vigorous they might happen to be. By a proper distribution of these documents, and a judicious reference of them to a few general titles, a very ordinary Memory is enabled to accomplish more, than the most retentive, unassisted by method. We know, with certainty, where to find any article we may have occasion for, if it be in our possession; and the search is confined within reasonable limits, instead of being allowed to wander at random amidst a chaos of particulars.

Or, to take an instance still more immediately applicable to our purpose; suppose that a man of letters were to record, in a commonplace-book, without any method, all the various ideas and facts which occurred to him in the course of his studies; what difficulties would he perpetually experience in applying his acquisitions to use? and how completely and easily might these difficulties be obviated by referring the particulars of his Information to certain general heads? It is obvious, too, that, by doing so, he would not only have his knowledge much more completely under his command, but as the particulars classed together would all have some connection, more or less, with each other, he would be enabled to trace, with advantage, those mutual relations among his ideas, which it is the object of philosophy to ascertain.

A commonplace-book, conducted without any method, is an exact picture of the Memory of a man whose inquiries are not directed by philosophy. And the advantages of order in treasuring up our ideas in the mind, are perfectly analogous to its effects when they are recorded in writing.

Nor is this all. In order to retain our knowledge distinctly and permanently, it is necessary that we should frequently recall it to our recollection. But how can this be done without the aid of arrangement? Or supposing that it were possible, how much time and labor would be necessary for bringing under our review the various particulars of which our information is composed? In proportion as it is properly systematized, this time and labor are abridged. The mind dwells habitually, not on detached facts, but on a comparatively small number of general principles; and, by means of these, it can summon up, as

occasions may require, an infinite number of particulars associated with them; each of which, considered as a solitary truth, would have been as burdensome to the Memory, as the general principle with which it is connected.*

Classification alone does not constitute philosophy.—I would not wish it to be understood from these observations, that philosophy consists in classification alone; and that its only use is to assist the Memory. I have often, indeed, heard this asserted in general terms; but it rather appears to me to be obvious, that, although this be one of its most important uses, yet something more is necessary to complete the definition of it. Were the case otherwise, it would follow, that all classifications are equally philosophical, provided they are equally comprehensive. The very great importance of this subject will, I hope, be a sufficient apology for me, in taking this opportunity to correct some mistaken opinions which have been formed concerning it.

IV. Aid which the Memory derives from philosophical arrangement. - It was before observed, that the great use of the faculty of Memory, is to enable us to treasure up, for the future regulation of our conduct, the results of our past experience, and of our past reflections. But in every case in which we judge of the future from the past, we must proceed on the belief, that there is, in the course of events, a certain degree, at least, of uniformity. And, accordingly, this belief is not only justified by experience, but (as Dr. Reid has shown, in a very satisfactory manner,) it forms a part of the original constitution of the human mind. In the general laws of the material world, this uniformity is found to be complete; insomuch that, in the

*It is very justly and ingeniously remarked by Dr. Priestley, that "the more we know of any branch of science, the less is the compass into which we are able to bring its principles, provided the facts from which they are inferred be numerous." The reason is, that, "in an advanced state of knowledge, we are able to reduce more of the particular into general observations; whereas, in the infancy of a science, every observation is an independent fact; and, in delivering the principles of it, they must all be distinctly mentioned; so that, though a selection may be made, a proper abridgment is impossible."

same combinations of circumstances, we expect, with the most perfect assurance, that the same results will take place. In the moral world, the course of events does not appear to be equally regular; but still it is regular to so great a degree, as to afford us many rules of importance in the conduct of life.

A knowledge of nature, in so far as it is absolutely necessary for the preservation of our animal existence, is obtruded on us, without any reflection on our part, from our earliest infancy. It is thus that children learn of themselves to accommodate their conduct to the established laws of the material world. In doing so, they are guided merely by Memory, and the instinctive principle of anticipation which has just been mentioned.

