The inspiration of the Almighty giveth them understanding. — Jab.
LONDON: PRINTED FOR THOMAS TEGG, CHEAPSIDE; (i. AND J. ROBINSON; G. OFFOR; AND J. EVANS AM) CO. I ALSO, R. GRIFFIN AND CO. GLASGOW; AND J. CUMMING, UL'BLIN.
LIBRARY UNIVERSITY OF CALIFORNIA gANTA BARBARA CONTENTS.
CHAP. I.
INTRODUCTION.
Sect. P»g« 1. THE Importance of the Subject, and the Means of prosecuting it 1 2. The Impediments to our Knowledge of the Mind. 3 3. The present State of this Part of Philosophy. Of Des Cartes, Malebranche, and Locke...7 4. Apology for those Philosophers 10 5. Of Bishop Berkeley — the Treatise of Human Nature — and of Scepticism 12 6. Of the Treatise of Human Nature 14 7. The System of all these Authors is the same, and leads to Scepticism 16 8. We ought not to despair of a better 17 CHAP. II.
OF SMELLING.
1. The Order of Proceeding. Of the Medium and Organ of Smell 19 2. The Sensation considered abstractly...20 3. Sensation and Remembrance natural Principles of iv CONTENTS.
.Sect. Page 4. Judgment and Belief in some Cases precede simple Apprehension 24 5. Two Theories of the Nature of Belief refuted.
Conclusions from what hath been said...25 6. Apology for metaphysical Absurdities. Sensations without a Sentient, a Consequence of the Theory of Ideas. Consequences of this strange Opinion 28 7. The Conception and Belief of a sentient Being, or Mind, is suggested by our Constitution. The Notion of Relations not always got by com- paring the related Ideas 33 8. There is a Quality or Virtue in Bodies, which we call their Smell. How this is connected in the Imagination with the Sensation...36 O 9. That there is a Principle in Human Nature, from which the Notion of this, as well as all other natural Virtues or Causes, is derived...38 10. Whether in Sensation the Mind is active or passive? 43 CHAP. III.
OF TASTING 45 CHAP. IV.
OF HEARING.
1. Variety of Sounds. Their Place and Distance learned by Custom, without Reasoning.. 49 2. Of natural Language 51 CONTENTS. V CHAP. V.
OF TOUCH.
Sect. > Page 1. Of Heat and Cold. 55 2. Of Hardness and Softness 57 3. Of Natural Signs 61 4. Of Hardness and other primary Qualities...64 5. Of Extension 66 6. Of Extension 69 J7. Of the Existence of a material World...72 8. Of the Systems of Philosophers concerning the Senses 79 CHAP. VI.
OF SEEING.
1. The Excellence and Dignity of this Faculty.. 84 2. Sight discovers almost nothing which the Blind may not comprehend. The Reason of this. 86 3. Of the visible Appearance of Objects...91 4. That Colour is a Quality of Bodies, not a Sensation of the Mind 94 5. An Inference from the preceding 97 6. That none of our Sensations are Resemblances of any of the Qualities of Bodies 101 7. Of visible Figure and Extension 107 8. Some Queries concerning visible Figure answered Ill • 9. Of the Geometry of Visibles 117 10. Of the parallel Motion of the Eyes...128 11. Of our seeing Objects erect by inverted Images. 132 12. The same Subject continued 138 A2 VI CONTENTS.
Sect. pgge 13. Of seeing Objects single with Two Eyes...153 14. Of the Laws of Vision in brute Animals...161 1-5. Squinting considered hypothetically...164 1 6. Facts relating to Squinting 175 17. Of the Effect of Custom in seeing Objects single 178 18. Of Dr. Porterfield's Account of single and double Vision 185 19. Of Dr. Briggs's Theory, and Sir Isaac Newton's Conjecture on this Subject 189 20. Of Perception in general 199- •21. Of the Process of Nature in Perception...207 22. Of the Signs by which we learn to perceive Distance from the Eye 213 23. Of the Signs used in other acquired Perceptions 224 24. Of the Analogy between Perception and the Credit we give to Human Testimony...227 CHAP. VII.
