Thomas Reid

An Inquiry into the Human Mind: On the Principles of Common Sense

Published by Good Press, 2021
EAN 4064066316310

Table of Contents


Thomas Reid, An Inquiry into the Human Mind: on the Principles of Common Sense (1764). From Reid’s Works (Charleston: Etheridge, 1813), Vol 1. Footnotes not included.



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 extensive influence which the knowledge of it hath over every other branch of science.

In the arts and sciences which have least connection 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 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 constitution.

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 constitution, 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 properties of light. His reguloo philosophandi are maxims of common sense, and are practised every day in common life; and he who philosophizes by other rules, either concerning the material system, or concerning the mind, mistakes 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 interpretation of nature is the only sound and orthodox philosophy: 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 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 ArchTus of Paracelsus. Perhaps the philosophy of the mind has been no less adulterated by theories than that of the material system. The theory of ideas is indeed very ancient, and hath been very universally 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 skepticism, that seems to triumph over all science, and even over the dictates of common sense.

All that we know of the body, is owing to anatomical dissection and observation, and it must be by anatomy of the mind that we can discover its powers and principles.


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 operation of our minds, and make them an object of thought, is no easy matter even to the contemplative, and to the bulk of mankind 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 conditions; 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 distinctness. 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, 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 principle 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 its 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 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 system, 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 set very awkward upon one of a different make, although perhaps as handsome and as well proportioned. 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 has made them familiar, and prescription hath given them a title.

If the original perceptions and notions of the mind were to make their appearance single and unmixed, as we first received them from the hand of nature, one accustomed to reflection would have less difficulty in tracing them; but before we are capable of reflection, they are so mixe , compounded and decompounded, by habits, associations 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 chymist, 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 appearance; so that it is very difficult to know what thev were 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, associations, 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 application of mind, for a man that is grown up in all the prejudices of education, fashion, and philosophy, to unravel 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 through all its windings; but if 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 fills it with error and false theory. A creative imagination disdains the mean offices of digging for a foundation, of removing rubbish, and carrying materials: 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 rubbish, 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 offspring of fancy is legitimate; but in philosophy it is all spurious.


That our philosophy concerning the mind and its faculties, is but in a very low state, may be reasonably conjectured, 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 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 darkness and perplexity. And if common sense, or the principles of education, happen not to be stubborn, it is odds but we end in absolute skepticism.

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 indeed have effected his purpose, and really become diffident 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 wai in his senses all the time, and never seriously doubted of his existence. For he takes it for granted in this argument, and proves nothing at all. I am thinking, says he, therefore I am: and is it not as good reasoning to say, I am sleeping, therefore I am? or, I am doing nothing, therefore 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 for 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 everv man, while his mind is sound, is determined, by the constitution of his nature, to give implicit belief to it, and to laugh at, or pity, the man who 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 seriously 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 consciousness must have a subject, and consequently that I exist, how do I know that all that train and succession of thoughts which I remember belong to one subject, and that the I of this moment, is the very individual I of yesterday, and of times past?

Des Cartes did not think it proper to start this doubt: but Locke has done it; and, in order to resolve it, gravely determines, that personal identity consists in consciousness; 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 the 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 philosophy concerning the mind appears to be very fruitful in creating doubts, but very unhappy in resolving them.

Des Cartes, Malebranche, and Locke, have all employed their genius and skill, to prove the existence of a material world; and with very bad success. Poor untaught mortals believe undoubtedly, that there is a sun, moon, and stars; an earth, which we inhabit; country, friends, and relations, which we enjoy; land, houses and moveables, which we possess. But philosophers, pitying the credulity of the vulgar, resolve to have no faith but what is founded upon reason. They apply to philosophy to furnish them with reasons for the belief of those things, which all mankind have believed without being able to give any reason for it. And surely one would expect, that, in matters of such importance, the proof would not be difficult: but it is the most difficult thing in the world. For these three great men, with the best good will, have not been able, from all the treasures of philosophy, to draw one argument, that is fit to convince a man that can reason, of the existence of any one thing without him. Admired Philosophy! daughter of light! parent of wisdom and knowledge! if thou art she! surely thou hast not yet arisen upon the human mind, nor blessed us with more of thy rays, than are sufficient to shed a "darkness visible" upon the human faculties, and to disturb that repose and security which happier mortals enjoy, who never approached thine altar, nor felt thine influence! But if indeed thou hast not power to dispel those clouds and phantoms which thou hast discovered or created, withdraw this penurious and malignant ray: I despise philosophy, and renounce its guidance; let my soul dwell with common sense.


But instead of despising the dawn of light, we ought rather to hope for its increase: instead of blaming the philosophers I have mentioned, for the defects and blemishes of their system, we ought rather to honour their memories, as the first discoverers of a region in philosophy formerly unknown; and, however lame and imperfect the system may be, they have opened the way to future discoveries, and are justly entitled to a great share in the merit of them. They have removed an infinite deal of dust and rubbish, collected in the ages of scholastic sophistry, which had obstructed the way. They have put us in the right road, that of experience and accurate reflection. They have taught us to avoid the snares of ambiguous and ill-defined words, and have spoken and thought upon this subject with a distinctness and perspicuity formerly unknown. They made many openings that may lead to the discovery of truths which they did not reach, or to the detection of errors in which they were involuntarily entangled.

It may be observed, that the defects and blemishes in the received philosophy concerning the mind, which have most exposed it to the contempt and ridicule of sensible men, have chiefly been owing to this; that the votaries of this philosophy, from a natural prejudice in her favour, have endeavoured to extend her jurisdiction beyond its just limits, and to call to her bar the dictates of common sense. But these decline this jurisdiction; they disdain the trial of reasoning, and disown its authority; they neither claim its aid, nor dread its attacks.

