until the reinforcement arrived. Now these facts, I conceive to be decisive of the point at issue; and prove beyond all reasonable doubt, that the explanation above attempted of these phenomena, is correct. For here, we find that although the ideas must have passed in very quick succession through the mind of the officer above mentioned, yet a single circumstance, such as the anxious expectation of relief, fastening the attention painfully upon that object alone, was able to change the whole train of his perceptions, cause every less interesting thought to pass entirely unnoticed, while the mind was wholly engrossed by that single object, and thus make time appear long; although without the intervention of that circumstance it always appeared short. Thus it appears, that although many ideas may pass through the mind in a given time, yet where a few entirely engross its attention and deeply engage its hopes or fears, precisely the same effect is produced, as if but few ideas had passed through it; the less interesting being entirely unnoticed, and those which are more interesting completely engrossing it. The facts above stated, go to prove also, that although in the midst of a multitude of ideas passing through the mind, a few only may be noticed by it, so as to produce their usual effect; yet it will depend upon the nature of the object in immediate view of the mind, and the emotions which they excite, whether time shall appear long or short. When the officer was merely engaged, under ordinary circumstances in the heat of action, and a few great objects occupied his whole attention, time appeared short; but as soon as a circumstance that was painfully contemplated intervened, for instance, the anxious expectation of a reinforcement to relieve him from danger and difficulty; or in other words, a new principle of our nature was called into operation, that lengthened out the lapse of time, as does hope deferred, it then appeared long and tedious. Nothing more can be wanted to show the

correctness of the principles which we have above prescribed.

The two remaining ideas which Dr. Reid thinks cannot be traced back, either to sensation or reflection, are those which we have of substance, and of personal identity. His views in reference to the first, are thus expressed by him"It were to be wished that Mr. Locke, who inquired so accurately, and so laudably into the origin, certainty, and extent of human knowledge, had turned his attention more particularly to the origin of these two opinions, which he firmly believed; to wit, that sensible qualities must have a subject, which we call body, and that thought must have a subject, which we call mind. A due attention to these two opinions, which govern the belief of all men, even of sceptics, in the practice of life, would probably have led him to perceive, that sensation and consciousness, are not the only sources of human knowledge, and that there are principles of belief in human nature, of which we can give no account, but that they necessarily result from the constitution of our faculties; and that if it were in our power to throw off their influence upon our conduct and practice, we could neither speak nor act like reasonable men. We cannot give a reason, why we believe even our sensations to be real and not fallacious; why we believe what we are conscious of; why we trust any of our natural faculties, &c." Here we were led to conclude, in the first part of this paragraph, that we should meet with a sufficient argument to show, that sensation and consciousness, are not the only sources of human knowledge; but to our disappointment, we find it only asserted, what no one denies, that there are principles of belief in human nature, of which we can give no other account, but that they necessarily result from the constitution of our faculties. Had Mr. Locke attempted to assign a reason why, when we see figure and extension, we are irresistibly convinced that

there is something figured and extended, the strictures of the Dr. would justly have applied to him.

This he has not done, but in other parts of his works, places our belief in such cases upon the same ground as that assigned it by Dr. Reid, viz. the testimony of sense; and in this matter, he undertakes to trace to its origin, and ascertain our idea of substance, both that which is material, and that which is immaterial. The one he refers to sensation, and the other to reflection; and of that conception, in both cases, he gives the following account. All philosophers agree, that all that we know of things is from their properties. With the properties or qualities of matter, we become acquainted by sensation, as its hardness, softness, figure, colour, heat, cold, &c. and with the properties of mind by reflection, as of thinking, feeling, &c. Now we are assured, that where there are the qualities of figure, colour, extension, there must be something, coloured, figured, extended; and where there are the attributes of thought, willing, &c. there must be something capable of the exercise of these powers. As we cannot penetrate into the intimate essences of things, all the notion we can form of substance in either of the cases before mentioned, either of matter or mind, is, that it is the substratum or support of accidents or qualities. Thus all the idea we can have of substance is very obscure and inadequate, being able to consider it only as the essence or internal structure on which its properties depend. The schoolmen, indeed, speak of the substantial forms upon which the properties depend; but this is the mere idle use of a term without any distinct meaning annexed to it, and serves to explain nothing. It is true that the term support or substratum, still used in the schools, serves no better to give us a clear and distinct idea of substance; but it was not the purpose of Mr. Locke to convey any adequate perception of substance, for of this he knew the human mind was incapable, but merely to explain in what our idea of it consists. We

see, therefore, that in Dr. Reid's brief strictures upon Mr. Locke's doctrine upon this point, he has confounded two things entirely distinct from each other, the ascertaining of our idea of substance, and an attempt to explain the ground of our belief, that any substances exist. How are we to repose confidence in the sentiments of an author who, in a matter so plain, so egregiously misapprehends his subject?

The last particular which he enumerates as forming an exception to the doctrine of Mr. Locke, that all our simple ideas are derived from sensation and reflection, is that of personal identity. As, however, he has no where distinctly stated the ground on which the opinion rests, that our idea of personal identity cannot be traced back either to the one or the other assigned inlets of human knowledge, but has rather confined his strictures to the general principles of Mr. Locke; and as, moreover, the same method of reasoning, by which we have answered his other objections, would be applicable in this case, we shall follow him in this course, and simply indulge ourselves in a few observations upon the subject of identity, and personal identity. Mr. Locke, in his entertaining disquisition upon this subject, has said many excellent things, and his opinions are unobjectionable, except on the topic of personal identity; and it is remarkable, that upon this also, while he exhibits another proof of the liabili ty even of the greatest and most exalted geniuses, to occasional failures in their attempts at the investigation of nature, and has failed in attaining to the truth himself, by his luminous exposition of the subject, he has diffused so clear a light around it, as to render it easily perceptible to his readers.

The object of inquiry in the schools was to ascertain the principium individuationis, or principle of identity, and as Bishop Butler has remarked, (who in a short treatise on this subject has detected the slight inaccuracy of Mr. Locke, and at the same time placed it in so clear a point of view, as to preclude the possibility of any rational controversy concern

ing it in future,) they might as well have inquired about the principle of equality or similitude, or any other of our simple perceptions. We all understand as perfectly what is meant by identity, as by the equality or similitude of two objects; and as it is a simple idea, it is not susceptible of definition. "Now when it is asked," says Bishop Butler, in that lucid dissertation affixed to his analogy of natural and revealed religion; "when it is asked, wherein personal identity consists, the answer should be the same, as if it were asked, wherein consists similitude or equality; that all attempts to define, would but perplex it. Yet there is no difficulty at all in ascertaining the idea. For as upon two triangles being compared or viewed together, there arises to the mind the idea of similitude; or upon twice two and four, the idea of equality; so likewise upon comparing the consciousnesses of one's self, or one's own existence in any two moments, there as immediately arises to the mind the idea of personal identity. And as the two former comparisons not only give us the ideas of similitude and equality, but also show us that two triangles are alike, and twice two and four are equal; so the latter comparison, not only gives us the idea of personal identity, but also shows us the identity of ourselves in these two moments; the present, suppose, and that immediately past; or the present, and that a month, a year or twenty years past."

This is a very profound and just observation, and serves completely to unravel the whole mystery. All that is left us, therefore, in such cases, is merely to ascertain our ideas of identity as the term is applicable to different objects, without attempting the fruitless inquiry in what identity itself consists. As it is a relative idea, it will assume a different meaning, according to the nature of the things spoken of, and the objects which are compared. When we speak, for instance, of the identity of a mass or congeries of matter, of a plant, a man, or a person, we express different shades of the same