The transactions between authors and booksellers are seldom accompanied by any formidable array of legal formalities; but Hume and his publishers seem to have thought it necessary to bind each other in the most stringent manner, to the performance of their respective obligations, by "articles of agreement, made, concluded, and agreed, upon the 26th day of September, in the year of our Lord one thousand seven hundred and thirty-eight, and in the twelfth year of the reign of our sovereign lord King George the Second,—between David Hume of Lancaster Court of the one part, and John Noone of Cheapside, London, bookseller, of the other part." By this very precise document, it is provided, that "the said David Hume shall and will permit and suffer the said John Noone to have, hold, and enjoy, the sole property, benefit, and advantage of printing and publishing the first edition of the said book, not exceeding one thousand copies thereof." The author, in return, receives £50, and twelve bound copies of the book.[66:1] The transaction is on the whole creditable to the discernment and liberality of Mr. Noone. It may be questioned, whether, in this age, when knowledge has spread so much wider, and money is so much less valuable, it would be easy to find a bookseller, who, on the ground of its internal merits, would give £50 for an edition of a new metaphysical work, by an unknown and young author, born and brought up in a remote part of the empire. These articles refer to the first and second of the three volumes of the "Treatise of Human Nature;" and they were accordingly published in January, 1739. They include "Book I. Of the Understanding," and "Book II. Of the Passions."

It has been generally and justly remarked, that the Treatise is among the least systematic of philosophical works—that it has neither a definite and comprehensive plan, nor a logical arrangement. It was, indeed, so utterly deficient in the former—there was so complete a want of any projected scope of subject which the author was bound to exhaust in what he wrote—that an attempt to divide and subdivide the matter after it had been written, according to a logical arrangement, would only, as a sort of experimentum crucis, have exposed the imperfect character of the original plan. The author, therefore, very discreetly allowed his matter to be arranged as the subjects of which he treated had respectively suggested themselves, and bestowed on his work a title rather general than comprehensive,—a title, of which all that can be said of its aptness to the subject is, that no part of his book can be said to be wholly without it, while he might have included an almost incalculable multitude of other subjects within it. He called it simply "A Treatise of Human Nature;" and by a subsidiary title, explanatory rather of his method than definitive of his matter, he called it "an attempt to introduce the experimental method of reasoning into moral subjects."

The purely metaphysical,[67:1] and, at the same time, the most original portion of the work, and that which has most conspicuously rendered itself a constituent part of the literature of intellectual philosophy, is "Book I. Of the Understanding." "Book II. Of the Passions," contains mixed metaphysics and ethics, with occasional notices of phenomena, which, though Hume does not, other writers would be likely to connect with physiological inquiries. The third book, "Of Virtue and Vice in General," published a year later, is of an ethical character, being an inquiry into the origin and proper system of morals, and an application of the system to government and politics.

The "Treatise of Human Nature" afforded materials for the criticism of two very distinct classes of writers. The one consisted of men imbued with a spirit of inquiry kindred to that of Hume, and a genius capable of appreciating his services in the cause of truth; who, as the teachers of systems of which they were themselves the architects, had to attack or to defend the principles promulgated in the Treatise, according as these differed from or corresponded with their own. It is in the writings of these men that the true immortality of Hume as a philosopher consists. Whether they find in him great truths to acknowledge, or subtle and plausible errors to attack, they are the vital evidence of the originality of his work, of the genius that inspired it, and of its great influence on human thought and action. The other class of critics are those who, in pamphlets, or works more ambitious but not rising in real solidity above that fugitive class, or in occasional digressions from other topics, have endeavoured to prejudice the minds of their readers against the principles of the Treatise, by exaggeration, or by the misapplication of their metaphysical doctrines to the proceedings of every-day life,—a set of literary efforts of quick production and as quick decay.

To the former class of authors, it is of course not within the scope of the present writer's ambition to belong, and he sees no occasion to attempt to imitate the latter. In a work, however, which professes to give a life of David Hume, it is necessary to say something about the "Treatise of Human Nature;" and as a preliminary to such an attempt, it may be well to mark the boundaries within which the writer conceives that the duty he has assumed calls on him for a description of the work, neither impugning nor defending any of the opinions it sets forth.

