Inquiries concerning the Intellectual Powers and the Investigation of Truth ... Second edition

Preface

TO THE SECOND EDITION. The Author deeply feels the favourable manner in which this volume has been received by the public, and the notice which has been bestowed upon it by those whose approbation is high praise. In preparing a new edition, he has made various verbal corrections, and has added a considerable number of new facts and observations, which, he trusts, may increase the interest of the work. Some of these additions will be found under the following subjects : — The question of the immateriality of the thinking principle ; — false perceptions ; — the credibility of testimony ; — memory ; — conception ; — and the influence of disease upon attention and memory. There are also various new facts on dreaming and spectral illusions ; and, under the section " on the qualities and acquire-

PREFACE.

. ments which constitute a well regulated mind," there have been added remarks on Observing and Inventive Genius. Edinburgh, August, 1831. THIRD EDITION. In the Third Edition, various new facts have been added : the most important of them are two remarkable cases of Somnambulism at pages 296, and 300. July, 1832- CONTENTS. Page Introduction ..... 1 Preliminary Observations on the General Objects of Science. Uniformity of the Relations of Bodies . . 5 Origin of our Idea of Causation . . 6 Our Idea of the Relation of Cause and Effect, in reference to any two events, entirely distinct from our intuitive impression of Causation . . 7 Of Physical, Efficient, and Final Causes . . 10 The Object of Science is to trace the Uniform Relations of things .... 12 The Object of Art is to apply our Knowledge of these relations, for producing particular results ib.

Distinction of Sciences and Arts, according to the particular substances or relations which are their immediate objects . . .ib. Division of Sciences into Certain and Uncertain 16 Grounds of uncertainty in a Science . . 17 Illustrations of the Uncertain Sciences from Medicine and Political Economy . . 19 Imperfection of all Science, from the limited nature of the human faculties ... VI CONTENTS,

Part I. Of The Nature And Extent Of Our Knowledge Of Mind

Our knowledge of mind limited entirely to Facts . 23 Ideal Theory of the Old Philosophy . 24 Of Materialism ..... 27 Grounds for considering Materialism as not only unfounded, but as, in its nature, opposed to the First Principles of Philosophical Inquiry . . 28 Grounds for believing that the Thinking Principle is, in its Essence, independent of the Body, and will survive it ... . . .29 This belief is entirely independent of our speculations respecting the immateriality of the thinking principle, and rests on a species of evidence altogether different ..... 35

Section I. Sensation And Perception

42 Of the Primary and Secondary properties of Matter 43 Knowledge of the properties of Matter by the Senses 44 Of our Knowledge of Distance and Magnitude . 47 Apparent improvement of some Senses after loss of others 51 Of our Knowledge of the Nature of Perception . . 54 Remarkable influence of Attention . 56 Habits of Attention and Inattention . 57 jOf False Perceptions . . .60 CONTENTS. VII

Section II. Consciousness And Reflection

Of the Knowledge which we derive from Consciousness and Reflection ... 67 1. The Knowledge of our Mental Processes . 68 2. Compound Notions, — as Time, Cause, Motion ib. 3. First truths, or Intuitive Articles of Belief . 69

Section III. Testimony

Rules by which we estimate the Credibility of Testimony 71 Confidence in Testimony in regard to statements at variance with our Personal Observation or Experience 74 Objections which have been made to the Reception cf such Statements on the Evidence of Testimony . . 75 Fallacy of these Objections, — and Grounds of our Confidence in Testimony ... .76 Distinction between Events which are Marvellous and those which are Miraculous . . . 81 Moral Probability of Miracles ... 82 Miracles not a violation of the established order of Nature, but referable to an agency altogether new and peculiar 85 Grounds on which we estimate the Credibility of Testimony in regard to unusual or miraculous events . CONTENTS. VIII 93

Part III. Of The Intellectual Operations Section

I. MEMORY . . 96 Attention ...... 98 Association . . . . . .102 1. Natural or Philosophical Association . . 107 2. Local or Incidental Association . . 112 3. Arbitrary or Fictitious Association . . 118 Artificial Memory . . . 119 Important Application of the Principle of Arbitrary Association in Commemorative Rites . . . 121 Conception, or the Memory of Perceptions . . 123 Of the Culture and Improvement of Attention, Reflection, and Memory .... 127 Of the Influence of Disease upon Attention and Memory 135 Of Extensive Cerebral Disease, without Sensible Derangement of the Mental Functions . . 152 Influence of the Facts connected with this Subject in shewing the Independent Existence of the Thinking Principle . . . CONTENTS. IX

SECTION II. ABSTRACTION.

