Hume, therefore, believed that all the secrets of the external world are wrapped up in the human mind. The mind was not only the key by which the treasure could be unlocked; it was also the treasure itself. Learning and science might illustrate and beautify our mental acquisitions, but they could not communicate real knowledge; they could neither give the prime original materials, nor could they teach the design according to which those materials must be worked.
In conformity with these views, the Natural History of Religion was composed. The object of Hume in writing it, was, to ascertain the origin and progress of religious ideas; and he arrives at the conclusion, that the worship of many Gods must, every where, have preceded the worship of one God. This, he regards as a law of the human mind, a thing not only that always has happened, but that always must happen. His proof is entirely speculative. He argues that the earliest state of man is necessarily a savage state; that savages can feel no interest in the ordinary operations of nature, and no desire to study the principles which govern those operations; that such men must be devoid of curiosity on all subjects which do not personally trouble them; and that, therefore, while they neglect the usual events of nature, they will turn their minds to the unusual ones.716 A violent tempest, a monstrous birth, excessive cold, excessive rain, sudden and fatal diseases, are the sort of things to which the attention of the savage is confined, and of which alone he desires to know the causes. Directly he finds that such causes are beyond his control, he reckons them superior to himself, and, being incapable of abstracting them, he personifies them; he turns them into deities; polytheism is established; and the earliest creed of mankind assumes a form which can never be altered, as long as men remain in this condition of pristine ignorance.717
These propositions, which are not only plausible, but which are probably true, ought, according to the inductive philosophy, to have been generalized from a survey of facts; that is, from a collection of evidence respecting the state of religion and of the speculative faculties among savage tribes. But this, Hume abstains from doing. He refers to none of the numerous travellers who have visited such people; he does not, in the whole course of his work, mention even a single book where facts respecting savage life are preserved. It was enough for him, that the progress from a belief in many Gods to a belief in one God, was the natural progress; which is saying, in other words, that it appeared to his mind to be the natural progress.718 With that, he was satisfied. In other parts of his essay, where he treats of the religious opinions of the ancient Greeks and Romans, he displays a tolerable, though by no means remarkable, learning; but the passages which he cites, do not refer to that entirely barbarous society in which, as he supposes, polytheism first arose. The premisses, therefore, of the argument are evolved out of his own mind. He reasons deductively from the ideas which his powerful intellect supplied, instead of reasoning inductively from the facts which were peculiar to the subject he was investigating.
Even in the rest of his work, which is full of refined and curious speculation, he uses facts, not to demonstrate his conclusions, but to illustrate them. He, therefore, selected those facts which suited his purpose, leaving the others untouched. And this, which many critics would call unfair, was not unfair in him; because he believed, that he had already established his principles without the aid of those facts. The facts might benefit the reader, by making the argument clearer, but they could not strengthen the argument. They were more intended to persuade than to prove; they were rather rhetorical than logical. Hence, a critic would waste his time if he were to sift them with a minuteness which would be necessary, supposing that Hume had built an inductive argument upon them. Otherwise, without going far, it might be curious to contrast them with the entirely different facts which Cudworth, eighty years before, had collected from the same source, and on the same subject. Cudworth, who was much superior to Hume in learning, and much inferior to him in genius,719 displayed, in his great work on the Intellectual System of the Universe, a prodigious erudition, to prove that, in the ancient world, the belief in one God was a prevailing doctrine. Hume, who never refers to Cudworth, arrives at a precisely opposite conclusion. Both quoted ancient writers; but while Cudworth drew his inferences from what he found in those writers, Hume drew his from what he found in his own mind. Cudworth, being more learned, relied on his reading; Hume, having more genius, relied on his intellect. Cudworth, trained in the school of Bacon, first collected the evidence, and then passed the judgment. Hume, formed in a school entirely different, believed that the acuteness of the judge was more important than the quantity of the evidence; that witnesses were likely to prevaricate; and that he possessed, in his own mind, the surest materials for arriving at an accurate conclusion. It is not, therefore, strange, that Cudworth and Hume, pursuing opposite methods, should have obtained opposite results, since such a discrepancy is, as I have already pointed out, unavoidable, when men investigate, according to different plans, a subject which, in the existing state of knowledge, is not amenable to scientific treatment.