It seems to be right that some attempt should be made to describe the character and strength of the author's intellect, and the method of its operations; and to give a view of the fundamental characteristic principles by which he professes to distinguish his own philosophy from that of other writers on metaphysical subjects. An attempt should also be made to tell in what respect Hume has made incidental suggestions which have either been admitted as new truths in metaphysics, or have, as original but perhaps fallacious suggestions, afforded to other thinkers the means of establishing truths. These being the general objects to be kept in view, there is no intention to take them in any precise order, or to exhaust them in remarks on this one work. To attempt an analysis of the work would be out of place. There can be no more repulsive matter for reading than condensed metaphysics; and probably there is nothing less instructive than those abridgments, which, necessarily suppressing the author's discursive arguments, appeal almost entirely to the memory. To seize on and give a descriptive rather than an analytical account of the prominent features of the system, will be the chief aim of these remarks. Moreover, the Treatise bears on subjects which are nearly all recalled in its author's subsequent works; and while there are some things in the critical history of Hume's opinions which may be appropriately viewed in connexion with his first publication, there are others which it may be more expedient to examine when he is found reconsidering the subjects in his later works; and again, others which may be viewed in a general attempt to describe the extent of his literary achievements.

The Treatise has been already spoken of as embracing two great objects, metaphysics and ethics; or three, if politics be considered as distinct from ethics. The great leading principle of the metaphysical department, and a principle which is never lost sight of in any part of the book, is, that the materials on which intellect works are the impressions which represent immediate sensation, whether externally as by the senses, or internally as by the passions, and ideas which are the faint reflections of these impressions. Thus to speak colloquially, when I see a picture, or when I am angry with some one, there is an impression; but when I think about this picture in its absence, or call to recollection my subsided anger, what exists in either case is an idea. Hume looked from words to that which they signified, and he found that where they signified any thing, it must be found among the things that either are or have been impressions. The whole varied and complex system of intellectual machinery he found occupied in the representation, the combination, or the arrangement of these raw materials of intellectual matter. If I say I see an object, I give expression to the fact, that a certain impression is made on the retina of my eye. If I convey to the person I am speaking to an accurate notion of what I mean, I awaken in his mind ideas left there by previous impressions, brought thither by his sense of sight.[70:1] Thus, in the particular case of the external senses, when they are considered as in direct communication between the mind and any object, there are impressions: when the senses are not said to be in communication with the object, the operations of the mind in connexion with it, are from vestiges which the impressions have left on the mind; and these vestiges are called ideas, and are always more faint than the original impressions themselves. And a material circumstance to be kept in view at the very threshold of the system is, that there is no specific and distinct line drawn between impressions and ideas. Their difference is in degree merely—the former are stronger, the latter weaker. There is no difference in kind; and there is sometimes doubt whether that which is supposed to be an impression may not be a vivid idea, and that which is supposed to be an idea a faint impression.

When Hume examined, with more and more minuteness, the elements of the materials on which the mind works, he could still find nothing but these impressions and ideas. Looking at language as a machinery for giving expression to thought, he thus established for himself a test of its adaptation to its right use,—a test for discovering whether in any given case it really served the purpose of language, or was a mere unmeaning sound. As he found that there was nothing on which thought could operate but the impressions received through sensation, or the ideas left by them, he considered that a word which had not a meaning to be found in either of these things, had no meaning at all. He looked upon ideas as the goods with which the mind was stored; and on these stores, as being of the character of impressions, while they were in the state of coming into the mind. When any one, then, in reasoning, or any other kind of literature, spoke of any thing as existing, the principle of his theory was, that this storehouse of idealized impressions should be searched for one corresponding to the term made use of. If such an impression were not found, the word was, so far as our human faculties were concerned, an unmeaning one. Whether there was any existence corresponding to its meaning, no one could say: all that the sceptical philosopher could decide was, that, so far as human intellect was put in possession of materials for thought, it had nothing to warrant it in saying, that this word represented any thing of which that intellect had cognizance.