Nature and Applications of Abstraction . . 155 Disputes of the Nominalists and Realists . . 157

SECTION III. IMAGINATION.

Nature and Applications of Imagination . . 160 Various Kinds of Artificial Combination to which it is applicable . . . . . • 161 Importance of a Proper Application of it in the Formation of Character . . . . .163 Effects of Fictitious Narrative . . . 1 64 Effects of an Ill-regulated Imagination . . 1 65

Section IV. Reason Or Judgment

Analysis of the Mental Process of which Reason consists 168 Applications of Reason in the Investigations of Science, the Affairs of Common Life, and the Formation of Opinions . . . . . .173 Man's Responsibility for his Belief . . . 179 Farther Division of the Subject — Brief Outline of the System of Dr. Brown .... X CONTENTS. § I. OF the use of reason in the investigation OF TRUTH. Of First Truths, or Intuitive Articles of Belief, as the Foundation of all Reasoning . . . 184 1. A Belief in our own Existence, and of Mind as something distinct from the Body . 184 2. A Confidence in the Information furnished by our Senses . . . . 185 3. A Confidence in our Mental Operations 186 4. A Belief of our Personal Identity . 1S6 5. A Conviction that every Event must have a Cause .... 187 6. A Confidence in the Uniformity of Nature 187 Uniformity of Physical Relations . 188 Uniformity of Moral Relations . . 191 Application to the question of Liberty and Necessity . . 195 Of tbe Nature and Importance of First Truths, and Sophisms connected with attempts to reason against them 204 Laws of Investigation in any Department of Knowledge 210 1.

Of Collecting Facts . . . 214 2. Of Tracing the Relation of Cause and Effect 214 3. Of Deducing General Principles . 215 Of Fallacies in Investigation . . . 216 Fallacies in regard to Facts . . 217 False Induction . . . . 217 False Reasoning . . • 218 Of the Nature of Reasoning . . 218 Of the Syllogism and its Uses . . 220 Of the Cautions in examining a Process of Reasoning or Investigation . . . CONTENTS. XI Distinction between a process of Reasoning, and a process of Investigation . . 227 Of Fallacies in Reasoning . . 230 Of Mathematical Reasoning . . 242 Difference between the sound Exercise of Judgment and the Art of Disputation . . 246 Of the Culture and Regulation of the Judgment 249 Influence of Attention . . 249 — — — Prejudice . . . 250 . Passion, or State of Moral Feelings 251 Importance of a well regulated Judgment . 251 § II of the use of reason in correcting THE IMPRESSIONS OF THE MIND IN REGARD TO EXTERNAL THINGS.

Nature and Effects of this Exercise of Reason . 253 Peculiar Conditions connected with the Suspension of it 255 I. DREAMING . . 258 Peculiar Condition of the Mind in Dreaming 258 Origin of the Various Classes of Dreams. 1. Recent Events p . . 258 2. Old Associations excited by Bodily Sensations . . 260 3. Old Associations recalled by a Process of the Mind itself . . 265 4. Mental Emotions embodied into Dreams 273 Dreams consist chiefly of Real Objects of Conception . . 2S1 Operations of an Intellectual Character in Dreams CONTENTS. XII II. SOMNAMBULISM. Various degrees of this Affection . . 288 Remarkable Condition commonly called double Consciousness . . 294 III. ivSANITY. Peculiar Condition of the Mind constituting Insanity . . 306 Various Modifications of it, from Eccentricity to Mania ... 307 Great Activity of the Mental Powers in many Cases . . .310 Remarkable Loss of Recent Impressions and sudden revival of them on Recovery 314 Hallucination confined to a single Point 316 Probable Origin of the peculiar Hallucinations in different cases of Insanity . 318 1.

