occasion considerable pain: then nature calls upon us to attend to it; and then we acknowledge that it is a mere sensation,and can only be in a sentient being. If a man runs his head with violence against a pillar, I appeal to him whether the pain he feels resembles the hardness of the stone; or if he can conceive any thing like what he feels to be in an inanimate piece of matter.

"The attention of the mind is here entirely turned toward the painful feeling; and, to speak in the common language of mankind, he feels nothing in the stone, but feels a violent pain in his head. It is quite otherwise when he leans his head gently against the pillar; for then he will tell you that he feels nothing in his head, but feels hardness in the stone. Hath he not a sensation in this case as well as in the other? Undoubtedly he hath ; but it is a sensation which nature intended only as a sign of something in the stone; and, accordingly, he instantly fixes his attention upon the thing signified; and cannot, without great difficulty, attend so much to the sensation as to be persuaded that there is any such thing distinct from the hardness it signifies.

"But however difficult it may be to attend to this fugitive sensation, to stop its rapid progress, and to disjoin it from the external quality and hardness, in whose shadow it is apt immediately to hide itself: this is what a philosopher by pains and practice must attain, otherwise it will be impossible for him to reason justly upon this subject, or even to understand what is here advanced. For the last appeal, in subjects of this nature, must be to what a man feels or perceives in his own mind."

§. 170. Of certain indefinite feelings sometimes ascribed

to the touch.

In connection with these views on the sensations of touch, it is proper to remark, that certain feelings have been ascribed to that sense, which are probably of a character too indefinite, to admit of a positive and undoubted classification. Although they clearly have their

place, in the general arrangement which has been laid down, with the states of mind which we are now considering; that is to say, are rather of an external and material, than of an internal origin; still they do not so evidently admit of an assignment to a particular sense. Those sensations to which we now refer, (if it be proper to use the term in application to them,) appear to have their origin in the human system considered as a whole, made up of bones, flesh, muscles, the senses, &c. rather than to be susceptible of being traced to any particular part. Of this description are the feelings expressed by the terms, uneasiness, weariness, weakness, sickness, and those of an opposite character, as ease, hilarity, health, vigour, &c.

Similar views will be found to apply, in part at least, to the sensations, which we express by the terms HUNGER and THIRST. These appear to be complex in their nature, including a feeling of uneasiness, combined with a desire. to relieve that uneasiness. When we say that these views will apply in part to hunger and thirst, the design is to limit the application of them to the element of uneasiness. This elementary feeling undoubtedly has its origin in the bodily system, and therefore comes in this case under the general class of notions of an EXTERNAL origin; but still it is not easy to say, that it should be arranged with our tactual feelings, which has sometimes been done. Every one must be conscious, it is thought, that the feeling of hunger does not greatly resemble the sensations of hardness and softness, roughness or smoothness or other sensations, which are usually ascribed to the touch.-The cause of that peculiar state of the nerves of the stomach, which is antecedent to the uneasy feeling, involved in what is termed hunger, has been a subject of difference of opinion, and does not appear to be well understood. If we were fully acquainted with this, we might perhaps be less at a loss where to arrange the feeling in question.

§. 171. Relation between the sensation and what is outwardly signified.

We here return a moment to the subject of the relation between the internal sensation and the outward object; and again repeat, that the mental state and the corresponding outward object are altogether diverse. This view holds good in the case of the secondary, as well as of the primary qualities of matter. Whether we speak of extension or resistance, or heat, or colour, or roughness, there are in all cases alike, two things, the internal affection and the outward quality; but they are utterly distinct, totally without likeness to each other. But how it happens that one thing, which is totally different from another, can nevertheless give us a knowledge of that, from which it differs, it would be a waste of time to attempt to explain. Our knowledge is undoubtedly limi

ted to the mere fact.

This is one of those difficult, but decisive points in MENTAL PHILOSOPHY, of which it is essential to possess a precise and correct understanding. The letters, which cover over the page of a book, ale a very different thing from the thought, and the combinations of thought, which they stand for. The accountant's columns of numerals are not identical with the quantities and their relations, which they represent. And so in regard to the mind; all its acts are of one kind, and what they stand for is of another. The mind, in all its feelings and operations, is governed by its own laws, and characterizes its efforts by the essential elements of its own nature. Nothing, which is seen or heard, nothing which is the subject of taste or touch or any other sense, nothing material, which can be imagined to exist in any place or in any form, can furnish the least positive disclosure either of its intrinisic nature or of the mode of its action.

What then is the relation between the sensation and the outward object, between the perception and the thing perceived? Evidently that of the sign and the thing signified. And as in a multitude of cases, the sign may

give a knowledge of its object without any other grounds of such knowledge than mere institution or appointment, so it is in this. The mind, maintaining its appropriate action, and utterly rejecting the intervention of all images and visible representations, except what are outward and material and totally distinct from itself both in place and nature, is notwithstanding susceptible of the knowledge of things exteriour, and can form an acquaintance with the universe of matter.

A misapprehension in this respect, the mistaken supposition of the mind's either receiving actual filmy images from external objects, or being itself transformed into the likeness of such images, has been in times past the source of much confusion and contention. But that opinion, however prevalent it may have been once, is mere hypothesis; it has not the slightest well-founded evidence in its favour. Still we can reject it wholly from our belief, and from all influence on our belief, only by guarding against early associations, by a rigid self-inspection, and by carefully separating the material and the immaterial, the qualities of mind and of matter.

CHAPTER SIXTH.

THE SENSE OF SIGHT.

§. 172. Of the organ of sight and the uses or benefits of

that sense.

Of those instruments of external perception, with which a benevolent Providence has favoured us, a high rank must be given to the sense of seeing. If we were restricted in the process of acquiring knowledge to the informations of the touch merely, how many embarrassments would attend our progress, and how slow it would prove! Having ever possessed sight, it would be many years before the most acute and active person could form an idea of a mountain or even of a large edifice. But by the additional help of the sense of seeing, he not only observes the figure of large buildings, but is in a moment possessed of all the beauties of a wide and variegated landscape.

The organ of this sense is the eye. On a slight examination the eye is found to be a sort of telescope, having its distinct parts, and discovering throughout the most exquisite construction. The medium, on which this organ acts, are rays of light, every-where diffused, and always advancing, if they meet with no opposition, in direct lines. The eye like all the other senses not only receives externally the medium, on which it acts; but carries the rays of light into itself; and on principles purely scientific refracts and combines them anew.

It does not however fall within our plan to give a mi