This limitation of the material put at the disposal of the mind, was largely illustrated in the course of the work; and the illustrations assumed some such character as this:—Imaginative writers present us with descriptions of things which never, within our own experience, have existed,—of things which, we believe, never have had existence. Yet, however fantastic and heterogeneous may be the representations thus presented to our notice, there is no one part, of which we form a conception, that is any thing more than a new arrangement of ideas that have been left in the mind by impressions deposited there by sensation. The most extravagant of eastern or classical fictions there find their elements. If it be a three-headed dog, a winged horse, a fiery dragon, or a golden palace, that is spoken of, the reader who forms a conception of the narrative puts it together with the ideas left in his mind by impressions conveyed through the external senses. If a spectre is said to be raised, it may be spoken of as not denser than the atmosphere, yet the attributes that bring a conception of it to the intellect are the form and proportions of a human being,—expression, action, and habiliments: all elements the ideas of which the mind has received through the impressions of the senses. If words were used in a book of fiction which did not admit of being thus realized by the mind putting together a corresponding portion of the ideas stored up within it—supplying, as it were, the described costume from this wardrobe—then, according to Hume's philosophy, the word would be a sound without meaning. He maintained a like rule as to books of philosophy. If the authors used terms which were not thus represented in the storehouse of the matter of thought and language, they were not reasoning on what they knew; they were not using words as the signs of things signified, but printing unmeaning collections of letters, or uttering senseless sounds.

The system, if it were to be classed under the old metaphysical divisions, was one of nominalism. Such words as shape, colour, hardness, roughness, &c. the author of the Treatise could only admit to have a meaning in as far as they signified ideas in the mind; and these ideas could only be there as the relics of impressions derived through the senses. Thus, general terms, such as the categories of Aristotle, could have no existence except in so far as they represented and called up particulars. Of the abstract term colour, our notion is derived solely from the ideas left in the mind by the actual impressions made through the senses. Heat, cold, and largeness, so far as these words represent what is really in the mind, have no other foundation.

The application of this system to the mathematics, and to natural philosophy, was so startling as to afford to some readers almost a reductio ad absurdum. The infinite divisibility of matter was arraigned by Hume as so far from being a truth, that it was not even capable of being conceived by the mind, which had never yet received any impressions through the senses corresponding to the expression. Every man had seen matter divided—some into smaller fragments than others; but where our ideas, derived from actual experiment, stopped in minuteness of division, the conception of divisibility stopped also. The truth of geometrical demonstration, as applicable to practice, he did not deny; but he maintained, or rather seemed to maintain, for his reasoning here is of a highly subtle order, that we have a conception of these operations only in as far as they concur with really existing things, or, more properly speaking, with the ideas in the mind conveyed thither by the senses. Of the point, which has no breadth, depth, or length; of the straight line, which is deficient in the first and second, and not in the last of these qualities, he denied that we could have an idea, unless that idea were just as much the representative of an actual existence as any other idea is.

Infinity of space was an expression to which he had an objection on similar grounds; it had no idea corresponding to it lodged in the mind. Of space finite in various quantities, the mind possessed ideas stored up from repeated impressions, and by adding these ideas together, more or less vastness in the conception of finite space was afforded. But any thing beyond this definitive increase, attested as it was by the senses, the mind had no means of conceiving. Whatever might be in another intellectual world, there was no idea corresponding to infinity of space in the mind of man. It thence followed, that space unoccupied was a conception of which the mind was incapable, because the impressions originally conveyed to the mind were the medium through which the conception of space existed, and where there were no ideas of such impressions, an aggregate idea of space was wanting. In the same manner it was held, that it was in a succession of impressions, with ideas corresponding, that the conception of time consisted, and that without such a succession, time would be a thing unknown and unconceived. Our ideas of numbers he found to be but the collected ideas of the impressions of the units of which the senses have received distinct impressions; and in confirmation of this he appealed to the distinctness of our notion of small numbers, which our mind has been accustomed to find represented by units, and our imperfect conception of those large numbers, which we have never had presented to us in detail. How readily we have a notion of six, but how imperfectly the mind receives the conception of six millions; how clearly we perceive, in units, the difference between six and twelve, but how imperfect is our notion of the difference between six millions and twelve millions.[75:1]

All human consciousness being of these two materials, impressions and ideas, the answer to the question, What knowledge have we of an external world, resolved itself into this, that there were certain impressions and ideas which we supposed to relate to it—further we knew not. When we turn, according to this theory, from the external world, and, looking into ourselves, ask what certainty we have of separate self-existence, we find but a string of impressions and ideas, and we have no means of linking these together into any notion of a continuous existence. Such is that boasted thing the human intellect, when its elements are searched out by a rigid application of the sceptical philosophy of Hume. Not a thing separate and self-existent, which was, and is, and shall continue; but a succession of mere separate entities, called in one view impressions, in another ideas.[76:1]