CONCLUSION.
Containing Reflections upon the Opinions of Philo- sophers on this Subject 244 TO THE RIGHT HONOURABLE JAMES, EARL OF FINDLATER AND SEAFIELD, CHANCELLOR OF THE UNIVERSITY OF OLD ABERDEEN.
MY LORD, THOUGH I apprehend that there are things new, and of some importance, in the following Inquiry, it is not without timidity that I have consented to the publica- tion of it. The subject has been canvased by men of very great penetration and genius: for who does not acknowledge Des Cartes, Malebranche, Locke, Berke- ley, and Hume, to be such? A view of the human understanding, so different from that which they have exhibited, will, no doubt, be condemned by many without examination, as proceeding from temerity and vanity.
But I hope the candid and discerning Few, who are capable of attending to the operations of their own minds, will weigh deliberately what is here advanced, Vlll DEDICATION.
before they pass sentence upon it. To such I appeal, as the only competent judges. If they disapprove, I am probably in the wrong, and shall be ready to change my opinion upon conviction. If they approve, the Many will at least yield to their authority, as they always do.
However contrary my notions are to those of the writers I have mentioned, their speculations have been of great use to me, and seem even to point out the road which I have taken: and your Lordship knows, that the merit of useful discoveries is sometimes not more justly due to those that have hit upon them, than to others that have ripened them, and brought them to the birth.
I acknowledge, my Lord, that I never thought of calling in question the principles commonly received with regard to the human understanding, until the Treatise of Human Nature was published in the year 1739. The ingenious author of that treatise, upon the principles of Locke, who was no sceptic, hath built a system of scepticism, which leaves no ground to be- lieve any one thing rather than its contrary. His rea- soning appears to me to be just: there "was therefore a necessity to call in question the principles upon which it was founded, or to admit the conclusion.
But can any ingenuous mind admit this sceptical system without reluctance? I truly could not, my Lord: for I am persuaded, that absolute scepticism is not more destructive of the faith of a Christian than of DEDICATION. IX the science of a philosopher, and of the prudence of a man of common understanding. I am persuaded that the unjust live by faith as well as the just; that, if all belief could be laid aside, piety, patriotism, friendship, parental affection, and private virtue, would appear as ridiculous as knight-errantry; and that the pursuits of pleasure, of ambition, and of avarice, must be grounded upon belief, as well as those that are honourable or vir- tuous.
The day-labourer toils at his work, in the belief that he shall receive his wages at night; and if he had not this belief, he would not toil. We may venture to say, that even the author of this sceptical system wrote it in the belief that it should be read and regarded. I hope he wrote it in the belief also, that it would be useful to mankind: and perhaps it may prove so at last. For I conceive the sceptical writers to be a set of men, whose business it is to pick holes in. the fabric of knowledge wherever it is weak and faulty; and when these places are properly repaired, the whole building becomes more firm and solid than it was formerly.
For my own satisfaction, 1 entered into a serious examination of the principles upon which this sceptical system is built; and was not a little surprised to find that it leans with its whole weight upon an hypothesis which is ancient indeed, and hath been very generally received by philosophers, but of which I could find no solid proof. The hypothesis I mean is, That nothing is perceived but what is in the mind which perceives it: That we do not really perceive things that are X DEDICATION.
external, but only certain images and pictures of them imprinted upon the mind, which are called impressions and ideas.
If this be true; supposing certain impressions and ideas to exist in my mind, I cannot, from their existence, infer the existence of any thing else: my impressions and ideas are the only existences of which I can have any knowledge or conception; and they are such fleet- ing and transitory beings that they can have no ex- istence at all, any longer than I am conscious of them. So that, upon this hypothesis, the whole universe about me, bodies and spirits, sun, moon, stars, and earth, friends and relations, all things without exception, which I imagined to have a permanent existence, whe- ther I thought of them or not, vanish at once; And, like the baseless fabric of a vision, Leave not a track behind.
