Inquiry into the limits and peculiar objects of physical and metaphysical science, tending principally to illustrate the nature of causation, etc

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I N Q V I R Y INTO THE LIMITS AND PECULIAR OBJECTS OF PHYSICAL AND METAPHYSICAL SCIENCE, TENDING PRINCIPALLY TO ILLUSTRATE THE NATURE OF CAUSATION; AND THE OPINIONS OF PHILOSOPHERS, ANCIENT AND MODERN, CONCERNING THAT RELATION, BY R. E. SCOTT, A. M. PHOFESSOR OF MORAL PHILOSOPHY IN THE UNIVERSITY AND KINc's COLLEGE OF ABERDEEN. EDINBURGH: Printed by A. and J. Aikman, •tor oliphant and ealfour, brown and crombie, and adam black, Edinburgh: and LONGMAN, HURST, KEES, AND ORME, JOHN "MURRAY; and F. C. AND J, RIVINGTONS, LONDON. 1810. TO DUGALD STEWART, PROFESSOR OF MORAL PHILOSOPHY IN THE UNIVERSITY OF EDINBURGH. Dear Sir, It is with no common degree of satisfaction that I usher this work into the world, under the auspices of a name to which the science which it professes to illustrate, owes so many valuable improvements.

In the philoso phy of the human mind, I shall always be proud to acknowledge myself your disciple ; and I shall ever reflect with delight upon the mingled instruction and pleasure which I have derived both from your writings and your lectures. If, in a former work, I have taken the liber ty to dissent from certain conclusions to which your ingenious reasonings lead ; I have had the satisfaction to experience, on your part, the most candid reception of my objections. And if, on the present occasion, I shall be found to support some opinions which you have contro verted, I have no apprehension, on that account, of any diminution of your good will. That genuine spirit of philosophy which you possess, approves the diversity of opinion which arises only from a love of truth ; and encourages that freedom of inquiry which is not inconsistent with candour and liberality.

It is the object of the following work, to in vestigate a subject which has, at all times, occasioned some controversy in the philosophical world; and which of late has, in this country, attracted a more than ordinary share of public attention. I will not deny, that the keenness with which the question concerning the relation of Cause and Effect was recently agitated, has had a considerable share in fixing my thoughts upon that subject; but this has not been the sole occasion of the following inquiry. The question came under my review, in the arrangement of V hrst principles of knowledge which I have pro posed in a former work ; and I have there offered some of the opinions which are introduced into the present investigation. I was, however, unable, upon that occasion, fully to discuss the nature of this relation; and I hope I shall not be thought to err, in deeming the question of sufficient consequence to form the subject of a separate work ; when the very important con clusions which depend upon it as an elementary principle, in the philosophy both of body and mind, are duly considered.

Introduction

. 1 HERE are few principles by which the human mind is actuated, that have more powerful effects than curiosity. This is the great stimulus of the intellectual exertions of man, and the principal in citement to those laborious investigations which the cultivation both of science and of art requires. The operation of this powerful principle may be distinct ly traced in every age and in every condition ; it is discernible in the untutored savage as well as in the civilized and cultivated member of polite society. The infant, even before it can speak, is found to be busily employed in examining whatever lies within the reach of its limited power. No sooner does it attain the use of language, than it asks a thousand questions concerning every thing it sees. It seems anxious to learn, as far as may be, the pre cise nature of every object ; and trinkets and play. things frequently fall a sacrifice to this eager desire, to scrutinize the structure of whatever comes in its way. Nature seems to have kindly provided, that at this period of life, when there is so much to be A ■2

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. learnt, the important principle of curiosity should be peculiarly active. When man has arrived at maturity, he is prompted by curiosity to undergo the greatest labours, and to encounter the most serious dangers. Stimulated by this all-powerful principle, he will forsake his peaceful home, and voluntarily renounce the comforts of civilized life, the endearments of friendship and society, to explore unknown and distant regions of the earth. He will resign himself to the tempestuous ocean, or brave the dangers of the burning desert or unhospitable wilderness, in risk of perishing by famine or fatigue ; and deem himself amplyrewarded, if at length he shall be able to visit those unexplored countries, on which his fancy had so long been fixed ;. and where, when he once arrives, he soon forgets his toils and dangers in the delights which his gratified curiosity imparts.* It is to the principle of curiosity, that science in a great measure, owes its birth and its constant pro gression towards perfection.