It may make this brief sketch more clear, to notice a circumstance in the history of philosophy, which, perhaps, serves better in an incidental manner to mark the boundaries of the field of Hume's inquiry, than many pages of discursive description. The transcendentalists took him up as having examined the materials solely, on which pure reason operates; not pure reason itself. They said that he had examined the classes of matter which come before the judge, but had omitted to describe the judge himself, the extent of his jurisdiction, and his method of enforcing it. They maintained, that all these things, which with Hume appeared to be the constituent elements of philosophy, were nothing but the materials on which philosophy works,—that to presume them to be of service presupposed a reason which could make use of them,—that Hume himself, while thus speculating and telling us that his mind consisted but of a string of ideas, left behind by certain impressions, was himself making use of that pure reason which was in him before the ideas or impressions existed, and was through that power adapting the impressions and ideas to use. He characterized his system as "an attempt to introduce the experimental method of reasoning into moral subjects:" but they said that there was another and a preliminary matter of inquiry—the faculty, to speak popularly, which suggested what experiments should be made, and judged of their results.

Hume may be found indirectly lamenting the fate of his own work on metaphysics, in his remarks on other works of a kindred character; and in these criticisms we have a clue to the expectations he had formed. In his well-known rapid criticism on the literature of the epoch of the civil wars, he says of Hobbes: "No author in that age was more celebrated both abroad and at home than Hobbes. In our times, he is much neglected: a lively instance how precarious all reputations founded on reasoning and philosophy! A pleasant comedy which paints the manners of the age, and exposes a faithful picture of nature, is a durable work, and is transmitted to the latest posterity. But a system, whether physical or metaphysical, owes commonly its success to its novelty; and is no sooner canvassed with impartiality, than its weakness is discovered."

Like the majority of literary prophecies dictated by feeling and not by impartial criticism, this one, whether as it refers to "The Leviathan," of which it is ostensibly uttered, or to the "Treatise of Human Nature," the fate of which doubtless suggested it, has proved untrue. The influence of Hobbes has revived, as that of the Treatise remained undiminished from the time when it was first fully appreciated. And in both cases their influence has arisen from that element which seems alone to be capable of giving permanent value to metaphysical thought. It is not that in either case the fundamental theory of the author is adopted, as the disciples of old imbibed the system of their masters, but that each has started some novelties in thought, and, either by themselves sweeping away prevailing fallacies, or suggesting to others the means of doing so, have cleared the path of philosophy. As a general system, the philosophy of Hobbes has been perhaps most completely rejected at those times when its incidental discoveries and suggestions made it most serviceable to philosophy, and were the cause of its being most highly esteemed. "Harm I can do none," says Hobbes, when speaking of the metaphysicians who preceded him, "though I err not less than they, for I leave men but as they are, in doubt and dispute." There is indeed nothing in the later history of metaphysical writing to show that the triumphs in that department of thought are to stretch beyond the establishment of incidental truths, the removal of fallacies, and the suggestion of theories that may teach men to think. The field is a republic: incidental merit has its praise, and is allowed its pre-eminence; but no one mind, it may safely be pronounced, holds in it that monarchical sway which Adam Smith retains over the empire of political economy. The ancient systems anterior to Christianity allowed of such empire. The pupil did not follow his master merely in this and that incidental truth developed, but adopted the system in all its details and proportions as his system and his creed. In later times it would probably be found that the most devoted admirers of great writers on metaphysics do not adopt their opinions in the mass; and it seems that men must now go elsewhere than to the produce of human reason, for the grand leading principles of the philosophy of belief and disbelief.

To those who hold that the writings of the great metaphysicians are thus to be esteemed on account, not of their fundamental principles, but of the truths they bring out in detail, a new theory is like a new road through an unfrequented country, valuable, not for itself, but for the scenery which it opens up to the traveller's eye. The thinker who adopts this view, often wonders at the small beginnings of philosophical systems—wonders, perhaps, at the circumstance of Kant having believed that his own system started into life at one moment as he was reading Hume's views of Cause and Effect. But the solution is ready at hand. We feel that the philosopher of Königsberg had in his mind the impulses that would have driven him into a new path had no Hume preceded him. We owe it to the Essay on Cause and Effect that it was the starting-point at which he left the beaten track; but, had it not attracted his attention, his path would have been as original, though not, perhaps, in the same direction. And so of Hume himself. If the main outline of his theory had never occurred to him, he would still have been a great philosopher; for in some form or other he would have found his way to those incidental and subsidiary discoveries, which are admitted to have reality in them by many who repudiate his general theory.

