Inquiries concerning the intellectual powers and the investigation of truth

Preface

\ n presenting to the public another Edition of

m volume, the Author feels himself called upon

in to express, in the strongest terms, his sense

he manner in which it has been received, and

he notice which has been bestowed upon it by

I I se whose approbation he highly values. A judice appears to have long existed against ;a^hvsical inquiries, from an impression that

Wfr relate only to scholastic sophistries, incapable )eing applied to any useful purpose, and leading 10 results which are entitled to the character truth. The object of the Author has been to dd all such unprofitable speculations, and to

v fcrict his investigations by those boundaries • hin which the science can be shown to rest a 2 upon authentic facts, and to yield conclusions of the utmost practical importance. If he has thus succeeded in giving to the science of mind some degree of popular interest, the intention is accomplished which he had in view, when he ventured on a course of inquiry, which has been enriched by the talents, and adorned by the eloquence, of some of the most eminent individuals that have devoted themselves to any department of human knowledge.

Contents

PAGE

Introduction . • . . . • • • 1

Preliminary Observations on the General Objects of Science.

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

PAGK

Our Knowledge of Mind limited entirely to Facts . .18

Ideal Theory of the Old Philosophy 19

Of Materialism 21

Grounds for considering Materialism as not only unfounded, but as, in its nature, opposed to the First Principles of Philosophical Inquiry . . . 22 Grounds for believing that the Thinking Principle is, in its Essence, independent of the Body, and will survive it .23 This belief is entirely independent of our Speculations respecting the Immateriality of the Thinking Principle, and rests on a species of evidence altogether different 28

Part II

OF THE ORIGIN OF OUR KNOWLEDGE OF FACTS, RELATING BOTH TO MATTER AND MIND.

Section I. Sensation And Perception

Of the Primary and Secondary Properties of Matter Knowledge of the Properties of Matter by the Senses . Of our Knowledge of Distance and Magnitude Apparent Improvement of some Senses after Loss of others Of our Knowledge of the Nature of Perception.

PAGE

Remarkable Influence of Attention . . - . .43

Habits of Attention and Inattention 44

Of False Perceptions 46

Section II. Consciousness And Reflection

Of the Knowledge which we derive from Consciousness and

1 . The Knowledge of our Mental Processes . . 51

2. Compound Notions, — as Time, Cause, Motion . 52

3. First Truths, or Intuitive Articles of Belief . 52

Section III. Testimony

Rules by which we estimate the Credibility of Testimony . 54 Confidence in Testimony in regard to Statements at Variance

with our Personal Observation or Experience . .56

Objections which have been made to the Reception of such

Statements on the Evidence of Testimony . . . . 57 Fallacy of these Objections, — and Grounds of our Confidence

in Testimony 58

Distinction between Events which are Marvellous and those

which are Miraculous 61

Moral Probability of Miracles . . *. . . .63 Miracles not a Violation of the established Order of Nature,

but referable to an Agency altogether New and Peculiar . 65 Grounds on which we estimate the Credibility of Testimony

in regard to Unusual or Miraculous Events . . . 67

Section I. Memory

Attention

Association

1. Natural or Philosophical Association

2. Local or Incidental Association

3. Arbitrary or Fictitious Association

Artificial Memory

Important Application of the Principle of Arbitrary Association in Commemorative Rites . 92 Conception, or the Memory of Perceptions . . .94

Of the Culture and Improvement of Attention, Reflection,

and Memory 97

Of the Influence of Disease upon Attention and Memory . 103 Of Extensive Cerebral Disease without Sensible Derangement

of the Mental Functions 119

Influence of the Facts connected with this Subject in showing the Independent Existence of the Thinking Principle 130

Section II. Abstraction

Nature and Applications of Abstraction . . .121

Disputes of the Nominalists and Realists . . . . ]-'.)

Section III. Imagination

PAGE

Nature and Applications of Imagination . . .125

Various Kinds of Artificial Combination to which it is

applicable 126

Importance of a proper Application of it in the Formation

of Character . . . . • • • .127

Effects of Fictitious Narrative 128

Effects of an Ill-regulated Imagination .... 129

Section IV. Of Reason Or Judgment

Analysis of the Mental Process of which Reason consists . 131 Applications of Reason in the Investigations of Science, the

Affairs of Common Life, and the Formation of Opinions . 134

Man's Responsibility for his Belief . " . . . 140

Farther Division of the Subject. — Brief Outline of the System

of Dr. Brown 141

§ 1. — OF THE USE OF REASON IN THE INVESTIGATION OF TRUTH.