I thought it unreasonable, my Lord, upon the autho- rity of philosophers, to admit an hypothesis which, in my opinion, overturns all philosophy, all religion and virtue, and all common sense: and finding that all the systems concerning the human understanding which I •was acquainted with, were built upon this hypothesis, I resolved to inquire into this subject anew, without regard to any hypothesis.
What I now humbly present to your Lordship is the fruit of this inquiry, so far only as it regards the Five Senses; in which I claim no other merit than DEDICATION. XI that of having given great attention to the operations of my own mind, and of having expressed, with all the perspicuity I was able, what I conceive every man, who gives the same attention, will feel and perceive. The productions of imagination require a genius which soars above the common rank; but the treasures of knowledge are commonly buried deep, and may be reached by those drudges who can dig with labour and patience, though they have not wings to fly. The ex- periments that were to be made in this investigation suited me, as they required no other expense but that of time and attention, which I could bestow. The leisure of an academical life, disengaged from the pur- suits of interest and ambition; the duty of my profes- sion, which obliged me to give prelections on these subjects to the youth; and an early inclination to speculations of this kind, — have enabled me, as I flatter myself, to give a more minute attention to the subject of this Inquiry, than has been given before.
My thoughts upon this subject were, a good many years ago, put together in another form, for the use of my pupils, and afterwards were submitted to the judg- ment of a private philosophical society, of which I have the honour to be a member. A great part of this Inquiry was honoured even by your Lordship's perusal. And the encouragement which you, my Lord, and others, whose friendship is my boast, and whose judg- ment I reverence, were pleased to give me, counter- balanced my timidity and diffidence, and determined me to offer it to the public.
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If it appears to your Lordship to justify the com- mon sense and reason of mankind, against the sceptical subtilties which, in this age, have endeavoured to put them out of countenance; if it appears to throw any new light upon one of the noblest parts of the divine workmanship; your Lordship's respect for the arts and sciences, and your attention to every thing which tends to the improvement of them, as well as to every thing- else that contributes to the felicity of your country, leave me no room to doubt of your favourable accep- tance of this essay, as the fruit of my industry in a pro- fession wherein I was accountable to your Lordship; and as a testimony of the great esteem and respect wherewith I have the honour to be, MY LORD, your Lordship's most obliged, and most devoted servant, THO. REID.
AN INQUIRY INTO THE HUMAN MIND.
CHAP. I. INTRODUCTION.
SECT. L The Importance of the Subject, and the Means of Prosecuting it.
THE fabric of the human Mind is curious and wonderful, as well as that of the human body. The faculties of the one are with no less wisdom adapted to their several ends than the organs of the other. Nay it is reasonable to think, that as the mind is a nobler work, and of a higher order than the body, even more of the wisdom and skill of the Divine Architect hath been employed in its structure. It is therefore a subject highly worthy of inquiry on its own account, but still more worthy on account of the ex- tensive influence which the knowledge of it hath over every other branch of science.
In the arts and sciences which have least connexion with the mind, its faculties are the engines which we must employ; and the better we understand their nature and use, their defects and disorders, the more skilfully we shall B 2 OF THE HUMAN MIND. [CHAP. I.
apply them, and with the greater success. But in the noblest arts, the mind is also the subject upon which we operate. The painter, the poet, the actor, the orator, the moralist, and the statesman attempt to operate upon the mind in different ways and for different ends; and they succeed according as they touch properly the strings of the human frame. Nor can their several arts ever stand on a solid foundation, or rise to the dignity of science, until they are built on the principles of the human consti- tution.
Wise men now agree, or ought to agree in this, that there is but one way to the knowledge of Nature's works; the way of observation and experiment. By our consti- tution, we have a strong propensity to trace particular facts and observations to general rules, and to apply such general rules to account for other effects, or to direct us in the production of them. This procedure of the understanding- is familiar to every human creature in the common affairs of life, and it is the only one by which any real discovery in philosophy can be made.