Of all the secondary applications of the leading principle of the Treatise, none has perhaps exercised so extensive an influence on philosophy, as this same doctrine of cause and effect. Looking to those separate phenomena, of which in common language we call the one the cause of the other, and the other the effect of that cause, he could see no other connexion between them than that the latter immediately followed the former. He found that the mind, proceeding on the inductive system, when it repeatedly saw two phenomena thus conjoined, expected, when that which had been in use to precede the other made its appearance, that the other would follow; and he found that by repeated experiment this expectation might be so far strengthened, that people were ready to stake their most important temporal interests on the occurrence of the phenomenon called the effect, when that called the cause had taken place. But if there were any thing else but this conjunction, of which a knowledge was demanded—if the unsatisfied investigator sought for some power in the one phenomenon which enabled it to be the fabricator of the other—the sceptical reasoner would answer, that for all he could say to the contrary such a thing might be, but he had no clue to that knowledge—no impression of any such quality passed into his intellect through sensation—his mind had no material committed to it by which the existence or non-existence of any such thing could be argued.

The vulgar notion of this theory was, that it destroyed all our notions of regularity and system in the order of nature; that it made no provision for unseen causes, and contemplated only the application of the doctrines of cause and effect to things which were palpably seen following each other. But the inventor of the theory never questioned the regularity of the operations of nature as established by the inductive philosophy; he only endeavoured to show how far and within what limits we could acquire a cognizance of the machinery of that regularity. He denied not that when the spark was applied, the gunpowder would ignite, or that when the ball was dropped, it would proceed to the earth with the accelerated motion of gravitation; but he denied that we could see any other connexion between the cause and effect in either case, than that of uniform sequence. When it was scientifically adopted, the theory was found to be productive of the most important results. The view that when any effect was observed, that phenomenon which was most uniform in its precedence was the one entitled to be termed the cause, was a salutary incentive to close and patient investigation, by laying before the philosopher the simple, numerical question—what was that phenomenon which, by the uniformity of its precedence, was entitled to be termed the cause?[81:1] The test became of the simplest kind; and, if the experimentalist had at a particular time considered some phenomenon as a cause,—if the farther progress of patient and unprejudiced inquiry showed that another, by the occurrence of instances in which it preceded the effect while the former did not, had a preferable title to be termed the cause, the mind in its unbiassed estimate of numbers at once admitted the claim. But when, according to the antagonist system,[82:1] it became settled that any given phenomenon had in it the power of bringing into existence another, that power was viewed as a quality of the object. When things are admitted to have qualities, it is not easy for the mind at once to assent to their non-existence and to admit that others have the proper title to these qualities. Analogy, the great source of fallacies, comes to increase the difficulty, by a confusion of what are termed the qualities of bodies, and those endowments with which we invest our fellow-creatures. In this respect Hume's theory of cause and effect has been of great service to inductive philosophy.

It was an objection to it that it made no allowance for unseen causes; but it was part of its author's system, that the uniformity which our observation teaches us, proceeds unseen in those cases to which our observation cannot penetrate. It was part of the theory, that where there is a want of the absolute uniformity in the sequence of two phenomena, they are not respectively cause and effect. This principle is of vital importance in physical science. It is a notion with the vulgar, and one that sometimes perhaps lurks unseen in scientific operations, that the cause sometimes does not produce its effect by reason of some failure in the operating power. It is from a vague amplification of this heresy, that the popular notion of chance is derived. Hume's theory nips the bud of such a fallacy by denying, whenever there is a break in the sequence, that the phenomena which have in other instances followed each other, really are cause and effect. It is perhaps in the unscientific application of therapeutics, that the popular fallacy is most widely and most dangerously exemplified. The whole of the complexity of that wondrous science consists in the immediate causes and effects being unseen—in the phenomena immediately conjoined not being ascertained, but in attempts being made to estimate them through the connexion between those external causes to which the internal causes may have had the relation of effects, and those external effects of which these internal effects may have been the causes. The character of unseen causes was aptly illustrated by Hume himself, from the throwing of a die. The vulgar mind can see no cause and effect in the operation, because there is a series of causes and effects, which are hidden from the sight, in the interior of the box; but the philosopher knows not the less, that those laws of motion, which induction has established to him as truths, are taking place; and that there is no turn made by the die, which is not as much the effect of some cause, as the turning of the hands of a watch, or the parallel motion in a steam engine.