Of First Truths, or Intuitive Articles of Belief as the Foundation of all Reasoning . . . . , . .143

1. A Belief in our own Existence, and of Mind as

something distinct from the Body . . . 143

2. A Confidence in the Information furnished by our

3. A Confidence in our Mental Operations . . . 145

4. A Belief of our Personal Identity . . .145

X CONTENTS.

PAGE

5. A Conviction that every Event must have a Cause 145

6. A Confidence in the Uniformity of Nature . .146

Uniformity of Physical Relations . .146

Uniformity of Moral Relations . . .149

Application to the question of Liberty and

Necessity 151

Of the Nature and Importance of First Truths, and Sophisms

connected with attempts to reason against them . .158 Laws of Investigation in any Department of Knowledge . 163

1. Of Collecting Facts 165

2. Of Tracing the Relation of Cause and Effect . 166

3. Of Deducing General Principles . . ..166 Of Fallacies in Investigation 168

Fallacies in regard to Facts 168

False Induction . . . . . .168

False Reasoning 169

Of the Nature of Reasoning 169

Of the Syllogism and its uses 170

Of the Cautions in examining a Process of Reasoning or

Investigation 173

Distinction between a Process of Reasoning and a Process of

Investigation 176

Of Fallacies in Reasoning . . . . . . .178

Of Mathematical Reasoning 187

Difference between the sound Exercise of Judgment and the

Art of Disputation 190

Of the Culture and Regulation of the Judgment . . . 1 92

Influence of Attention 192

Prejudice 193

Passion, or State of Moral Feelings . 1 94

Importance of a well-regulated Judgment . . . 1 95

§ 2. — OF THE USE OF REASON IN CORRECTING THE IMPRESSIONS OF THE MIND IN REGARD TO EXTERNAL THINGS.

PAGE

Nature and Effects of this Exercise of Reason . . .196 Peculiar Conditions connected with the Suspension of it . .196

I. DREAMING.

Peculiar Condition of the Mind in Dreaming . 199 Origin of the various Classes of Dreams . .199

1. Recent Events 199

2. Old Associations excited by Bodily Sen-

sations 201

3. Old Associations recalled by a Process of

the Mind itself 204

4. Mental Emotions embodied into Dreams 211 Dreams consist chiefly of Real Objects of Conception 219

Operations of an Intellectual Character in Dreams 22]

II. SOMNAMBULISM.

Various Degrees of this Affection . . . 225 Remarkable Condition commonly called Double

Consciousness 230

III. INSANITY.

Peculiar Condition of the Mind constituting

Various Modifications of it, from Eccentricity to

Mania . 240

Great Activity of the Mental Powers in many

Cases 24 3

Remarkable Loss of Recent Impressions, and

sudden Revival of them on Recovery . .246 Hallucination confined to a Single Point .247

Probable Origin of the Peculiar Hallucinations in

different cases of Insanity . . . . 248

1. Propensities of Character . . . .249

2. Old Associations 249

3. Old Fictions of the Imagination . .249

4. Bodily Feelings 250

5. Undefined Impression of the New and Pecu-

liar Condition of the Mental Powers . 260

Melancholia — Propensity to Suicide . . 251 Origin and Causes of Insanity .... 254 Cautions in deciding on Slight or Suspected Cases 257 Liability of the Insane to Punishment . . . 259 Moral Treatment of Insanity . . . .201 Of Idiocy — Difference between it and Insanity . 266 Cretinism 268

IV. SPECTRAL ILLUSIONS.

Various Forms and Sources of them . . . 274

PAKT IV.

APPLICATION OF THE RULES OF PHILOSOPHICAL INVESTIGATION TO MEDICAL SCIENCE.