Man looks upon the objects and events of nature with a higher interest than that which arises from a mere regard to his own benefit and convenience. He is solicitous to know upon what they depend, how they are con nected together, in what respect they resemble each -For this the daring youth Breaks from his weeping mother's fondling arms In foreign climes to rove. The pensive sage, Heedless of sleep, or midnight's hurtful vapour, Hangs o'er the sickly taper. Hence the scorn Of all familiar prospects, though beheld With transport once. Hence th' attentive gaze Of young astonishment. Akenside.

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. 3 Other, and in what they differ. He would discover, if it were possible, whence every thing that he sees originated, by what means it came into existence, and by what peculiar energy it produces those striking phenomena which come under his observation. It is in this desire that the foundation of the science of philosophy is laid, of which it is the professed object to detect the causes of natural appearances, and to trace the connexion between these and their con sequences or effects : a science which is, in fact, co eval with human nature, and which is exhibited in the child as well as in the man ; for the child is as anxious to discover that which occasions the sound of its drum or of its rattle, as the man is to explain the flux and reflux of the tides, or the varying phases of the moon.

But the attainment of success irt this interesting field of discovery, by no means keeps pace with the earnest desire with which it is prosecuted. The real connexions which take place among the ap pearances of nature, and their dependence upon one another, are not to be ascertained without much pa tient inquiry and careful observation. Imagination is but too apt to out-strip the tardy progress of the spirit of investigation, and to substitute in the room of a rational explanation of phenomena, the delusive phantoms of her own visionary suggestions ; and thus it is that the causes assigned for natural appearances, especially in the earlier ages of scientific re search, bear a greater resemblance to the fables of the poet than to the deductions of the sound philosopher. There is, in fact, a strong propensity in the human mind, till chastened by the discipline of science, to* a

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. give the reins to imagination in its inquiries into the constitution of nature. It is powerfully inclined to give life and activity to every thing which it beholds ; to animate the very rocks and stones ; and to hold converse with the winds and waves, as if they understood and sympathised with its feelings. " Savages," says the Abbe Raynal, " wherever they see motion which they cannot account for, there they suppose a soul." It is thus, that a rude people actually ascribe life and activity to the sun, moon, and stars ; that they people the sea and the air, the woods, the rivers, and fountains with imaginary beings, to whose operation they ascribe whatever is wonderful in natural appearances. Thus the sea and river gods, the Dryads, Hamadryads, Naiads, and Nereids, do not owe their existence merely to the poets ; they are the creations of a rude and unskilful philoso phy, which, unable to attain the true explanation of natural phenomena, substitutes those which a lively fancy suggests, and which accord with its own limited experience ; for the most ignorant are aware that changes are really produced by living and active beings ; and they are thence led by a kind of analogical reasoning to infer, that wherever change takes place, there active beings are concerned.

The first suggestions of an unskilful philosophy are soon rejected by succeeding inquirers. The genii of the woods and mountains, the deities of the rivers, winds, and seas, were at an early period aban doned to the poets ; but it was long, very long, be fore explanations of natural appearances more justly suited to the phenomena, occurred to the inquisitive minds of men. It should seem as if scientific inquir-