It is one of the peculiar features of the history of mental philosophy, that there is scarcely ever a new principle, associated with the name of a great author, but it is shown that it has been anticipated, in some oracular sentence, probably by an obscure writer. Joseph Glanvill is pretty well known as the author of "Saducismus Triumphatus," a vindication of the belief in witches and apparitions, which must have been perused by all the curious in this species of lore. Glanvill was the author of various tracts on biblical subjects, but it was not generally known that he wrote a book on sceptical philosophy, called "Scepsis Scientifica, or, Confest Ignorance the Way to Science," until it was unearthed by the persevering inquiries of Mr. Hallam. In that book there is the passage, "all knowledge of causes is deductive, for we know none by simple intuition, but through the medium of their effects; so that we cannot conclude any thing to be the cause of another but from its continual accompanying it, for the causality itself is insensible."[84:1] This is an addition to the many instances where writers have almost, as it were by chance, laid down principles, of which they show, by neglecting to follow them to their legitimate conclusions, that they have not understood their full meaning; if it do not rather illustrate the view already noticed, that in metaphysics our assent is secured, not to general propositions as such, but to their particular applications; and that it is not in the laying down of first principles that important truths are exhibited to the world, but in those subsidiary expositions by which the discoverer endeavours to show their application.

The subsequent history of Hume's theory of Cause and Effect, is a marked illustration of the danger of bringing forward as an argument against theories purely metaphysical, the statement that they are dangerous to religion. It is difficult to see where there is a difference between adducing that argument in the sphere of natural philosophy, from which it has been long scouted by common consent, and bringing it forward as an answer to the theories of the metaphysician. In either case it is a threat, which, in the days of Galileo, bore the terror of corporal punishment, and in the present day carries the threat of unpopularity, to the person against whom it is used.[86:1] If any one should suppose that he finds lurking in the speculations of some metaphysical writer, opinions from which it may be inferred that he is not possessed of the hopes and consolations of the Christian, humanity to the unhappy author should suggest that he ought rather to be pitied than condemned, and respect for the religious feelings of others should teach that there is no occasion to endeavour, by a laborious pleading, to demonstrate that a man who has said nothing against religion is in reality an enemy to Christianity. They are surely no enlightened friends to religion, who maintain that the suppression of inquiry as to the material or the immaterial world, is favourable to the cause of revealed truth. The blasphemer who raises his voice offensively and contentiously against what his fellow citizens hold sacred, invokes the public wrath, and is no just object of sympathy. The extent of his punishment is regretted only when, by its vindictive excess, it is liable to excite retaliatory attacks from the same quarter. But the speculative philosopher, who does not directly interfere with the religion of his neighbours, should be left to the peaceful pursuit of his inquiries; and those who, instead of meeting him by fair argument, cry out irreligion, and call in the mob to their aid, should reflect first, whether it is absolutely certain that they are right in their conclusion, that his inquiries, if carried out, would be inimical to religion—whether some mind more acute and philosophical than their own, may not either finally confute the sceptical philosopher's argument, or prove that it is not inimical to religion; and secondly, whether they are not likely to be themselves the greatest foes to religion, by holding that it requires such defence, and the practical blasphemers, by proclaiming that religion is in danger?

Kant, the most illustrious opponent of Hume, in allusion to those who have appealed against him to our religious feelings, asks, what the man is doing that we should meddle with him; says he is but trying the strength of human reason, and bids us leave him to combat with those who are giving him specimens of the fabric on which to try his skill—tells us to wait and see who will produce one too strong to be broken to pieces—and not cry treason, and appeal to the angry multitude, who are strangers to these refined reasonings, to rush in. Shall we ask reason to give us lights, and prescribe beforehand what they are to show us?[88:1] "The observation of human blindness and weakness," says Hume himself, "is the result of all philosophy, and meets us at every turn, in spite of our endeavours to elude or avoid it." A solemn saying, and characteristic of one who has done more than any other man to show the feebleness of poor human reason, and to teach man that he is not all sufficient to himself.