There are, however, two im

In forming conclusions concerning future events, the philosopher, as well as the infant, can only build with safety on past experience; and he, too, as well as the infant, proceeds on an instinctive belief, for which he is unable to account, of the uniformity of the laws of nature. portant respects, which distinguish the knowledge he possesses from that of ordinary men. In the first place, it is far more extensive, in consequence of the assistance which science gives to his natural powers of invention and discovery. Secondly, it is not only more easily retained in the Memory, and more conveniently applied to use, in consequence of the manner in which his ideas are arranged; but it enables him to ascertain, by a process of reasoning, all those truths which may be synthetically deduced from his general principles. The illustration of these particulars will lead to some useful remarks; and will at the same time show, that, in discussing the subject of this section, I have not lost sight of the inquiry which occasioned it.

How philosophy aids our powers of invention and discovery.— I. (1.) It was already remarked, that the natural powers of Memory, together with that instinctive anticipation of the future from the past, which forms one of the original principles of the mind, are sufficient to enable infants, after a very short experience, to preserve their animal existence. The laws of nature, which it is not so important for us to know, and which are the objects of philosophical curiosity, are not so obviously exposed

to our view, but are, in general, brought to light by means of experiments which are made for the purpose of discovery; or, in other words, by artificial combinations of circumstances, which we have no opportunity of seeing conjoined in the course of our ordinary experience. In this manner, it is evident, that many connections may be ascertained, which would never have occurred spontaneously to our observation.

(2.) There are, too, some instances, particularly in the case of the astronomical phenomena, in which events, that appear to common observers to be altogether anomalous, are found, upon a more accurate and continued examination of them, to be subjected to a regular law. Such are those phenomena in the heavens, which we are able to predict by means of cycles. In the cases formerly described, our knowledge of nature is extended by placing her in new situations. In these cases, it is extended by continuing our observations beyond the limits of ordinary curiosity.

(3.) In the case of human affairs, as long as we confine our attention to particulars, we do not observe the same uniformity, as in the phenomena of the material world. When, however, we extend our views to events which depend on a combination of different circumstances, such a degree of uniformity appears, as enables us to establish general rules, from which probable conjectures may often be formed with respect to futurity. It is thus, that we can pronounce, with much greater confidence, concerning the proportion of deaths which shall happen in a certain period among a given number of men, than we can predict the death of any individual; and that it is more reasonable to employ our sagacity, in speculating concerning the probable determinations of a numerous society, than concerning events which depend on the will of a single person.

In what manner this uniformity in events depending on contingent circumstances is produced, I shall not inquire at present. The advantages which we derive from it are obvious, as it enables us to collect, from our past experience, many general rules, both with respect to the history of political societies, and the characters and conduct of men in private life.

(4.) In the last place, the knowledge of the philosopher is more extensive than that of other men, in consequence of the attention which he gives, not merely to objects and events, but to the relations which different objects and different events bear to each other.

The observations and the experience of the vulgar are almost wholly limited to things perceived by the senses. A similarity between different objects, or between different events, rouses their curiosity, and leads them to classification and to general rules. But a similarity between different relations is seldom to be traced without previous habits of philosophical inquiry. Many such similarities or connections, however, are to be found in nature; and when once they are ascertained, they frequently lead to important discoveries; not only with respect to other relations, but with respect to the objects or to the events which are related. These remarks it will be necessary to illustrate more particularly.

Aid derived from a study of the relations of things. The great object of geometry is to ascertain the relations which exist between different quantities, and the connections which exist between different relations. When we demonstrate, that the angle at the centre of a circle is double of the angle at the circumference on the same base, we ascertain a relation between two quantities. When we demonstrate, that triangles of the same altitude are to each other as their bases, we ascertain a connection between two relations. It is obvious, how much the mathematical sciences must contribute to enlarge our knowledge of the universe, in consequence of such discoveries. In that simplest of all processes of practical geometry, which teaches us to measure the height of an accessible tower, by comparing the length of its shadow with that of a staff fixed vertically in the ground, we proceed on the principle, that the relation between the shadow of the staff and the height of the staff is the same with the relation between the shadow of the tower and the height of the tower. But the former relation we can ascertain by actual measurement; and, of consequence, we not only obtain the other relation, but, as we can measure one of