made to conceive, that a body moving directly from the eye, or directly towards it, may appear to be at rest; and that the same motion may appear quicker or slower, according as it is nearer to the eye or farther off, more direct or more oblique? May he not be made to conceive that a plain surface, in a certain position, may appear as a straight line, and vary its visible figure as its position or the posi- tion of the eye is varied? That a circle seen obliquely will appear an ellipse: and a square, a rhombus or an oblong rectangle? Dr. Saunderson understood the projection of the sphere, and the common rules of perspective; and if he did, he must have understood all that I have mentioned. If there were any doubt of Dr. Saunderson's understand- ing these things, I could mention my having heard him say in conversation, that he found great difficulty in under- standing Dr. Halley's demonstration of that proposition, That the angles made by the circles of the sphere, are equal to the angles made by their representatives in the stereographic projection: But, said he, when I laid aside that demonstration, and considered the proposition in my own way, I saw clearly, that it must be true. Another gentleman, of undoubted credit and judgment in these matters, who had part in this conversation, remembers it distinctly.
As to the appearance of colour, a blind man must be more at a loss; because he hath no perception that resem- bles it. Yet he may, by a kind of analogy, in part sup- ply this defect. To those who see, a scarlet colour sig- nifies an unknown quality in bodies, that makes to the eye an appearance which they are well acquainted with, and have often observed: to a blind man, it signifies an un- known quality, that makes to the eye an appearance which he is unacquainted with. But he can conceive the eye to be variously affected by different colours, as the nose is by different smells, or the ear by different sounds. Thus he 88 OF THE HUMAN MIND. [CHAP. VI.
can conceive scarlet to differ from blue, as the sound of a trumpet does from that of a drum; or as the smell of aiv orange differs from that of an apple. It is impossible to know whether a scarlet colour has the same appearance to me which it hath to another man; and if the appearances of it to different persons differed as much as colour does from sound, they might never be able to discover this dif- ference. Hence it appears obvious, that a blind man might talk long about colours distinctly and pertinently: and if you were to examine him in the dark about the nature, composition, and beauty of them, he might be able to answer so as not to betray his defect.
We have seen how far a blind man may go in the know- ledge of the appearances which things make to the eye. As to the things which are suggested by them, or inferred from them, although he could never discover them of him- self, yet he may understand them perfectly by the infor- mation of others. And every thing of this kind that enters into our minds by the eye may enter into his by the ear. Thus, for instance, he could never, if left to the direction of his own faculties, have dreamed of any such thing as light; but he can be informed of every thing we know about it. He can conceive, as distinctly as we, the minuteness and velocity of its rays, their various degrees of refrangibility and reflexibility, and all the magical powers and virtues of that wonderful element. He could never of himself have found out, that there are such bodies as the sun, moon, and stars; but he may be informed of all the noble disco- veries of astronomers about their motions, and the laws of nature by which they are regulated. Thus it appears, that there is very little knowledge got by the eye, which may not be communicated by language to those who have no eyes.
If we should suppose, that it were as uncommon for men to see, as it is to be born blind; would not the few who had this rare gift appear as prophets and inspired teachers to the many? We conceive inspiration to give a man no new faculty, but to communicate to him in a new yray, and by extraordinary means, \vhat the faculties com- SECT. II.] OF SEEING. 89 raon to mankind can apprehend, and what he can commu- nicate to others by ordinary means. On the supposition we have made, sight would appear to the blind very simi- lar to this; for the few who had this gift would communi- cate the knowledge acquired by it to those who had it not. They could not indeed convey to the blind any distinct notion of the manner in which they acquired this know- ledge. A ball and socket would seem, to a blind man, in this case, as improper an instrument for acquiring such a variety and extent of knowledge as a dream or a vision. The manner iu which a man who sees discerns so many things by means of the eye is as unintelligible to the blind as the manner in which a man may be inspired with knowledge by the Almighty is to us. Ought the blind man, therefore, without examination, to treat all pretences to the gift of seeing as imposture? Might he not, if he were candid and tractable, find reasonable evidence of the reality of this gift in others, and draw great advantages from it to himself?
The distinction we have made between the visible ap- pearances of the objects of sight, and things suggested by them, is necessary to give us a just notion of the intention of nature in giving us eye.s. If we attend duly to the operation of our mind in the use of this faculty, we shall perceive, that the visible appearance of objects is hardly ever regarded by us. It is not at all made an object of thought or reflection, but serves only as a sign to intro- duce to the mind something else, which may be distinctly conceived by those who never saw.