Those revelations in astronomy and geology, the first glimmerings of which made the timid if not doubting friends of their cause tremble, have enlarged year by year in rapid progression; but revealed religion is not less firm on her throne; and many of those who held that Hume's theory of Cause and Effect was inimical to revelation, lived to see how startlingly that argument could be turned against themselves. It has been well observed by Dugald Stewart, that this theory is the most effectual confutation of the gloomy materialism of Spinoza, "as it lays the axe to the very root from which Spinozism springs." "The cardinal principle," he says, "on which the whole of that system turns is, that all events, physical and moral, are necessarily linked together as causes and effects; from which principle all the most alarming conclusions adopted by Spinoza follow as unavoidable and manifest corollaries. But if it be true, as Mr. Hume contends, and as most philosophers now admit, that physical causes and effects are known to us merely as antecedents and consequents; still more if it be true that the word necessity, as employed in this discussion, is altogether unmeaning and insignificant, the whole system of Spinoza is nothing better than a rope of sand, and the very proposition which it professes to demonstrate is incomprehensible by our faculties."[89:1]

It will be remembered how signally, in the question in the General Assembly of the Church of Scotland, as to Sir John Leslie's professorship, the argument of irreligion was retaliated; and it was shown that, in the theory of an existing machinery in nature enabling the universe to proceed in its regular course, the cause having within it the adequate power for producing its effect, the omnipresence of a Deity was dispensed with, and there was substituted for the all-pervading influence of a superior wisdom, a mere material machine, having within itself the elements of its own regular motion. Thus, in instances where writers have claimed credit for having aided the cause of religion by carrying out the principles of natural theology, this merit has in many cases, and among certain classes of devout religious thinkers, been sternly denied them; and it has been said that their labours are rather adverse than favourable to revealed religion, because, through their tendency to make people believe in an established order in nature, by which causes produce their effects according to a fixed system, they have the effect of making mankind forget the existence of a revealed, omnipresent Deity, whose all-competent superintendence regulates the world, and they supply a religion independent of the religion of revelation.

Perhaps in this little history we may find an illustration of the view, that the greatest service which the Treatise has done to philosophy is that purely incidental one of teaching human reason its own weakness—of showing how easily the noblest fabric of human thought may be undermined, by a destroying agency of power not greater than that of the constructive genius which has raised it. In this respect it has done to philosophy the invaluable service of teaching philosophers their own fallibility. In all the departments of thought, and not only in the world of thought but in that of action, the spirit of human infallibility is the greatest obstacle to truth and goodness. Whether it appear to protect a system which the thinker has framed for himself, or assume the more modest shape of maintaining, that among conflicting systems he has made choice of that which is absolutely and certainly right, while all others which in any way differ from it are as absolutely and certainly wrong; this offspring of the pride of human intellect is an equally dangerous enemy of human improvement; and to have contributed to its downfal is of itself no small achievement for one mind.

Such are a few remarks on the matter of the first part of the "Treatise of Human Nature"—given not by any means as an analysis of the doctrines there taught, but merely as an attempt to characterize them by their prominent features. It will naturally be expected that a similar attempt should be made to characterize the form in which these doctrines were promulgated. As to the style of the Treatise, it possesses the clearness, flexibility, and simplicity that distinguish the maturity of its author's literary career, though not quite in all the perfection in which they afterwards attended his pen. There are occasional Scoticisms—a defect which he took infinite pains to cure, but of which he was never entirely rid. He uses a few obsolete and now harsh sounding forms of expression, from which he afterwards abstained: such as the elliptical combination 'tis, for it is. Here, and in the first editions of his History, he frequently neglects the increment on the perfect tense, as by saying, "I have forgot," instead of, I have forgotten; "I have wrote," instead of I have written.

The Treatise has that happy equality of flight, which distinguishes the author's maturer productions. There is no attempt to soar, and none of those ambitious inequalities which often deform the works of young authors. His imagination and language seem indeed to have been kept permanently chained down by the character of his inquiries. His constant aim is to make his meaning clear; and in the subtleties of a new and intricate system of metaphysics, he seems to have felt that there lay upon him so heavy a responsibility to make use on all occasions of the clearest and simplest words, that any flight of imagination or eloquence would be a dangerous experiment.

There is a corresponding absence of pedantic ornament. A young writer who has read much, is generally more anxious to show his learning and information than his own power of thought. With many the defect lasts through maturer years, and they write as if to find a good thing in some unknown author, were more meritorious than to have invented it. Montesquieu, whom Hume has been accused of imitating, carried this defect to a vice, and often distorted the order of his reasoning, that he might introduce an allusion to something discovered in the course of his peculiar learning. That Hume had read much in philosophy before he undertook his great work, cannot be doubted, but he does not drag his readers through the minutiæ of his studies, and is content with giving them results. In many respects, indeed, one would have desired to know more of his appreciation of his predecessors. The name of Aristotle is, it is believed, not once mentioned in the work, and there are only some indirect allusions to him, and these not very respectful, in casual remarks on the opinions of the Peripatetics. One would have expected from Hume a kindred sympathy with the great master of intellectual philosophy, and a respectful appreciation of one whose inquiries were conducted with a like acute severity, but whose mind took so much more wide and comprehensive a grasp of the sources of human knowledge.

