other words, we conclude with confidence that when we observe the first of two such events, the second will follow; and that when we observe the second, the first has preceded it. The first we call cause, the second effect. Thus our general confidence in the uniformity of the true relations or sequences of events is an original or instinctive principle, and not the result of experience; but it is by experience that we ascertain what the individual sequences are which observe this uniformity, or, in other words, learn to distinguish connections which consist of incidental contiguity from those which constitute true and uniform relations.

The natural tendency of the mind appears indeed to be to infer causation from every succession of phenomena and to expect uniformity in every sequence. It is from experience we learn that this impression is not to be relied on in regard to individual sequences, but requires to be corrected by observation. The result of our further experience then is to ascertain what those sequences or connections are which are uniform, and which, consequently, we may consider as connected in the manner of causation. We are thus first taught by experience the caution which is necessary in considering events as connected in the manner of cause and effect, and learn not to assume this relation till, by further experience, we have ascertained that the sequence is uniform. This caution, however, has no reference to our instinctive impression of causation, or our absolute conviction that every event must have an adequate cause; it only relates to our fixing the arrangement of individual antecedents, or, in other words, to our determining what individual events we are warranted in considering as the true antecedents or causes of certain other events. This, accordingly, can in many cases be accomplished only by long and extensive observation; while, in others, a single instance may be sufficient to produce an absolute conviction of what is the true antecedent. A child who has been only once burnt may dread the fire as certainly as if the accident had happened a hundred times; and there are many other instances in which the conviction may be produced in the same rapid manner. The natural tendency of the mind, in fact, is not only to infer the connection, but in many cases to carry it further than the truth. If, for instance, we suppose a man who, for the first time in his life, has seen gunpowder explode upon a match being applied to it, he would probably have an immediate conviction that a similar explosion would take place again in similar

circumstances. But he would perhaps go further than this: he would probably expect a similar explosion when he applied a match to other black powders, with the nature of which he was unacquainted, such as powdered charcoal. It is by experience that this erroneous expectation would be corrected, and that he would learn the precise instances in which the particular result takes place. But it is also by experience that he learns the former, though the conviction was produced more immediately; for there is nothing in the character of gunpowder and charcoal from which any man could pronounce, by reasoning à priori, that the one would explode with violence when a match was applied to it and the other remain entirely unchanged.

Thus, our general impression of causation is not the result of experience, but an original and intuitive principle of belief; that is, our absolute conviction that every event must have an adequate cause. This is, in fact, that great and fundamental truth by which, from the properties of a known effect, we infer the powers and qualities of an unknown cause. It is in this manner, for example, that from the works of nature we infer the existence and the attributes of the Almighty Creator. But in judging of the connection between any two individual events in that order of things which he has established, our idea of causation is derived from experience alone; for, in regard to any two such events, our idea of causation or of power amounts to nothing more than our knowledge of the fact that the one is invariably the antecedent of the other. Of the mysterious agency on which the connection depends, we know nothing, and never can know anything in our present state of being. We know that the application of a match always sets fire to gunpowder, and we say that it has the power of doing so, or that it is the cause of the explosion; but we have not the least conception why the application of fire produces combustion in an inflammable substance; - these expressions, therefore, amount to nothing more than a statement of the fact that the result is universal.

When we speak, therefore, of physical causes, in regard to any of the phenomena of nature, we mean nothing more than the fact of a certain uniform connection which has been observed between events. Of efficient causes, or the manner in which the result takes place, we know nothing. In this sense, indeed, we may be said not to know the cause of anything, even of events which at first sight appear the most simple and obvious. Thus,

the communication of motion from one body to another by im. pulse appears a very simple phenomenon,- but how little idea have we of the cause of it! We say the bodies touch each other, and so the motion is communicated. But, in the first place, we cannot say why a body in motion, coming in contact with one at rest, should put the latter in motion; and, further, we know that they do not come in contact. We may consider it, indeed, as ascertained that there is no such thing as the actual contact of bodies under these circumstances; and therefore the fact which appears so simple comes to be as unaccountable as any phenomenon in nature. What, again, appears more intelligible than an unsupported body falling to the ground? Yet what is more inexplicable than that one mass of matter should thus act upon another, at any distance, and even though a vacuum be inter posed between them? The same observation will be seen to apply to all the facts which are most familiar to us. Why, for example, one medicine acts upon the stomach, another on the bowels, a third on the kidneys, a fourth on the skin, we have not the smallest conception; we know only the uniformity of the facts.