PAGE

Uncertainty of Medicine 290

Sources of this Uncertainty 291

1. Difficulty of tracing Effects to their true Causes . 294

2. Intervention of New Causes, which elude our Ob-

servation 295

3. Difficulty in extending our Knowledge to New

Cases, as we must generally act on Analogy, not

on Experience 295

Section IV. Deducing General Facts Or General Principles

Nature of Generalising 315

Difference between Generalising and Classification . ..31 S Rules of Generalising, or of the Induction of General

Principles 319

1. That the Principle be a Fact 319

2. That it be true of all the Individuals . . . 320 Legitimate use of Hypothesis 322

RULES TO BE OBSERVED BY THOSE WHO WOULD CONTRIBUTE

TO THE IMPROVEMENT OF MEDICAL SCIENCE. 325

Part V

VIEW OF THE QUALITIES AND ACQUIREMENTS WHICH CONSTITUTE A WELL-REGULATED MIND.

PAGE

1. Habit of Attention 329

2. Regulation of the Succession of Thoughts . . . 330

3. Activity of Mind 33]

4. Habits of Association and Reflection . . . . 332

5. Proper Selection of Objects of Pursuit . . . 332

6. Government of the Imagination . .. . . . 333

7. Culture and Regulation of the Judgment . . .334

Observing and Inventive Genius . . . . 338

8. Right Condition of the Moral Feelings . . . 340

Introduction

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 assumed a real value and a practical importance, under the researches of those eminent men who have cultivated the philosophy of mind on the principles which are acted upon in physical science, namely, a careful observation of facts, and conclusions drawn from these by the most cautious induction. The chief hinderance to the cultivation of the science on these principles, arises from the difficulty of procuring

B a INTRODUCTION.

the facts. For the only field in which the mental philosopher can pursue his researches with perfect 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 which we meet with in regard to the mental 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 derived in this manner should possess the character of being universal.

The means by which this difficulty can be removed 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 observer. Mental manifestations are greatly modified by the condition of those bodily organs by which the mind holds intercourse with external things, especially the brain. It becomes therefore a matter 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

INTRODUCTION. 3

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 own inquiries. He does not need to be reminded how much the mind acts upon the body, — that mental emotions often prove sources of disease, 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 tranquillised 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 extensive subject. In doing so, I do not profess to offer anything new or original. My object is to present to the younger part of the profession some leading facts, which may serve to direct their further inquiries on a subject of great and general interest.

b 2

I

4 INTRODUCTION.

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 knowledge. 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 attempted 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.

$reltmmatg (©torbatums

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 laws; so that their actions take place in the same manner in every instance in which the same bodies are brought together under similar circumstances. We have a conviction, 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 entirely hidden from us in our present state of being. The province of human knowledge is to observe 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 anything more than incidental juxtaposition. 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, when we meet with some of these events, to expect that certain others are to follow. Hence is excited our idea of power 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 conclude that there is a connexion, whatever may be the nature of it, in consequence of which the sequence which we have observed will continue to recur in the same fixed and uniform manner. In other words, we conclude with confidence, that, when we observe the first of two such events, the second will follow; and that, when we observe the second, the first has preceded it. The first we call cause, the second effect. Thus our general confidence in the uniformity of the true relations or sequences of events is an original or instinctive principle, and not the result of experience ; but it is by experience that we ascertain what the individual sequences are which observe this uniformity; or, in other words, learn to distinguish connexions which consist of incidental contiguity, from those which constitute true and uniform relations.

The natural tendency of the mind appears indeed to be, to infer causation from every succession of phenomena, and to expect uniformity in every sequence. It is from experience we learn that this impression is not to be relied on in regard to individual sequences, but

ORIGIN OF THE IDEA OF CAUSATION. 7

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 farther experience, we have ascertained that the sequence is uniform. This caution, however, has no reference to our instinctive impression of causation, or our absolute conviction that every event must have an adequate cause ; it only relates to our fixing the arrangement of individual antecedents, or, in other words, to our determining what individual events we are warranted in considering as the true antecedents, or causes, of certain other events. This, accordingly, can in many cases be accomplished only by long and extensive observation; while, in others, a single instance may be sufficient to produce an absolute conviction of what is the true antecedent. A child, who has been only once burnt, may dread the fire as certainly as if the accident had happened a hundred times ; and there are many other instances in which the conviction may be produced in the same rapid manner. The natural tendency of the mind, in fact, is not only to infer the 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 similar explosion when be applied a match to other black powders, with the nature of which he was unacquainted, such as powdered charcoal. It is by experience that this erroneous expectation would be corrected, and that he would learn the precise instances in which

O GENERAL OBJECTS OF SCIENCE.

the particular result takes place. But it is also by experience or observation that he learns the former, though the conviction was produced more immediately ; for there is nothing in 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 remain entirely unchanged.