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. ers were often doomed to exhaust every possible form of error, before they become fortunate enough at length to arrive at the truth. During the cele brated ages of antiquity, so justly distinguished for the high perfection to which the elegant arts and re finements of literature were brought, the science of philosophy made, in fact, but very small advances. Theory succeeded theory, system gave place to system ; each had its supporters, each was ingeniously and strenuously defended ; but each in its turn has sunk into oblivion and neglect. In the present age, the opinions of the various schools of Grecian and Roman philosophy, concerning the causes of natural phenomena, are no longer consulted but as objects of curiosity. The doctrines of Pythagoras, of Plato, of Aristotle, or of Zeno, are equally disregarded, as affording no just interpretation of nature ;„to some of them we give the credit of greater ingenuity than to others ; but to none can we ascribe the honour, which each formerly arrogated to itself, of unveil ing the wonders of the physical and intellectual world, and rendering level to human capacity the mysterious connexions of natural events, and their dependence upon their great and original source.

At length, however, a more just and rational mode of philosophizing has appeared: Bacon was able to point out the errors which before his time per vaded every department of philosophical science, and Newton's transcendent genius furnished the happiest examples of the valuable fruits that might be reaped from the Baconian method of induction. Hypothe sis has been almost banished from science, or at least, from physics ; and sober inquiry and cautious investi-

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. gation have been substituted in its stead. The consequence has been, the attainment of an accuracy and certainty in physical science which former inquirers could hardly have ventured to look for ; while many of the most useful arts of life have been greatly be nefited by the practical application of this science. The philosophy of mind too has participated in the benefits of the Baconian induction, and if its im provements have been later, there is reason to hope, that in the end they may not be less important than those of«physics. It will be acknowledged, however, that much yet remains to be done, in prosecuting the track of dis covery which Bacon and Newton have so successfully opened ; and that even the principles of the Baconian induction have not yet been so completely unfolded and so clearly illustrated, as its great im portance and extensive usefulness appear to demand.

Crude theories both in physics and in metaphysics, are yet too frequently obtruded upon the world, instead of the certain results of a cautious analysis. Inquirers themselves seem often to mistake both the end of scientific investigation, and the means by which alone it can be successfully accomplished. They seem obstinately determined not to relinquish the delusive and fanciful speculations which have so long prevailed to the great detriment of science, concerning vibratory ethers, invisible effluvia, elastic intermedia, and all those hypothetical illusions which obtain currency, solely in consequence of our earnest desire to account for what is unknown, by what we conceive to be better known and more familiar.

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. 7 But, in no respect does the Baconian induction seem more to stand in need of illustration, than in the determination of its proper and precise object. Philosophy, particularly physics, is often called the science of causes ; or it is said to explain the mutual dependence of the phenomena of the material world upon one another, and how the one event proceeds from another, as the effect proceeds from its cause. If, however, we enquire a little more nearly in what this relation of the cause to the effect which it is the object of physical science to explain, actually consists, we shall find it very difficult to give a precise and satisfactory answer to the question. Yet, if the nature of this relation be mistaken, it is obvious that there is the greatest danger of erroneous deduc tions finding their way into physical investigation.

There are few words in our language that have been used with more laxity than the term, cause ; and few in which the attempts at definition have hitherto been attended with so little success. In deed, relations of the most various and even opposite kinds have been occasionally expressed by this term ; so that it is not wonderful that it has given rise to much error and uncertainty. At the same time, it must be acknowledged, that those who are versant in physical speculations have attained a kind of practi cal accuracy in respect to that class of causes which it is their business to investigate, and can in general distinguish them sufficiently well from every other kind of causes. Yet, even in this, many of them have erred ; and it would surely be of the greatest importance to this science that the true nature of its object, viz. the relation of physical causes to their

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. effects, should be pointed out, and the distinction between these and every other kind of causes accu rately defined. In other departments of science, in which the relation between cause and effect is occa sionally an object of examination, the uncertainty of our notions upon the subject has been more se verely felt even than in physics ; and much of the error and absurd speculation which has occasionally disgraced the philosophy of mind, may be distinctly traced to this single source. To ascertain, therefore, the nature of this relation, in as far as it belongs to intellectual science, would certainly be an object of primary importance to that interesting branch of knowledge. It is the purpose of the following' essay, to fix, as far as may be, the limits of those different classes of causes ; and, in particular, to ascertain the real distinction between a physical, and what may be called an intellectual or active cause.