The length to which this chapter has already extended, and the number of topics which I have still to handle, will prevent me from examining, in detail, the philosophy of Reid, who was the most eminent among the purely speculative thinkers of Scotland, after Hume and Adam Smith, though, in point of merit, he must be placed far below them. For, he had neither the comprehensiveness of Smith, nor the fearlessness of Hume. The range of his knowledge was not wide enough to allow him to be comprehensive; while a timidity, almost amounting to moral cowardice, made him recoil from the views advocated by Hume, not so much on account of their being false, as on account of their being dangerous. It is, however, certain, that no man can take high rank as a philosopher, who allows himself to be trammelled by considerations of that kind. A philosopher should aim solely at truth, and should refuse to estimate the practical tendency of his speculations. If they are true, let them stand; if they are false, let them fall. But, whether they are agreeable or disagreeable, whether they are consolatory or disheartening, whether they are safe or mischievous, is a question, not for philosophers, but for practical men. Every new truth which has ever been propounded, has, for a time, caused mischief; it has produced discomfort, and often unhappiness, sometimes by disturbing social or religious arrangements, and sometimes merely by the disruption of old and cherished associations of thought. It is only after a certain interval, and when the framework of affairs has adjusted itself to the new truth, that its good effects preponderate; and the preponderance continues to increase, until, at length, the truth causes nothing but good. But, at the outset, there is always harm. And, if the truth is very great, as well as very new, the harm is serious. Men are made uneasy; they flinch; they cannot bear the sudden light; a general restlessness supervenes; the face of society is disturbed, or perhaps convulsed; old interests, and old beliefs, are destroyed, before new ones have been created. These symptoms are the precursors of revolution; they have preceded all the great changes through which the world has passed; and while, if they are not excessive, they forebode progress, so if they are excessive, they threaten anarchy. It is the business of practical men to moderate such symptoms, and to take care that the truths which philosophers discover, are not applied so rashly as to dislocate the fabric, instead of strengthening it. But the philosopher has only to discover the truth, and promulgate it; and that is hard work enough for any man, let his ability be as great as it may. This division of labour, between thinkers and actors, secures an economy of force, and prevents either class from wasting its power. It establishes a difference between science, which ascertains principles, and art, which applies them. It also recognizes, that the philosopher and the practical man, having each a separate part to play, each is, in his own field, supreme. But it is a sad confusion for either to interfere with the other. In their different spheres, both are independent, and both are worthy of admiration. Inasmuch, however, as practical men should never allow the speculative conclusions of philosophers, whatever be their truth, to be put in actual operation, unless society is, in some degree, ripe for their reception; so, on the other hand, philosophers are not to hesitate, and tremble, and stop short in their career, because their intellect is leading them to conclusions subversive of existing interests. The duty of a philosopher is clear. His path lies straight before him. He must take every pains to ascertain the truth; and, having arrived at a conclusion, he, instead of shrinking from it because it is unpalatable, or because it seems dangerous, should on that very account, cling the closer to it, should uphold it in bad repute, more zealously than he would have done in good repute; should noise it abroad far and wide, utterly regardless what opinions he shocks, or what interests he imperils; should, on its behalf, court hostility and despise contempt, being well assured, that, if it is not true, it will die, but that, if it is true, it must produce ultimate benefit, albeit unsuited for practical adoption by the age or country in which it is first propounded.