Propensities of Character . 318 2. Old Associations . . 318 3. Old Fictions of the Imagination » 319 4. Bodily Feelings . . 319 5. Undefined Impression of the New and Peculiar Condition of the Mental Powers . . 320 Melancholia — Propensity to Suicide . 321 Origin and Causes of Insanity . 325 Cautions in deciding on slight or suspected cases 329 Liability of the Insane to Punishment . 331 Moral Treatment of Insanity . 334 Of Idiocy — Difference between it and Insanity 340 Cretinism . . . 343 IV- SPECTRAL ILLUSIONS. Various Forms and Sources of them . CONTENTS. XIII

Part IV. Application Of The Rules Of Philosophical Investigation To Medical Science

Uncertainty of Medicine . . 368 Sources of this Uncertainty . . 373 I. Difficulty of tracing Effects to their true Causes 373 2. Intervention of New Causes, which elude our Observation . . 374 3. Difficulty in extending our Knowledge to New Cases, — as we must generally act on Analogy, not on Experience . . 375

Section IV. Deducing General Facts Or General Principles

Nature of Generalizing .... 402 Difference between Generalizing and Classification CONTENTS. XV Rules of Generalizing, or of the Induction of General Principles ..... 408 1. That the Principle be a Fact . . 408 2. That it be true of all the Individuals . 409 Legitimate Use of Hypothesis . . y . 412 I RULES TO BE OBSERVED BY THOSE WHO WOULD CONTRI- BUTE TO THE IMPROVEMENT OF MEDICAL SCIENCE 415

Part V. View Of The Qualities And Acquirements Which Constitute

A WELL REGULATED MIND. I. Habit of Attention . . . 421 2. Regulation of the Succession of Thoughts 422 3. Activity of Mind . . . 425 4. Habits of Association and Reflection . 425 5. Proper selection of Objects of pursuit . 425 6. Government of the Imagination . 425 7. Culture and Regulation of the Judgment 427 Observing and Inventive Genius . 433 8. Right condition of the Moral Feelings .

Introduction

. In entering upon the following Essay, I find it ne cessary to offer some explanation of the views which induce me to attempt a subject so foreign to those inquiries by which I am in some measure known to the public, and in which they have been pleased to receive my researches in the most favourable manner. The study of the phenomena of mind presents a subject of intense interest, not to the moral philosopher only, but to every one who has in view the cultivation of his own mental powers, or the proper application of them to the investigation of truth in any department of knowledge. During the prevalence of that system which has been called the Metaphysics of the Schools, this important inquiry was obscured by speculations of the most frivolous nature. It is in modern times only that it has as sumed a real value and a practical importance, under the researches of those eminent men, who B

INTRODUCTION.

. have cultivated the philosophy of mind on the principles which are acted upon in physical science, namely, a careful observation of facts, and conclu sions drawn from these by the most cautious induction. The chief hinderance to the cultivation of the science \m these principles, arises from the diffi culty of procuring the facts. For the field, in which the mental philosopher can pursue his researches with greatest confidence, is his own mind. In his observations on the minds of other men, he is obliged to judge of the internal operations by external phenomena ; and in this manner a degree of uncertainty attends his investigations, which does not occur in physical science. From this source, also, has probably arisen much of that difference of opinion Avhich Ave meet with in regard to the men tal powers : For, each inquirer having drawn his observations chiefly from one mind, namely, his own, it was scarcely to be expected that there should not be some diversity, or that facts deriv-ed in this manner should possess the character of being universal.

The means by which this difficulty can be re moved must consist in an extensive collection of facts, illustrating the phenomena of mind in various individuals, and under a variety of circumstances ; and there are several points of view in which the subject is peculiarly adapted to the medical ob server. Mental manifestations are greatly modified by the condition of those bodily organs by which the mind holds intercourse with external things,

INTRODUCTION.