This distinction I have never yet seen clearly and satisfactorily point ed out ; and in many works of established reputation, there are opinions offered upon the subject, which, to me appear highly erroneous and illusory. hi one author who has favoured the world with a confutation of the Necessarjan hypothesis, upon principles which do not admit of refutation, for they are those of mathematical demonstration itself, I have found hints thrown out concerning the rela tion of cause and effect, which prove, that his notions upon this subject, have an accuracy which is not to be met with in any investigation of the question with which I am acquainted. Had he completed the purpose which he there incidentally mentions, of

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. giving to the world his digested thoughts upon the relation in question, any further investigation of that relation, would, I am persuaded, have been superflu ous. But as I know of no likelihood that this in tention will be fulfilled, I am tempted to offer to the world the results of my own inquiry into the sub ject, imperfect as they doubtless are. This merit alone I will venture to arrogate for them, that they are not founded upon any arbitrary hypothesis, but deduced, as far as I have been able, from patient in duction and analytical investigation. In conducting this investigation, I shall endeavour first, to fix the meaning of the term Cause, in as far as it is concerned in our present inquiry ; I shall then take a short review of the principal opinions of philo sophers, both ancient and modern, concerning the relation of cause and effect ; and lastly, I shall endea vour to ascertain in what this relation truly consists, as far as it is an object of precise knowledge, and to point out the difference between those species of it, which, though too often confounded, have yet very opposite qualities. ~.

Chapter I

Of tlw Various Meanings of the Term Cause. r ew circumstances have tended more to retard the progress of genuine science, than the imperfection of language. This important medium of human inter course, as it is invented, and even brought to ma turity at a period of comparative ignorance and bar barism, so it cannot be expected to be naturally possessed of that copiousness and precision which scientific investigation demands. Men invent terms only as they are prompted by occasion and necessity, and they have always shewn themselves strongly inclined, in new cases, rather to make a metaphorical applica tion of the terms of which they are possessed, than to have recourse to the troublesome expedient of en riching the stores of language, by the fabrication of words entirely new. The inevitable consequence is, that in all languages, the greatest number of words are occasionally employed to denote things which differ very essentially from one another ; and there is the greatest danger of men mistaking one another in their discussions and reasonings, if they do not come to an understanding concerning the meaning of those terms which are naturally ambiguous. ch. i. Of the Various Meanings, 8$:. 11 Mr. Locke, in the epistle prefixed to his celebrated Essay upon the Human Understanding, mentions his being present in a company of eminent physi cians, where a learned dispute arose concerning the fluid or liquor with which the nerves are supposed to be furnished.

This dispute was carried on with great ingenuity and animation for a considerable time, and there appeared no prospect of its having an end ; till Mr. Locke proposed that a precise defi nition should be given of the sense in which each person employed the term liquor. No sooner was this complied with, than the dispute immediately ceased ; for the disputants found that they were all of the same opinion. " Many doubts and difficulties," says Dr. Beattie, " have been started about our manner of conceiving identity of person under a change of substance- Plutarch tells us, that in the time of Demetrius Pha lerius, the Athenians still preserved the custom of sending every year to Delos, the same galley, which, about a thousand years before had brought Theseus and his company from Crete ; and that it then used to be a question in the schools, how this could be the same vessel, when every part of its materials had been changed oftener than once.

It is asked, how a tree can be accounted the same, when, from a plant of an inch long, it has grown to the height of fifty feet ; and how identity can be ascribed to the human body, since its parts are continually changing, so that not one particle of the body I now have, belonged to the body I had twenty years ago." (Essay on Truth, Part I. ch. 2. § 3.) b This ingenious philosopher might have added the case of the stockings of the celebrated miser, Sir John Cutler, concerning which, as we are informed by Martinus Scriblerus, precisely the same difficulty was started. They had been originally of worsted, but had been so often dearned with silk, that it became a question whether the stockings were bona fide, silk or worsted stockings/ In such cases, as Dr. Beattie observes, " the difficulties are rather verbal than real.