But Reid, notwithstanding the clearness of his mind and his great powers of argument, had so little of the real philosophic spirit, that he loved truth, not for its own sake, but for the sake of its immediate and practical results. He himself tells us, that he began to study philosophy, merely because he was shocked at the consequences at which philosophers had arrived. As long as the speculations of Locke and of Berkeley were not pushed to their logical conclusions, Reid acquiesced in them, and they were good in his eyes.720 While they were safe and tolerably orthodox, he was not over-nice in inquiring into their validity. In the hands of Hume, however, philosophy became bolder and more inquisitive; she disturbed opinions which were ancient, and which it was pleasant to hold; she searched into the foundation of things, and by forcing men to doubt and to inquire, she rendered inestimable service to the cause of truth. But this was precisely the tendency at which Reid was displeased. He saw that such disturbance was uncomfortable; he saw that it was hazardous; therefore, he endeavoured to prove that it was groundless. Confusing the question of practical consequences with the totally different question of scientific truth, he took for granted that, because to his age the adoption of those consequences would be mischievous, they must be false. To the profound views of Hume respecting causation, he gravely objects, that if they were carried into effect, the operation of criminal law would be imperilled.721 To the speculations of the same philosopher concerning the metaphysical basis of the theory of contracts, he replies, that such speculations perplex men, and weaken their sense of duty; they are, therefore, to be disapproved of, on account of their tendency.722 With Reid, the main question always is, not whether an inference is true, but what will happen if it is true. He says, that a doctrine is to be judged by its fruits;723 forgetting that the same doctrine will bear different fruits in different ages, and that the consequences which a theory produces in one state of society, are often diametrically opposed to those which it produces in another. He thus made his own age the standard of all future ones. He also trammelled philosophy with practical considerations; diverting thinkers from the pursuit of truth, which is their proper department, into the pursuit of expediency, which is not their department at all. Reid was constantly stopping to inquire, not whether theories were accurate, but whether it was advisable to adopt them; whether they were favourable to patriotism, or to generosity, or to friendship;724 in a word, whether they were comfortable, and such as we should at present like to believe.725 Or else, he would take other ground, still lower, and still more unworthy of a philosopher. In opposing, for instance, the doctrine, that our faculties sometimes deceive us, – a doctrine which, as he well knew, had been held by men whose honesty was equal to his own, and whose ability was superior to his own, – he does not scruple to enlist on his side the prejudices of a vulgar superstition; seeking to blacken the tenet which he was unable to refute. He actually asserts, that they who advocate it, insult the Deity, by imputing to the Almighty that He has lied. Such being the consequence of the opinion, it of course follows that the opinion must be rejected without further scrutiny, since, to accept it, would produce fatal results on our conduct, and would, indeed, be subversive of all religion, of all morals, and of all knowledge.726
In 1764, Reid published his Inquiry into the Human Mind; and in that, and in his subsequent work, entitled Essays on the Powers of the Mind, he sought to destroy the philosophy of Locke, Berkeley, and Hume. And as Hume was the boldest of the three, it was chiefly his philosophy which Reid attacked. Of the character of this attack, some specimens have just been given; but they rather concern his object and motives, while what we have now to ascertain is, his method, that is, the tactics of his warfare. He clearly saw, that Hume had assumed certain principles, and had reasoned deductively from them to the facts, instead of reasoning inductively from the facts to them. To this method, he strongly, and perhaps fairly, objects. He admits that Hume had reasoned so accurately, that if his principles were conceded, his conclusions must likewise be conceded.727 But, he says, Hume had no right to proceed in such a manner. He had no right to assume principles, and then to argue from them. The laws of nature were to be arrived at, not by conjecturing in this way, but by a patient induction of facts.728 Discoveries depended solely on observation and experiment; and any other plan could only produce theories, ingenious, perhaps, and plausible, but quite worthless.729 For, theory should yield to fact, and not fact to theory.730 Speculators, indeed, might talk about first principles, and raise a system by reasoning from them. But, the fact was, that there was no agreement as to how a first principle was to be recognized; since a principle which one man would deem self-evident, another would think it necessary to prove, and a third would altogether deny.731