. 3 especially the brain. It becomes therefore a mat ter of the greatest interest, to ascertain the manner in which the manifestations of mind are affected by diseases of these organs, as well as to observe their condition in that remarkable class of affections, commonly called diseases of the mind. Besides, in the affections which are referable to both these classes, we often meet with manifestations of the most interesting kind, and such as are calculated to illustrate, in a very striking manner, important points in the philosophy of the mental powers. It is thus in the power of the observing physician to contribute valuable facts to the science of mind ; and it is almost unnecessary to add, that the study may be turned to purposes of immediate importance to his OAvn inquiries. He does not need to be re minded, how much the mind acts upon the body that mental emotions often prove sources of dis ease, or causes by which his remedies are modified or counteracted — and that, on the other hand, a remedy may often be introduced by the mind, capable of composing tumults of the corporeal functions, which cannot be tranquillized by physical aid.

From the deep interest which the philosophy of mind thus presents to the medical inquirer, I have been induced to attempt a slight outline of this ex tensive subject. In doing so, I do not profess to offer any thing new or original. My object is to present to the younger part of the profession some leading facts, which may serve to direct their fari.

INTRODUCTION.

. ther inquiries on a subject of great and general in terest. This slight outline of the functions of mind will be^followed by an attempt to trace the rules, which ought to guide us in applying these powers to the investigation of truth, in any department of know ledge. The practical application of the subject will lead to a general view of the laws or principles of philosophical inquiry and inductive science, and will then be directed in a more particular manner to the purposes of medical investigation. This is at tempted in the hope that the principles which it is meant to convey, may be of use in giving precision to medical investigations, by illustrating those rules of sound induction, which are acted upon in other departments of science. PRELIMINARY OBSERVATIONS ON THE GENERAL NATURE AND OBJECTS OF SCIENCE.

By the will of the Almighty Creator, all things in nature have been placed in certain relations to each other, which are fixed and uniform. In other words, they have been endowed with capacities of acting, and capabilities of being acted upon, according to certain uniform laAvs ; so that their ac tions take place in the same manner in every in stance in which the same bodies are. brought toge ther under similar circumstances. We have a con viction, which appears to be original and instinctive, of the general uniformity of these relations ; and in this consists our confidence in the regularity of all the operations of nature. But the powers or principles on which the relations depend are en tirely hidden from us in our present state of being. The province of human knowledge is merely to ob serve the facts, and to trace what their relations or sequences are.

This is to be accomplished only by a careful and extensive observation of the facts as they pass before us, and by carefully distinguishing their true or uniform relations, from connexions which are only incidental and temporary. In our first observation of any particular series of facts or events, we find a certain number of them placed together in a state of contiguity or apparent connexion. But we are not entitled from this to assume the connexion to be any thing more than incidental juxta-position. When, in the farther progress of observation, we find the same events occurring a certain number of times, in the same relations or sequences to each other, we suspect that their connexion is not merely that of incidental contiguity. We begin to believe that there exists among them such a relation, as leads us, Avhen we meet with some of these events, to expect that certain others are to follow.

Hence is excited our idea of poAver in reference to these events, or of the relation of cause and effect. This relation, however, according to the utmost extent of our knowledge of it in any individual instance, is founded entirely upon the fact of certain events uniformly following one another. But, when we have found, by sufficient observation, the particular events which do thus follow one another, we con clude that there is a connexion, whatever may be the nature of it, in consequence of which the se quence which we have observed will continue to recur in the same fixed and uniform manner. In other words, we conclude with confidence, that, ORIGIN OF THE IDEA OF CAUSATION. 7 Avhen we observe the first of two such events, the second will follow ; and that, when we observe the second, the first has preceded it.

The first we call cause, the second effect. Thus our general confidence in the uniformity of the true relations or se quences of events is an original or instinctive prin ciple, and not the result of experience ; but it is by experience that we ascertain Avhat the individual se quences are which observe this uniformity ; or, in other words, learn to distinguish connexions Avhich consist of incidental contiguity, from those which constitute true and uniform relations. The natural tendency of the mind appears in deed to be, to infer causation from every succession of phenomena, and to expect uniformity in every sequence. It is from experience we learn, that this impression is not to be relied on in regard to individual sequences, but requires to be corrected by observation. The result of our farther experience then is, to ascertain what those sequences are which are uniform, and which, consequently, we may consider as connected in the manner of causation.