Thus, our general impression of causation is not the result of experience, but an original and intuitive principle of belief; that is, our absolute conviction, that every event must have an adequate cause. This is, in fact, that great and fundamental truth, by which from the properties of a known effect, we infer the powers and qualities of an unknown cause. It is in this manner, for example, that from the works of nature we infer the existence and 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 anything in our present state of being. "We know that the application of a match always sets fire to gunpowder ; and we say, that it has the power of doing so, or that it is the cause of the explosion ; but we have not the least conception why the application of fire produces combustion in an inflammable substance, — these expressions, therefore, amount to nothing more than a statement of the fact, that the result is universal.

When we • speak, therefore, of physical causes, in regard to any of the phenomena of nature, we mean nothing more than the fact of a certain uniform connexion which has been observed between events. Of

CAUSATION. y

efficient causes, or the manner in which the result takes place, we know nothing. In this sense, indeed, we maybe said not to know the cause of anything, even of events which at first sight appear the most simple and obvious. Thus the communication of motion from one body to another by impulse appears a very simple phenomenon, — but how little idea have we of the cause of it. We say the bodies touch each other, and so the motion is communicated. But, in the first place, we cannot say why a body in motion, coming in contact with one at rest, should put the latter in motion ; and farther, we know that they do not come in contact. We may consider it, indeed, as ascertained, and 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 us. Why, for example, one medicine acts upon the stomach, another on the bowels, a third on the kidneys, a fourth on the skin, we have not the smallest conception ; we know only the uniformity of the facts.

It is of importance to keep in mind the distinction now referred to between physical and efficient causes, as the former only are the proper objects of philosophical inquiry. The term final cause, again, has been applied to a subject entirely different; namely, to the appearances of unity of design in the phenomena of nature, and the manner in which means are adapted to particular ends. The subject is one of great and extensive importance, but it appears desirable that the name were altered, though it is sanctioned by high authority ; for, when viewed in connexion with the sense in which the word cause is employed in modern science, it expresses a meaning remarkably different. The investigation to which it refers is also of a distinct nature, though one of the highest interest. It leads us chiefly to the inductions of natural religion respecting a great and intelligent First Cause ; but it may also be directed to the discovery of truth in regard to the phenomena of nature. One of the most remarkable examples of this last application of it is to be found in the manner in which Harvey was led to the discovery of the circulation of the blood, by observing the valves in the veins, and contemplating the uses to which 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 followed by certain other events ; in other words, the aptitude of certain bodies to produce, or to be followed by, certain changes in other bodies in particular circumstances. The object of art is to avail ourselves of the knowledge thus acquired, by bringing bodies into such circumstances as are calculated to lead to those actions upon each other of which we have ascertained them to be capable. Art, therefore, or the production of certain results by the action of bodies upon each other, must be founded upon science, or a knowledge of their fixed and uniform relations and tendencies. This principle applies to all sciences, and to the arts or practical rules which are founded upon them; and the various sciences differ only in the particular substances or events which are their more immediate objects.

In the physical sciences, we investigate the relations of material substances, and their actions upon each other, either of a mechanical or chemical nature. On the relations thus ascertained are founded the mechanical and chemical arts, in which we produce certain results, by bringing bodies into such circumstances as are calculated to give rise to their peculiar actions. But mental phenomena have also their relations, which are likewise

DISTINCTION OF SCIENCES AND AKTS. 11

fixed and uniform; though it may be more difficult to ascertain the truth in regard to them, than in the relations of material things.

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

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

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

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

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

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

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

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

In medical science, the objects of our researches are chiefly the relations between external things and the living powers of animal bodies, — and the relations of these powers to each other ; — more particularly in regard to the tendencies of external things to produce certain changes upon living bodies, either as causes of di~ or as remedies. The practical art founded upon this science leads to the consideration of the means by which we may avail ourselves of this knowledge, by producing, in the one case, actions upon the body which we wish to

UNIFOEMITY OF KELATIONS. 13