It is of importance to keep in mind the distinction now referred to between physical and efficient causes, as the former only are the proper objects of philosophical inquiry. The term final cause, again, has been applied to a subject entirely different; namely, to the appearances of unity of design in the phenomena of nature, and the manner in which means are adapted to particular ends. The subject is one of great and extensive importance, but it appears desirable that the name be altered, though it is sanctioned by high authority; for, when viewed in connection with the sense in which the word cause is employed in modern science, it expresses a meaning remarkably different. The investigation to which it refers is also of a distinct nature, though one of the highest interest. It leads us chiefly to the inductions of natural religion respecting a great and intelligent First Cause; but it may also be directed to the discovery of truth in regard to the phenomena of nature. One of the most remarkable examples of this last application of it is to be found in the manner in which Harvey was led to the discovery of the circulation of the blood, by observing the valves in the veins, and contemplating the uses to which their peculiar structure might be adapted.

The object of all science is to ascertain these established relations of things, or the tendency of certain events to be uniformly followed by certain other events; in other words, the aptitude of certain bodies to produce or to be followed by certain changes in other bodies in particular circumstances. The object

of art is to avail ourselves of the knowledge thus acquired, by bringing bodies into such circumstances as are calculated to lead to those actions upon each other of which we have ascertained them to be capable. Art, therefore, or the production of certain results by the action of bodies upon each other, must be founded upon science, or a knowledge of their fixed and uniform relations and tendencies. This principle applies to all sciences, and to the arts or practical rules which are founded upon them; and the various sciences differ only in the particular substances or events which are their more immediate objects.

In the physical sciences, we investigate the relations of material substances, and their actions upon each other, either of a mechanical or chemical nature. On the relations thus ascertained are founded the mechanical and chemical arts, in which we produce certain results by bringing bodies into such circumstances as are calculated to give rise to their peculiar actions. But mental phenomena have also their relations, which are likewise fixed and uniform; though it may be more difficult to ascertain the truth in regard to them than in the relations of material things.

The relations or sequences of mental phenomena are to be considered in two points of view; namely, relations to each other, and relations to external things. In regard to both, it seems necessary to divide the phenomena themselves into three classes:

1. Simple intellect, or those powers by which we perceive, remember, and combine facts or events, and compare them with each other: such as perception, memory, imagination, and judgment.

2. Passive emotions, or those by which the mind is affected by certain pleasurable or painful feelings, which are, or may be, confined entirely to the individual who is the subject of them.

3. Active emotions, or those which tend directly to influence the conduct of men, either as moral and responsible beings, or as members of society.

In all these classes mental phenomena have certain relations to each other and to external things, the investigation of which is the object of particular branches of science; and these lead to certain arts or practical rules which are founded upon them

Intellectual science investigates the laws and relations of the processes of simple intellect, as perception, memory, imagination, and judgment; and the proper cultivation and regulation of these is the object of the practical art of intellectual education.

The passive emotions may be influenced or excited in two ways; namely, through our relations to other sentient and intelligent beings, and by material or inanimate things. To the former head are referable many of the tenderest and most interesting feelings of our nature, as love, hope, joy, and sorrow. To the latter belong those emotions which come under the subject of taste, or the tendencies of certain combinations of material things to excite emotions of a pleasurable or painful kind, as our impressions of the sublime, the beautiful, the terrible, or the ludicrous. The practical rules or processes connected with the science of the passive emotions arrange themselves into two classes, corresponding to the two divisions now mentioned. To the former belong the regulation of the emotions, and all those rules of conduct not exactly referable to the higher subject of morals, which bear an extensive influence on the ties of friendship-and the relations of social and domestic intercourse. To the latter belong chiefly those processes which come under the head of the fine arts; namely, the arts of the painter, the sculptor, the architect, the musician, perhaps we may add, the poet and the dramatist.

The active emotions, or those which influence human conduct, are referable to two classes; namely, those which affect men individually as moral and responsible agents, and those which affect them as united in large bodies constituting civil society. The cultivation of the emotions of the former class, and the investigation of the motives and principles by which they are influenced, belong to the high subjects of morals and religion. The investigation and control of emotions of the latter class come under the science of politics; and the practical art, founded upon it, relates to those measures by which the statesman attempts to control and regulate the conduct of masses of mankind united as members of a great civil community.

In medical science the objects of our researches are chiefly the relations between external things and the living powers of animal bodies,- and the relations of these powers to each other; -more particularly in regard to the tendencies of external things to produce certain changes upon living bodies, either as causes of disease or as remedies. The practical art founded upon this