We are thus first taught by experience the caution which is necessary in considering events as connected in the manner of cause and effect ; and learn not to assume this relation, till, by far ther experience, we have ascertained that the se quence is uniform. This caution, however, has no reference to our instinctive impression of causation, or our absolute conviction that every event must have an adequate cause ; it only relates to our fixing the arrangement of individual antecedents, or, in other words, to our determining Avhat individual events we are warranted in considering as the true antecedents or causes of certain other events. This, accordingly, can in many cases be accomplished only by long and extensive observation ; while, in others, a single instance may be sufficient to pro duce an absolute conviction of what is the true ante cedent.

A child, who has been only once burnt, may dread the fire as certainly as if the accident had happened an hundred times -, and there are many other instances in which the conviction may be produced in the same rapid manner. The natural tendency of the mind, in fact, is not only to in fer the connexion, but in many cases to carry it farther than the truth. If, for instance, we suppose a man, who, for the first time in his life, has seen gunpowder explode upon a match being applied to it, — he would probably have an immediate conviction that a similar explosion would take place again in similar circumstances. But he would perhaps go farther than this : he would probably expect a si milar explosion when he applied a match to other black powders, with the nature of which he was un acquainted, such as powdered charcoal.

It is by experience that this erroneous expectation would be corrected, and that he would learn the precise instances in which the particular result takes place. But it is also by experience or observation that he learns the former, though the conviction was pro duced more immediately ; for there is nothing in CAUSATION. 9 the characters of gunpowder and charcoal from which any man could pronounce, by reasoning a priori, that the one would explode with violence when a match was applied to it, and the other re main entirely unchanged. Thus, our general impression of causation is not the result of experience, but an original and intuitive principle of belief; that is, our absolute con viction, that every event must have an adequate cause. This is, in fact, that great and fundamental truth, by which, from the properties of a known effect, we infer the powers and qualities of an un known cause.

It is in this manner, for example, that from the works of nature we infer the exis tence and the attributes of the Almighty Creator. But, in judging of the connexion between any two individual events in that order of things which he has established, our idea of causation is derived from experience alone. For, in regard to any two such events, our idea of causation or of power amounts to nothing more than our knowledge of the fact, that the one is invariably the antecedent of the other. Of the mysterious agency on which the connexion depends, we know nothing, and never can know any thing in our present state of being. We know that the application of a match always sets fire to gunpowder, and we say, that it has the power of doing so, or that it is the cause of the explosion ; but we have not the least conception why the application of fire produces combus tion in an inflammable substance ; — these expressions, therefore, amount to nothing more than a statement of the fact, that the result is universal.

When we speak, therefore, of physical causes, in regard to any of the phenomena of nature, we mean nothing more than the fact of a certain uniform connexion which has been observed betAveen events. Of efficient causes, or the manner in which the result takes place, Ave know nothing. In this sense, indeed, we may be said not to know the cause of any thing, even of events which at first sight ap pear the most simple and obvious. Thus, the communication of motion from one body to ano ther by impulse appears a very simple phenome non, — but how little idea have we of the cause of it ! We say the bodies touch each other, and so the motion is communicated. But, in the first place, we cannot say why a body in motion, com ing in contact with one at rest, should put the lat ter in motion ; and farther, we know that they do not come in contact.

We may consider it, indeed, as ascertained, that there is no such thing as the actual contact of bodies under these circumstances ; and therefore, the fact which appears so simple comes to be as unaccountable as any phenomenon in nature. What, again, appears more intelligible than an unsupported body falling to the ground ? Yet, what is more inexplicable, than that one mass of matter should thus act upon another, at any distance, and even though a vacuum be interposed between them ? The same observation will be seen to apply to all the facts which are most familiar to PHYSICAL, EFFICIENT AND FINAL CAUSES. Us. Why, for example, one medicine acts upon the stomach, another on the bowels, a third on the kidneys, a fourth on the skin, we have not the smallest conception ; we know only the uniformity of the facts.