It has been often observed, that a person so original in his opinions as Hume, ought to have made a new nomenclature for the new things which he taught. But he has no philosophical nomenclature; he appears indeed to have despised that useful instrument of method, and means of communicating clear ideas to learners. This want has prevented his system from being clearly and fully learned by the student, while it has at the same time probably made his works less repulsive to the general reader. He seems indeed hardly to have been conscious of the advantage to all philosophy, of uniformity of expression. Using the words "force," "vivacity," "solidity," "firmness," and "steadiness," all with the same meaning, he speaks of this usage as a "variety of terms which may seem so unphilosophical;" and then observes, more in the style of one who is tired of philosophical precision than of a philosopher, "Provided we agree about the thing, 'tis needless to dispute about the terms."

This is a kindred defect to that absence of method which has been already taken notice of. A fixed nomenclature is a beacon against repetition and discursiveness. But the Treatise has no pretension to be a work of which he who omits paying attention to any part, thereby drops a link in a chain, the loss of which will make the whole appear broken and inconsistent. There are, it is true, places where the essential parts of the author's philosophy are developed, the omission of which would render that which follows hard to be understood, but in general each department of the work is intelligible in itself. Its author appears to have composed it in separate fragments; holding in view, while he was writing each part, the general principle of his theory, but not taking it for granted that the reader is so far master of that principle, as not to require it to be generally explained in connexion with the particular matter under consideration. He seems indeed rather desirous to dwell on it, as something that the reader may have seen in the earlier part of the work, but may have neglected to keep in his mind while he reads the other parts. Perhaps the true model of every philosophical work is to be found in the usual systems of geometry, where, whatever is once proposed and proved, is held a fixed part of knowledge, and is never repeated; but as far as psychological reasoning is from the certainty of geometrical, so distant perhaps, will ever be the precision of its method from that of geometry.

It may safely be pronounced, that no book of its age presents itself to us at this day, more completely free from exploded opinions in the physical sciences. With the exception perhaps of occasional allusions to "animal spirits," as a moving influence in the human body, the author's careful sifting sceptical mind seems, without having practically tested them, to have turned away from whatever doctrines were afterwards destined to fall before the test of experiment and induction. It was not that he was so much of a natural philosopher himself as to be able to test their truth or falsehood, but that with a wholesome jealousy, characteristic of the mind in which the Disquisition on Miracles was working itself into shape, he avoided them as things neither coming within the scope of his own analysis, nor bearing the marks of having been satisfactorily established by those whose more peculiar province it was to investigate their claims to be believed. At a later date, his friend D'Alembert admitted judicial astrology and alchemy as branches of natural philosophy in his "Systême Figuré des Connoissances Humaines." Cudworth, and even the scrutinizing Locke, dealt gravely with matters doomed afterwards to be ranked among popular superstitions, and Sir Thomas Browne, in some respects a sceptic, eloquently defended more "vulgar errors" than he exposed. Hobbes was, in the midst of the darkest scepticism, a practical believer in the actual presence of the spirits of the air; and Johnson, whose name, however, it may scarcely be fair to class in this list, as he did not profess, except for conversational triumph, to be a reducer and demolisher of unfounded beliefs, along with his partial admission of the existence of spectres, has left behind him many dogmatic announcements of physical doctrines, which the progress of science has now long buried under its newer systems.

It is by no means maintained that Hume was beyond his age—or even on a par with its scientific ornaments, in physical knowledge; but merely that he showed a judicious caution in distinguishing, in his published work, those parts of physical philosophy which had been admitted within the bounds of true and permanent science, from those which were still in a state of mere hypothesis. His knowledge of physical science was probably not very extensive. A small portion of a collection of his notes on subjects that attracted his attention bear on this subject. The collection from which they are taken will be noticed in the next chapter; but as those which are set apart from the others, and are headed "Natural Philosophy," seem to have been written at an earlier period than the rest of the collection, and are appropriate to the present subject, they are here given. It is not expected that they will awaken in the natural philosopher any great respect for the extent of Hume's inquiries in this department of knowledge.