Thus, the visible appearance of things in my room varies almost every hour, according as the day is clear or cloudy, as the sun is in the east, or south, or west, and as my eye is in one part of the room or in another: but I never think of these variations, otherwise than as signs of morning, noon, or night, of a clear or cloudy sky. A book or a chair has a different appearance to the eye, in every different distance or position; yet we conceive it to be still the same; and, overlooking the appearance, we immediately conceive the real figure, distance, and posi- 90 OF THE HUMAN MIND. [CHAP. VI.
tion of the body, of which its visible or perspective appear- ance is a sign and indication.
When I see a man at the distance of ten yards, and afterwards see him at the distance of a hundred yards, his visible appearance in its length, breadth, and all its linear proportions, is ten times less in the last case than it is in the first: yet I do not conceive him one inch diminished by this diminution of his visible figure. Nay, I do not in the least attend to this diminution, even when I draw from it the conclusion of his being at a greater distance. For such is the subtlety of the mind's operation in this case that we draw the conclusion without perceiving that ever the premises entered into the mind. A thousand such instances might be produced, in order to show that the visible appearances of objects are intended by nature only as signs or indications; and that the mind passes instantly to the things signified, without making the least reflection upon the sign, or even perceiving that there is any such thing. It is in a way somewhat similar, that the sounds of a language, after it is become familiar, are overlooked, and we attend only to the things signified by them.
It is therefore a just and important observation of the Bishop of Cloyne, That the visible appearance of objects is a kind of language used by nature, to inform us of their distance, magnitude, and figure. And this observation hath been very happily applied, by that ingenious writer, to the solution of some phenomena in optics which had before perplexed the greatest masters in that science. The same observation is further improved by the judicious Dr. Smith, in his optics, for explaining the apparent figure of the heavens, and the apparent distances and magnitudes of objects seen with glasses or by the naked eye.
Avoiding as much as possible the repetition of what hath been said by these excellent writers, we shall avail ourselves of the distinction between the signs that nature useth in this visual language, and the things signified by them; and, in what remains to be said of sight, shall first make some observations upon the signs.
OF SEEING. 91 SECT. III.
Of the Visible. Appearances of Objects.
IN this section we must speak of things which are never made the object of reflection, though almost every moment presented to the mind. Nature intended them only for signs; and in the whole course of life they are put to no other use. The mind has acquired a confirmed and in- veterate habit of inattention to them; for they no sooner appear than, quick as lightning, the thing signified suc- ceeds, and engrosses all our regard. They have no name in language; and although we are conscious of them when they pass through the mind, yet their passage is so quick and so familiar that it is absolutely unheeded; nor do they leave any footsteps of themselves, either in the me- mory or imagination. That this is the case with regard to the sensations of touch hath been shown in the last chap- ter; and it holds no less with regard to the visible ap- pearances of objects.
I cannot therefore entertain the hope of being intelli- gible to those readers who have not, by pains and practice, acquired the habit of distinguishing the appearance of objects to the eye, from the judgment which we form by sight, of their colour, distance, magnitude, and figure. The only profession in life wherein it is necessary to make this distinction is that of painting. The painter hath occasion for an abstraction, with regard to visible objects, somewhat similar to that which we here require: and this indeed is the most difficult part of his art. For it is evi- dent, that if he could fix in his imagination the visible appearance of objects, without confounding it with the things signified by that appearance, it would be as easy for him to paint from the life, and to give every figure its pro- per shading and relief, and its perspective proportions, as it is to paint from a copy. Perspective, shading, giving relief, and colouring, are nothing else but copying the appearance which things make to the eye. We may 02 OF THE HUMAN MIND. [CHAP. VI.
therefore borrow some light on the subject of visible ap- pearance from this art.
Let one look upon any familiar object, such as a book, at different distances and different positions: is he not able to affirm upon the testimony of his sight, that it is the same book, the same object, whether seen at the distance of one foot or of ten, whether in one position or another; that the colour is the same, the dimensions the same, and the figure the same, as far as the eye can judge? This surely must be acknowledged. The same individual ob- ject is presented to the mind, only placed at different dis- tances and in different positions. Let me ask, in the next place, Whether this object has the same appearance to the eye in these different distances? Infallibly it hath not, For, First, However certain our judgment may be, that the colour is the same, it is as certain that it hath not the same appearance at different distances. There is a cer- • tain degradation of the colour, and a certain confusion and indistinctness of the minute parts, which is the natural consequence of the removal of the object to a greater dis- tance. Those that are not painters or critics in painting- overlook this; and cannot easily be persuaded, that the colour of the same object hath a different appearance at the distance of one foot and of ten, in the shade and in the light. But the masters in painting know how, by the de- gradation of the colour and the confusion of the minute parts, figures, which are upon the same canvass and at the same distance from the eye, may be made to represent objects which are at the most unequal distances. They know how to make the objects appear to be of the same colour, by making their pictures really of different colours, according to their distances or shades.