It is of importance to keep in mind the distinction now referred to betAveen physical and efficient causes, as the former only are the proper ob jects of philosophical inquiry. The term final cause, again, has been applied to a subject entirely different ; namely, to the appearances of unity of design in the phenomena of nature, and the man ner in which means are adapted to particular ends. The subject is one of great and extensive impor tance, but it appears desirable that the name were altered, though it is sanctioned by high authority ; for, when viewed in connexion with the sense in Avhich the word cause is employed in modern science, it expresses a meaning remarkably different. The investigation to which it refers is also of a distinct nature, though one of the highest inter est. It leads us chiefly to the inductions of natural religion respecting a great and intelligent first cause ; but it may also be directed to the discovery of truth in regard to the phenomena of nature.

One of the most remarkable examples of this last application of it is to be found in the manner in which Harvey was led to the discovery of the cir culation of the blood, by observing the valves in the veins, and contemplating the uses to Avhich that peculiar structure might be adapted. The object of all science is to ascertain these established relations of things, or the tendency of certain events to be uniformly folloAved by certain other events ; in other words, the aptitude of cer tain bodies to produce, or to be followed by, certain changes in other bodies in particular circumstances. The object of art is to avail ourselves of the knowledge thus acquired, by bringing bodies into such circumstances as are calculated to lead to those actions upon each other of which Ave have ascertained them to be capable.

Art, therefore, or the production of certain results by the action of bodies upon each other, must be founded upon science, or a knoAvledge of their fixed and uniform relations and tendencies. This principle applies to all sciences, and to the arts or practical rules which are founded upon them ; and the various sciences differ only in the particular substances or events which are their more immediate objects. In the physical sciences, Ave investigate the relations of material substances, and their actions upon each other, either of a mechanical or chemical nature. On the relations thus ascertained are founded the mechanical and chemical arts, in which we produce certain results by bringing bodies into such circumstances as are calculated to give rise to their peculiar actions. But mental phenomena have also their relations, which are likewise fixed and uniform ; though it may be more difficult to ascertain the truth in regard to them, than in the relations of material things.

UNIFORMITY OF RELATIONS. 13 The relations or sequences of mental phenome na are to be considered in two points of view, namely, relations to each other and relations to ex ternal things. In regard to both, it seems necessary to divide the phenomena themselves into three classes. 1. Simple intellect, or those powers by which we perceive, remember, and combine facts or events, and compare them with each other : such as perception, memory, imagination, and judgment. 2. Passive emotions, or those by which the mind is affected by certain pleasurable or painful feelings, which are, or may be, confined entirely to the in dividual who is the subject of them. 3. Active emotions, or those which tend directly to influence the conduct of men, either as moral and responsible beings, or as members of society.

In all these classes, mental phenomena have cer tain relations to each other and to external things, the investigation of which is the object of particular branches of science ; and these lead to certain arts or practical rules which are founded upon them. Intellectual science investigates the laws and relations of the processes of simple intellect, as perception, memory, imagination and judgment ; and the proper cultivation and regulation of these is the object of the practical art of intellectual edu cation. The passive emotions may be influenced or ex cited in two ways ; — namely — through our relations to other sentient and intelligent beings, — and by material or inanimate things. To the for mer head are referable many of the tenderest and most interesting feelings of our nature, as love, hope, joy, and sorrow.

To the latter belong those emotions which come under the subject of taste, or the tendencies of certain combinations of material things to excite emotions of a pleasurable or painful kind, — as our impressions of the sublime, the beautiful, the terrible, or the ludicrous. The practical rules or processes, connected with the science of the passive emotions, arrange themselves into two classes, corresponding to the two divisions now mentioned. To the former belong the regulation of the emotions, and all those rules of conduct not exactly referable to the higher subject of morals, which bear an extensive influence on the ties of friendship, and the relations of social and domestic intercourse. To the latter belong chiefly those processes which come under the head of the fine arts ; — namely, the arts of the painter — the sculp tor — the architect — the musician ; perhaps we may add, the poet and the dramatist.