The difficulties of deductive reasoning are here admirably portrayed. It might have been expected, that Reid would have built up his own philosophy according to the inductive plan, and would have despised that assumption of first principles, with which he taunts his opponents. But it is one of the most curious things in the history of metaphysics, that Reid after impeaching the method of Hume, follows the very same method himself. When he is attacking the philosophy of Hume, he holds deduction to be wrong. When he is raising his own philosophy, he holds it to be right. He deemed certain conclusions dangerous, and he objects to their advocates, that they argued from principles, instead of from facts: and that they assumed themselves to be in possession of the first principles of truth, although people were not agreed as to what constituted a first principle. This is well put, and hard to answer. Strange, however, to say, Reid arrives at his own conclusions, by assuming first principles to an extent far greater than had been done by any writer on the opposite side. From them, he argues; his whole scheme is deductive; and his works scarcely contain a single instance of that inductive logic, which, when attacking his opponents, he found it convenient to recommend. It is difficult to conceive a better illustration of the peculiar character of the Scotch intellect in the eighteenth century, and of the firm hold, which, what may be called, the anti-Baconian method, had upon that intellect. Reid was a man of considerable ability, of immaculate honesty, and was deeply convinced that it was for the good of society that the prevailing philosophy should be overthrown. To the performance of that task, he dedicated his long and laborious life; he saw that the vulnerable point of the adverse system was its method; he indicated the deficiencies of that method, and declared, perhaps wrongly, but at all events sincerely, that it could never lead to truth. Yet, and notwithstanding all this, such was the pressure of the age in which he lived, and so completely did the force of circumstances shape his understanding, that, in his own works, he was unable to avoid that very method of investigation which he rebuked in others. Indeed, so far from avoiding it, he was a slave to it. The evidence of this I will now give, because, besides its importance for the history of the Scotch mind, it is valuable as one of many lessons, which teach us how we are moulded by the society which surrounds us; how even our most vigorous actions are influenced by general causes of which we are often ignorant, and which few of us care to study; and, finally, how lame and impotent we are, when, as individuals, we try to stem the onward current, resisting the great progress instead of aiding it, and vainly opposing our little wishes to that majestic course of events, which admits of no interruption, but sweeps on, grand and terrible, while generation after generation passes away, successively absorbed in one mighty vortex.
Directly Reid, ceasing to refute the philosophy of Hume, began to construct his own philosophy, he succumbed to the prevailing method. He now assures us, that all reasoning must be from first principles, and that, so far from reasoning to those principles, we must at once admit them, and make them the basis of all subsequent arguments.732 Having admitted them, they become a thread to guide the inquirer through the labyrinth of thought.733 His opponents had no right to assume them, but he might do so, because to him they were intuitive.734 Whoever denied them, was not fit to be reasoned with.735 Indeed, to investigate them, or to seek to analyze them, was wrong as well as foolish, because they were part of the constitution of things; and of the constitution of things no account could be given, except that such was the will of God.736
As Reid obtained his first principles with such ease, and as he carefully protected them by forbidding any attempt to resolve them into simpler elements, he was under a strong temptation to multiply them almost indefinitely, in order that, by reasoning from them, he might raise a complete and harmonious system of the human mind. To that temptation he yielded with a readiness, which is truly surprising, when we remember how he reproached his opponents with doing the same thing. Among the numerous first principles which he assumes, not only as unexplained, but as inexplicable, are the belief in Personal Identity;737 the belief in the External World;738 the belief in the Uniformity of Nature;739 the belief in the Existence of Life in Others;740 the belief in Testimony;741 also in the power of distinguishing truth from error,742 and even in the correspondence of the face and voice to the thoughts.743 Of belief generally, he asserts that there are many principles,744 and he regrets that any one should have rashly attempted to explain them.745 Such things are mysterious, and not to be pried into. We have also other faculties, which being original and indecomposable, resist all inductive treatment, and can neither be resolved into simpler elements, nor referred to more general laws. To this class, Reid assigns Memory,746 Perception,747 Desire of Self-Approbation,748 and not only Instinct, but even Habit.749 Many of our ideas, such as those concerning Space and Time, are equally original;750 and other first principles there are, which have not been enunciated, but from which we may reason.751 They, therefore, are the major premisses of the argument; no reason having yet been given for them, they must be simple; and not having yet been explained, they are, of course, inexplicable.752