The man who first discovered that cold freezes water, and that heat turns it into vapour, proceeded on the same general principles, and in the same method, by which Newton discovered the law of gravitation and the pro- perties of light. His regulce philosophandi are maxims of common sense, and are practised every day in common life; and he who philosophizes by other rules, either con- cerning the material system or concerning the mind, mis- takes his aim.
Conjectures and theories are the creatures of men, and will always be found very unlike the creatures of God. If we would know the works of God, we must consult themselves with attention and humility, without daring to add any thing of ours to what they declare. A just in- terpretation of nature is the only sound and orthodox phi- losophy: whatever we add of our own is apocryphal and of no authority.
All our curious theories of the formation of the earth, of the generation of animals, of the origin of natural and SECT. I.] INTRODUCTION. 3 moral evil, so far as they go beyond a just induction from facts, are vanity and folly, no less than the vortices of Des Cartes, or the Archaeus of Paracelsus. Perhaps the philosophy of the mind hath been no less adulterated by theories than that of the material system. The theory of ideas is indeed very ancient, and hath been very uni- versally received; but as neither of these titles can give it authenticity, they ought not to screen it from a free and candid examination; especially in this age, when it hath produced a system of scepticism, that seems to triumph over all science, and even over the dictates of common sense.
Ail that we know of the body is owing to anatomical dissection and observation, and it must be by an anatomy of the mind that we can discover its powers and principles.
SECT. II.
The Impediments to our Knowledge of the Mind.
BUT it must be acknowledged, that this kind of anatomy is much more difficult than the other; and therefore it needs not seem strange, that mankind have made less progress in it. To attend accurately to the operations of our minds, and make them an object of thought, is no easy matter, even to the contemplative, and to the bulk of man- kind is next to impossible.
An anatomist who hath happy opportunities, may have access to examine with his own eyes, and with equal accuracy, bodies of all different ages, sexes, and condi- tions; so that what is defective, obscure, or preternatural in one "may be discerned clearly, and in its most perfect state, in another. But the anatomist of the mind cannot have the same advantage. It is his own mind only that he can examine with any degree of accuracy and distinct- ness. This is the only subject he can look into. He may, from outward signs, collect the operations of other minds; but these signs are for the most part ambiguous, B2 4 OF THE HUMAN MIND. [CHAP. I, and must be interpreted by what he perceives within himself.
So that if a philosopher could delineate to us, distinctly and methodically, all the operations of the thinking prin- ciple within him, which no man was ever able to do, this would be only the anatomy of one particular subject; which would be both deficient and erroneous, if applied to human nature in general. For, a little reflection may satisfy us, that the difference of minds is greater than that of any other beings which we consider as of the same species.
Of the various powers and faculties we possess, there are some which nature seems both to have planted and reared, so as to have left nothing to human industry. Such are the powers which we have in common with the brutes, and which are necessary to the preservation of the individual or the continuance of the kind. There are other powers, of which nature hath only planted the seeds in our minds, but hath left the rearing of them to human culture. It is by the proper culture of these that we are capable of all those improvements in intellectuals, in taste, and in morals, which exalt and dignify human nature; while, on the other hand, the neglect or perversion of them makes it degeneracy and corruption.
The two-legged animal that eats of nature's dainties what his taste or appetite craves, and satisfies his thirst at the crystal fountain, who propagates his kind as occasion and lust prompt, repels injuries, and takes alternate labour and repose, is, like a tree in the forest, purely of nature's growth. But this same savage hath within him the seeds of the logician, the man of taste and breeding, the orator, the statesman, the man of virtue, and the saint; which seeds, though planted in his mind by nature, yet, through want of culture and exercise, must lie for ever buried, and be hardly perceivable by himself or by others.
The lowest degree of social life will bring to light some of those principles which lay hid in the savage state: and according to his training, and company, and manner of life, some of them, either by their native vigour or by the force SECT. II.] INTRODUCTION. 5 of culture, will thrive and grow up to great perfection; others will be strangely perverted from their natural form; and others checked, or perhaps quite eradicated.