Was there a single Athenian," asks he, ': who did not know in what respects the galley of Theseus continued the same, and in what respects it was changed? It was the same in respect of its name, its destination, ' its shape, perhaps, and some other particulars ; in respect of its substance, it was altogether different. And when one party in the school maintained that it was the same, and the other that it was not the same, all the difference between them was this, that the one used the word same in one sense, and the others in another.' The identity of vegetables and animals is as easily conceived." Many disputes in matters of science which have been carried on from age to age, without being brought to an issue, have been found in the end to have had no better foundation than the ambiguity of a term ; and would never have existed if the dis putants had set out with, what they were at last obliged to think of, an explanation of the meaning of words.

There is, perhaps, no branch of science, if we except mathematics, that has not occasionally suffered from accidental perplexities of this kind ; and the cause of its exemption is to be found chiefly in the accuracy and precision of its language. Its terms are in a great measure peculiarly its own ; their meaning is always fixed by previous definition ; and, of consequence, they are always employed in a precise determinate sense, so that that kind of sophis try which arises from the ambiguous use of language, can here have no place. In physics there was formerly as much sophistry, as in any branch of knowledge. Those who culti vated it, were divided into numerous sects and par ties, between which, unceasing disputes were carried on, that tended much more to encourage subtility of argument, than to promote the discovery of truth ; and many of which now appear of the most frivo lous nature, being in fact mere verbal contests. — Sects and parties have in a great measure disappear ed in this science, since its principles began to be better understood ; since the objects to which inquiry ought to be directed, were more clearly pointed out ; and since natural philosophers, following the example of mathematicians, have given precision to their technical language, and avoided the use of words in differentand opposite senses.

The science of metaphysics has long suffered se verely from the imperfections, and improper use of words ; and it is indeed, from its very nature, peculiarly exposed to this evil. The attention of men, particularly in a rude state of society, is, of necessity, chiefly occupied by objects of sense ; to these the original terms of language are almost all appropriated ; and, according to the principle already hinted at, when intellectual objects come afterwards to receive names, they are almost invariably denoted by those already allotted to sensible objects, metaphorically applied. It is thus, that we come to speak of a warm heart, of a clear head, or a strong mind ; of under standing, comprehending, or imagining ; all of which are manifest examples of the metaphorical applica tion of the names of the properties of body to intellectual operations.

Thus, in the language of metaphysics, there exists an ambiguity of a very peculiar kind ; and which is necessarily a very copious source of error, on account of the great dissimilarity which there certainly is between the properties of body and those of mind. This ambiguity is the more to be regretted, as per haps no branch of science stands more in need than metaphysics, of terms which are appropriate and distinct. In every other science, the senses are somehow or other concerned ; the naturalist can have recourse to his specimens, the mathematician to his diagrams, and the natural philosopher to his experiments and machinery. But the metaphysi cian has no such expedient by which to give pre cision and certainty to the objects of his investigation. These objects are of the most spiritual and evanescent kind, being nothing else than the various thoughts and feelings of the human mind; their laws, principles, and modes of operation.

It is, therefore, of the greatest consequence that he should be possessed of definitive and accurate terms to give to such airy beings, " a local habitation and a name." * * " The great advantage of the mathematical science above the moral," says Mr Hume, " consists in this, that the ideas of the former being sen sible, are always clear and determinate, the smallest distinction between In this science more than in any other does language become not only a mere vehicle of communi cation, but an important instrument of scientific discovery ; for that it does occasionally play this last dignified part, has been now clearly ascertained by philosophers. " The learned and ingenious Dr. Campbell, in his Philosophy of Rhetoric," says a late celebrated author, " has treated this point (the ambiguity of language) with his usual acuteness and good sense, and has clearly shewn, that a person may not only read, but deliberately write nonsense, without knowing or suspecting it.