All this is arbitrary enough. Still, in justice to Reid, it must be said, that, having made these assumptions, he displayed remarkable ability in arguing from them, and that, in attacking the philosophy of his time, he subjected it to a criticism, which has been extremely serviceable. His lucidity, his dialectic skill, and the racy and masculine style in which he wrote, made him a formidable opponent, and secured to his objections a respectful hearing. To me, however, it appears, that notwithstanding the attempts, first of M. Cousin, and afterwards of Sir William Hamilton, to prop up his declining reputation, his philosophy, as an independent system, is untenable, and will not live. In this I may be mistaken; but what is quite certain is, that nothing can be more absurd than to suppose, as some have done, that he adopted the inductive, or, as it is popularly called, Baconian method. Bacon, indeed, would have smiled at such a disciple, assuming all sorts of major premisses, taking general principles for granted with the greatest recklessness, and reserving his skill for the task of reasoning from propositions for which he had no evidence, except that on a cursory, or, as he termed it, a common-sense, inspection, they appeared to be true.753 This refusal to analyze preconceived notions, comes under the head of what Bacon stigmatized as the anticipatio naturæ, and which he deemed the great enemy of knowledge, on account of the dangerous confidence it places in the spontaneous and uncorrected conclusions of the human mind. When, therefore, we find Reid holding up the Baconian philosophy, as a pattern which it behoves all inquirers to follow;754 and when we, moreover, find Dugald Stewart, who, though a somewhat superficial thinker, was, at all events, a careful writer, supposing that Reid had followed it,755 we meet with fresh proof of how difficult it was for Scotchmen of the last age to imbibe the true spirit of inductive logic, since they believed, that a system which flagrantly violated its rules, had been framed in strict accordance with them.
Leaving mental philosophy, I now come to physical science, in which, if anywhere, we might expect that the inductive plan would predominate, and would triumph over the opposite, or deductive, one. How far this was the case, I will endeavour to ascertain, by an examination of the most important discoveries which have been made by Scotchmen concerning the organic and inorganic world. And, as my object is merely to indicate the turn and character of the Scotch mind, I shall avoid all details respecting the practical effects of those discoveries, and shall confine myself to such a narration as will exhibit their purely scientific aspect, so as to enable the reader to understand what additions were made to our knowledge of the laws of nature, and in what way the additions were made. The character of each discovery, and its process, will be stated, but nothing more. Neither here, nor in any part of this Introduction, do I pretend to investigate questions of practical utility, or to trace the connexion between the discoveries of science and the arts of life. That I shall do in the body of the work itself, where I hope to explain a number of minute social events, many of which are regarded as isolated, if not incongruous. For the present, I solely aim at those broad principles, which, by marking out the epochs of thought, underlie the whole fabric of society, and which must be clearly apprehended before history can cease to be a mere empirical assemblage of facts, of which the scientific basis being unsettled, the true order and coherence must be unknown.
Among the sciences which concern the inorganic world, the laws of heat occupy a conspicuous place. On the one hand, they are connected with geology, being intimately allied, and, indeed, necessarily bound up, with every speculation respecting the changes and present condition of the crust of the earth. On the other hand, they touch the great questions of life, both animal and vegetable; they have to do with the theory of species, and of race; they modify soil, food, and organization; and to them we must look for valuable help towards solving those great problems in biology, which, of late years, have occupied the attention of the boldest and most advanced philosophers.