This makes human nature so various and multiform in the individuals that partake of it, that, in point of morals and intellectual endowments, it fills up all that gap which we conceive to be between brutes and devils below and the celestial orders above; and such a prodigious diversity of minds must make it extremely difficult to discover the common principles of the species.
The language of philosophers, with regard to the original faculties of the mind, is so adapted to the prevailing sys- tem that it cannot fit any other; like a coat that fits the man for whom it was made, and shows him to advantage, which yet will sit very awkward upon one of a different make, although perhaps as handsome and as well propor- tioned. It is hardly possible to make any innovation in our philosophy concerning the mind and its operations, without using new words and phrases, or giving a different meaning to those that are received; a liberty which, even when necessary, creates prejudice and misconstruction, and which must wait the sanction of time to authorize it. For, innovations in language, like those in religion and government, are always suspected and disliked by the many, till use hath made them familiar and prescription have given them a title.
If the original perceptions and motions of the mind were to make their appearance single and unmixed, as we first received them from the hand of nature, one accus- tomed to reflection would have less difficulty in tracing them; but before we are capable of reflection, they are so mixed, compounded, and decompounded by habits, asso- ciations, and abstractions, that it is hard to know what they were originally. The mind may in this respect be compared to an apothecary or a chemist, whose materials indeed are furnished by nature; but for the purposes of his art, he mixes, compounds, dissolves, evaporates, and sublimes them, till they put on a quite different appear- ance; so that it is very difficult to know what they were 6 OF THE HUMAN MIND. [CHAP. I.
at first, and much more to bring them back to their original and natural form. And this work of the mind is not carried on by deliberate acts of mature reason, which we might recollect, but by means of instincts, habits, associa- tions, and other principles, which operate before we come to the use of reason; so that it is extremely difficult for the mind to return upon its own footsteps, and trace back those operations which have employed it since it first began to think and to act.
Could we obtain a distinct and full history of all that hath passed in the mind of a child, from the beginning of life and sensation, till it grows up to the use of reason; how its infant faculties began to work, and how they brought forth and ripened all the various notions, opinions, and sentiments which we find in ourselves when we come to be capable of reflection; this would be a treasure of natural history, which would probably give more light into the human faculties than all the systems of philosophers about them since the beginning of the world. But it is in vain to wish for what nature has not put within the reach of our power. Reflection, the only instrument by which we can discern the powers of the mind, comes too late to observe the progress of nature, in raising them from their infancy to perfection.
It must, therefore, require great caution and great ap- plication of mind, for a man that is grown up in all the prejudices of education, fashion, and philosophy, to un- ravel his notions and opinions, till he finds out the simple and original principles of his constitution, of which no account can be given but the will of our maker. This may be truly called an analysis of the human faculties; and till this is performed, it is in vain we expect any just system of the mind; that is, an enumeration of the original powers and laws of our constitution, and an explication from them of the various phenomena of human nature.
Success, in an inquiry of this kind, it is not in human power to command; but perhaps it is possible, by caution and humility, to avoid error and delusion. The labyrinth may be too intricate, and the thread too fine, to be traced SECT. II.] INTRODUCTION. 7 through all its windings; but jf we stop where we can trace it no further, and secure the ground we have gained, there is no harm done; a quicker eye may in time trace it further.
It is genius, and not the want of it, that adulterates philosophy, and tills it with error and false theory. A creative imagination disdains the mean offices of digging for a foundation, of removing rubbish, and carrying mate- rials: leaving these servile employments to the drudges in science, it plans a design and raises a fabric. Invention supplies materials where they are wanting, and fancy adds colouring and every befitting ornament. The work pleases the eye, and wants nothing but solidity and a good foundation. It seems even to vie with the works of nature; till some succeeding architect blows it into rub- bish, and builds as goodly a fabric of his own in its place. Happily for the present age, the castle-builders employ themselves more in romance than in philosophy. That is undoubtedly their province, and in those regions the off- spring of fancy is legitimate; but in philosophy it is all spurious.
SECT. III.
The present State of this Part of Philosophy. — Of Des Cartes, Malebranche, and Locke.