The same au thor has very happily illustrated the relation be tween language and thought, by comparing the for mer to the medium, such as water, air, or glass, through which the latter is to be seen ; and to an instrument, such as a mirror, by means of which a person may see even his own thoughts. He remarks, that the utmost possible perfection of such a medium, or such an instrument, is, that it be so them is immediately perceptible, and the same terms are still expressive of the same ideas, without ambiguity or variation. An oval is never mista ken for a circle, nor an hyperbole for an ellipsis. The isosceles and scalenum are distinguished by boundaries more exact than virtue and vice, right and wrong. If any term be defined in geometry, the mind readily, of itself, substitutes on all occasions, the definition for the term defined ; or even when no definition is employed, the object itself may be presented to the senses, and by that means may be steadily and clearly apprehended.

But the finer sentiments of the mind, the operations of the understanding, the various agiations of the passions, though really in themselves distinc^ easily escape us, when surveyed by reflection ; nor is it in our power to re cal the original object, as often as we have occasion to contemplate it. Ambiguity, by this means, is gradually introduced into our reasonings ; similar objects are readily taken to be the same ; and the conclusion be comes at last very wide of the premisses." (Enquiry concerning Humm Understanding, § 7.) clear, that itself shall not be perceived at all, while every thing that should be perceived through it, shall be seen distinctly. He very justly observes, that the terms, clearness, perspicuity, obscurity, so commonly applied to language, denote literally the qualities of such a medium or instrument ; and that they are used metaphorically in their more common application."

" If," adds our author, " the greatest philosopher in the world should obstinately persist in always using a cylindrical mirror, he could never acquire a just notion of his own features, and, in stead of his own face, would see always a very frightful and distorted image ; and, if he chose to view all objects only through green spectacles, he could never distinguish properly their several colours, nor even know the full and varied beauty of the fair face of nature." — " The philosopher who uses in his reasonings, ambiguous and metaphorical ex pressions, which discolour, and distort, and confound every thought which should be seen through them," is,, according to our author, in a very similar situation. (Gregory's Essay on the Relation of Motive and Action, Appendix.) These prefatory remarks on the evils arising from ambiguity of language, especially in metaphysical dis cussion, will not, I hope, be thought superfluous, if it should appear that much of the uncertainty which has prevailed concerning the nature of the relation ' of cause and effect,' has been occasioned by the very vague and indefinite acceptation of the terms.

I scarcely know a word that is employed with greater latitude, and made to denote a greater va riety of relations than the term, cause, and the corresponding terms in other languages. In fact, it is occasionally used to denote almost every kind of de pendence or connexion between events, whether that connexion be real or supposed. Thus, we not only say that impulse is the cause of motion, and that the deity is tlw cause of the existence of the world, which are appropriate applications of the term ; but we say that sickness is caused by anxiety of mind, the fall of a soldier in battle by the mis conduct of his officer, the loss of a ship by the ab sence of the pilot, the belief of a mathematical pro position by its demonstration, the violence of a rob ber by the love of plunder, &c. &c. which are certainly relations of very different and even opposite kinds.

The radical meaning of the word Cause, and of those words which correspond to it in all the lan guages with which I am acquainted, is too indefinite to throw any light upon the precise nature of the re lation usually denoted by a cause. The Latin term causa is by some lexicographers considered as a pri mitive ; by others it is derived from cado, and con sidered as of the same import with casus, chance, accident, or fortune ; and such is the sense implied in the words which denote a cause in the Gothic languages, as I am informed. In French and Italian, the word which denotes cause, and that which sig nifies thing, are evidently derived from the same source. The Greek term for a cause ama., or amov, throws no light upon the subject, as it does not seem to be borrowed from any other root. If causa then originally took its meaning from ca sus, we may, perhaps, best, interpret that meaning c by another word derived from the same root, viz. occasion.