Our present knowledge of the laws of heat, may be briefly stated as branching into five fundamental divisions. These are: latent heat; specific heat; the conduction of heat; the radiation of heat; and, finally, the undulatory theory of heat; by which last, we are gradually discarding our old material views, and are accustoming ourselves to look upon heat as simply one of the forms of force, all of which, such as light, electricity, magnetism, motion, gravitation, and chemical affinity, are constantly assuming each other's shape, but, in their total amount, are incapable either of increase or of diminution.756 This grand conception, which is now placing the indestructibility of force on the same ground as the indestructibility of matter, has an importance far above its scientific value, considerable as that undoubtedly is. For, by teaching us, that nothing perishes, but that, on the contrary, the slightest movement of the smallest body, in the remotest region, produces results which are perpetual, which diffuse themselves through all space, and which, though they may be metamorphosed, cannot be destroyed, it impresses us with such an exalted idea of the regular and compulsory march of physical affairs, as must eventually influence other and higher departments of inquiry. Our habits of thought are so connected and interwoven, that notions of law and of the necessary concatenation of things, can never be introduced into one field of speculation, without affecting other fields which lie contiguous to it. When, therefore, the modern doctrine of conservation of force,757 becomes firmly coupled with the older doctrine of conservation of matter, we may rest assured that the human mind will not stop there, but will extend to the study of Man, inferences analogous to those already admitted in the study of Nature. Having once recognized that the condition of the material universe, at any one moment, is simply the result of every thing which has happened at all preceding moments, and that the most trivial disturbance would so violate the general scheme, as to render anarchy inevitable, and that, to sever from the total mass even the minutest fragment, would, by dislocating the structure, bury the whole in one common ruin, we, thus admitting the exquisite adjustment of the different parts, and discerning, too, in the very beauty and completeness of the design, the best proof that it has never been tampered with by the Divine Architect, who called it into being, in whose Omniscience both the plan, and the issue of the plan, resided with such clearness and unerring certainty, that not a stone in that superb and symmetrical edifice has been touched since the foundation of the edifice was laid, are, by ascending to this pitch and elevation of thought, most assuredly advancing towards that far higher step, which it will remain for our posterity to take, and which will raise their view to so commanding a height, as to insure the utter rejection of those old and eminently irreligious dogmas of supernatural interference with the affairs of life, which superstition has invented, and ignorance has bequeathed, and the present acceptance of which betokens the yet early condition of our knowledge, the penury of our intellectual resources, and the inveteracy of the prejudices in which we are still immersed.
It is, therefore, natural, that the physical doctrine of indestructibility applied to force as well as to matter, should be essentially a creation of the present century, notwithstanding a few allusions made to it by some earlier thinkers, all of whom, however, groped vaguely, and without general purpose. No preceding age was bold enough to embrace so magnificent a view as a whole, nor had any preceding philosophers sufficient acquaintance with nature to enable them to defend such a conception, even had they desired to entertain it. Thus, in the case now before us, it is evident, that while heat was believed to be material, it could not be conceived as a force, and therefore no one could grasp the theory of its metamorphosis into other forces; though there are passages in Bacon which prove that he wished to identify it with motion. It was first necessary to abstract heat into a mere property or affection of matter, and there was no chance of doing this until heat was better understood in its immediate antecedents, that is, until, by the aid of mathematics, its proximate laws had been generalized. But, with the single exception of Newton, whose efforts, notwithstanding his gigantic powers, were, on this subject, very unsatisfactory, and who, moreover, had a decided leaning towards the material theory, no one attempted to unravel the mathematical laws of heat till the latter half of the eighteenth century, when Lambert and Black began the career which Prevost and Fourier followed up. The mind, having been so slow in mastering the preliminaries and outworks of the inquiry, was not ripe for the far more difficult enterprise of idealizing heat itself, and so abstracting it, as to strip it of its material attributes, and leave it to nothing but the speculative notion of an immaterial force.