THAT our philosophy concerning the mind and its facul- ties is but in a very low state, may be reasonably conjec- tured, even by those who never have narrowly examined it. Are there any principles, with regard to the mind, settled with that perspicuity and evidence which attends the principles of mechanics, astronomy, and optics? — These are really sciences built upon laws of nature which universally obtain. What is discovered in them is no longer matter of dispute: future ages may add to it, but, till the course of nature be changed, what is already established can never be overturned". But when we turn our attention inward, and consider the phenomena of 8 OF THE HUMAN MIND. [CHAP. I.
human thoughts, opinions, and perceptions, and endeavour to trace them to the general laws and the first principles of our constitution, we are immediately involved in dark- ness and perplexity. — And if common sense or the prin- ciples of education happen not to be stubborn, it is odds but we end in absolute scepticism.
Des Cartes finding nothing established in this part of philosophy, in order to lay the foundation of it deep, resolved not to believe his own existence till he should be able to give a good reason for it. He was, perhaps, the first that took up such a resolution: but if he could in- deed have effected his purpose, and really become diffi- dent of his existence, his case would have been deplorable, and without any remedy from reason or philosophy. A man that disbelieves his own existence is surely as unfit to be reasoned with as a man that believes he is made of glass. There may be disorders in the human frame that may produce such extravagancies; but they will never be cured by reasoning. Des Cartes indeed would make us believe, that he got out of this delirium by this logical argument, Cogito, ergo sum. But it is evident he was in his senses all the time, and never seriously doubted his existence. For he takes it for granted in this argument, and proves nothing at all. I am thinking, says he, there- fore I am: and is it not as good reasoning to say, I am sleeping, therefore I am? or, I am doing nothing, there- fore I am? If a body moves it must exist no doubt; but if it is at rest, it must exist likewise.
Perhaps Des Cartes meant not to assume his own existence in this enthymeme, but the existence of thought; and to infer from that the existence of a mind or subject of thought. But why did he not prove the existence of his thought? Consciousness, it may be said, vouches that. But who is voucher of consciousness? Can any man prove that his consciousness may not deceive him? No man can: nor can we give a better reason for trusting to it than that every man, while his mind is sound, is determined by the constitution of his nature, to give im- plicit belief to it, and to laugh at or to pity the man who SECT. III.] INTRODUCTION. 9 doubts its testimony. And is not every man in his wits, as much determined to take his existence upon trust as his consciousness?
The other proposition assumed in this argument, That thought cannot be without a mind or subject, is liable to the same objection: not that it wants evidence; but that its evidence is no clearer nor more immediate than that of the proposition to be proved by it. And taking all these propositions together, — I think, — I am conscious, — Every thing that thinks exists, — I exist, — would not every sober man form the same opinion of the man who seri- ously doubted any one of them? And if he was his friend, would he not hope for his cure from physic and good regimen, rather than from metaphysic and logic?
But supposing it proved, that my thought and my con- sciousness must have a subject, and consequently that I exist, how do I know that all that train and succession of thought which I remember belong to one subject, and that the I of this moment is the very individual I of yes- terday and of times past?
Des Cartes did not think proper to start this doubt: but Locke has done it; and, in order to resolve it, gravely determines that personal identity consists in conscious- ness; that is, if you are conscious that you did such a thing a twelvemonth ago, this consciousness makes you to be the very person that did it. Now, consciousness of what is past can signify nothing else but a remembrance that I did it. So that Locke's principle must be, That identity consists in remembrance; and consequently a man must lose his personal identity with regard to every thing he forgets.
Nor are these the only instances whereby our philoso- phy concerning the mind appears to be very fruitful in cre- ating doubts, but very unhappy in resolving them.
Des Cartes, Malebranche, and Locke have all em- ployed their genius and skill to prove the existence of a material world; and with very bad success. Poor un- taught mortals believe, undoubtedly, that there is a sun, moon, and stars; an earth, which we inhabit; country, B3 10 OF THE HUMAN MIND. [CHAP. I.