is obvious. A deaf man in the company of those who hear, and a blind man with those who see, may live not uncomfortably: but, in order to judge of the value of a sense, we ought to consider what would be the consequence, if all mankind were to be deprived of it, or had never been endowed with it.

114. The eye is the organ of seeing, and its objects are light and colours. Bodies become visible by means of light, of which, in order to vision, some animals require more and others less, but all require some. The threefold signification of the word sight was formerly hinted at: it means the thing seen, the faculty of seeing, and the sensation or act of seeing. This last we may put an end to, by shutting our eyes; but the visible object exists, whether we see it or not; and the faculty of seeing remains in the mind when it is not exerted. No man imagines, that by shutting his eyes he annihilates light, or his power of seeing it; but every man knows, that by shutting his eyes he puts an end to the act of seeing, and renews it again when he opens them, When I say, my sight is weak, the noun denotes the power or faculty of seeing: when I say, I see a strange sight, the same word denotes the thing seen: and when I add, that I have a confused or indistinct sight of it, the word signifies the sensation or act of seeing. What is necessary to distinct vision must have been ex

plained to you in optics, and needs not be repeated

here.

115. Colours inhere not in the coloured body, but in the light that falls upon it: and a body presents to our eye that colour which predominates in the rays of light reflected by it: and different bodies reflect different sorts of rays, according to the texture and consistency of their minute parts. Now the component parts of bodies, and the rays of light, are not in the mind; and therefore colours, as well as bodies, are things external and the word colour denotes, always an external thing, and never a sensation in the mind.

116. The motion of the two eyes is nearly parallel; and yet the muscles that move the one are not connected with those that move the other. A picture of the visible object is formed in the retina of each eye; and yet the mind sees the object not double but single. The images in the retina are both inverted; and yet the object is seen, not inverted, but erect. These facts are by some writers so explained, as if we, at first, moved our eyes in different directions, and saw objects inverted and double; and afterwards, by the power of habit, came to see things as we now do, and to move our eyes as we now move them. But this theory is liable to unanswerable objections; for which my hearers are referred to the latter part of Dr. Reid's Inquiry into the human mind on the

principles of common sense. The motion of the eyes is parallel from the first; unless where there happens to be convulsion or disease. And it is probable, that, when an infant can with his eye take in all the parts of a visible object, he sees it, as we do, erect and single. Nor is it more strange, that the mind, by means of an inverted and double image, should see an object erect and single, than that it should perceive a visible thing by the intervention of an image, whereof it is not conscious, which is not known to the greater part of mankind, which can only be discovered by very nice experiments, and which was never heard of till Kepler found it out about the middle of the last century.

117. Every part of the body being an instrument of touch, we cannot pretend to enumerate the objects and organs of this sense. Heat and cold, hardness and softness, hunger and thirst, the pain of weariness, and the pleasure of rest, and, in a word, all bodily sensations, are referred to touch, except those of smell, taste, sound, colour, and light. In modern philosophy it has been made a question, whether distance, magnitude, and figure, be perceived by sight, by touch, or by both. The question belongs to optics; and the truth seems to be this: distance, magnitude, and figure, are originally perceived, not by sight, but by touch; but we learn to judge of them from the informations

of sight, by having observed, that certain visible appearances do always accompany and signify certain distances, magnitudes, and figures.

SECTION V.

Of Consciousness, or Reflection.

118. By this faculty we attend to and perceive what passes in our own minds. It is peculiar to rational beings, for the brutes seem to have nothing of it. In exerting it, the mind makes no use of any bodily organ, so far as we know. It is true, that the body and mind do mutually operate on each other; that certain bodily disorders hurt the mind; and that certain energies of the mind affect the body. This proves them to be intimately connected; but this does not prove, that any one bodily part is necessary to consciousness in the same manner as the eye, for example, is necessary to seeing.

119. Of the things perceived by this faculty, the chief is the mind itself. Every man is conscious, that he has within him a thinking active principle called a soul or mind. And this belief seems to be universal; so that if a man were to say, that he was not conscious of any such thing, the world would suspect him of either falsehood or insanity. Nay, the general acknowledgment of

the immortality of the soul, or of its existing after the dissolution of the body (an opinion which, in one form or other, is found in all nations), proves, that it is natural for mankind to consider the human soul and body as substances so distinct, that the former may live, and be happy or miserable, without the other.

120. Every man also believes, and holds himself to be absolutely certain, that, whatever changes his body may undergo in this life, his soul always continues one and the same. A temporary suspension of all our faculties may happen in deep sleep, or in a swoon; but we are certain, when we awake or recover, that we are the same persons we were before. In many things, both natural, as vegetable and animal bodies; and artificial, as ships and towns, the substance may be changed, and yet the thing be supposed to continue the same; because called by the same name; situated in the same place; applied to the same purpose; or having its parts so united, that, though new substance may have been added from time to time, or some of the old taken away, there never was any change of the whole substance made at once. But the human soul is always the same; its substance being incorporeal, as will be shewn hereafter, and consequently indivisible.

121. The things perceived by consciousness do as really exist, are as important, and may as well serve for the materials of science, as external