In this unequal contest betwixt common sense and philosophy, the latter will always come off both with dishonour and loss; nor can she ever thrive till this rivalship is dropped, these encroachments given up, and a cordial friendship restored: for, in reality, common sense holds nothing of philosophy, nor needs her aid. But, on the other hand, philosophy, if I may be permitted to change the metaphor, has no other root but the principles of common sense; it grows out of them, and draws its nourishment from them: severed from this root, its honours wither, its sap is dried up, it dies and rots.

The philosophers of the last age whom I have mentioned, did not attend to the preserving this union and subordination so carefully as the honour and interest of philosophy required: but those of the present have waged open war with common sense, and hope to make a complete conquest of it by the subtilties of philosophy; an attempt no less audacious and vain, than that of the giants to dethrone almighty Jove.


The present age, I apprehend, has not produced two more acute or more practised in this part of philosophy than the Bishop of Cloyne, and the author of the Treatise of Human Nature. The first was no friend to skepticism, but had that warm concern for religious and moral principles which became his order: yet the result of his inquiry was a serious conviction, that there is no such thing as a material world nothing in nature but spirits and ideas: and that the belief of material substances, and of abstract ideas, are the chief causes of all our errors in philosophy, and of all infidelity and heresy in religion. His arguments are founded upon the principles which were formerly laid down by Des Cartes, Malebranche, and Locke, and which have been very generally received.

And the opinion of the ablest judges seems to be, that they neither have been, nor can be confuted; and that he hath proved, by unanswerable arguments, what no man in his senses can believe.

The second proceeds upon the same principles, but carries them to their full length; and as the Bishop undid the whole material world, this author upon the same grounds, undoes the world of spirits, and leaves nothing in nature but ideas and impressions, without any subject on which they may be impressed.

It seems to be a peculiar strain of humour in this author, to set out in his introduction, by promising with a grave face, no less than a complete system of the sciences, upon a foundation entirely new, to wit, that of human nature; when the intention of the whole work is to shew, that there is neither human nature nor science in the world. It may perhaps be unreasonable to complain of this conduct in an author, who neither believes his own existence, nor that of his reader; and therefore could not mean to disappoint him, or to laugh at his credulity. Yet I cannot imagine, that the author of the Treatise of Human Nature is so skeptical as to plead this apology. He believed, against his principles, that he should be read, and that he should retain his personal identity, till he reaped the honour and reputation justly due to his metaphysical acumen. Indeed he ingenuously acknowledges, that it was only in solitude and retirement that he could yield any assent to his own philosophy; society, like daylight, dispelled the darkness and fogs of skepticism, and made him yield to the dominion of common sense. Nor did I ever hear him charged with doing any thing, even in solitude, that argued such a degree of skepticism, as his principles maintain. Surely if his friends apprehended this, they would have the charity never to leave him alone.

Pyrrho the Elean, the father of this philosophy, seems to have carried it to greater perfection than any of his successors; for if we may believe Antigonus the Carystian, quoted by Diogenes Laertius, his life corresponded to his doctrine. And therefore, if a cart run against him, or a dog attacked him, or if he came upon a precipice, he would not stir a foot to avoid the danger, giving no credit to his senses. But his attendants, who, happily for him, were not so great skeptics, took care to keep him out of harm's way; so that he lived till he was ninety years of age. Nor is it to be doubted, but this author's friends would have been equally careful to keep him from harm, if ever his principles had taken too strong a hold of him.

It is probable the Treatise of Human Nature was not written in company; yet it contains manifest indications, that the author every now and then relapsed into the faith of the vulgar, and could hardly, for half a dozen pages, keep up the skeptical character.

In like manner, the great Pyrrho himself forgot his principles on some occasions; and is said once to have been in such a passion with his cook, who probably had not roasted his dinner to his mind, that with the spit in his hand, and the meat upon it, he pursued him even into the market-place.

It is a bold philosophy that rejects, without ceremony, principles which irresistibly govern the belief and the conduct of all mankind in the common concerns of life; and to which the philosopher himself must yield, after he imagines he hath confuted them. Such principles are older, and of more authority, than philosophy: she rests upon them as her basis, not they upon her. If she could overturn them, she must be buried in their ruins- but all the engines of philosophical subtilty are too weak for this purpose; and the attempt is no less ridiculous, than if a mechanic should contrive an axis in peritrochio to remove the earth out of its place; or if a mathematician should pretend to demonstrate, that things equal to the same thing, are not equal to one another.

Zeno endeavoured to demonstrate the impossibility of motion; Hobbes, that there was no difference between right and wrong; and this author, that no credit is to be given to our senses, to our memory, or even to demonstration. Such philosophy is justly ridiculous, even to those who cannot detect the fallacy of it. It can have no other tendency, than to shew the acuteness of the sophist, at the expense of disgracing reason and human nature, and making mankind Yahoos.


There are other prejudices against this system of human nature, which, even upon a general view, may make one diffident of it. Des Cartes, Hobbes, and this author, have each of them given us a system of human nature; an undertaking too vast for any one man, how great soever his genius and abilities may be. There must surely be reason to apprehend, that many parts of human nature never came under their observation; and that others have been stretched and distorted, to fill up blanks, and complete the system. Christopher Columbus, or Sebastian Cabot might almost as reasonably have undertaken to give us a complete map of America.

There is a certain character and style in nature's works, which is never attained in the most perfect imitation of them. This seems to be wanting in the systems of human nature I have mentioned, and particularly in the last. One may see a puppet make a variety of motions and gesticulations, which strike much at first view; but when it is accurately observed, and taken to pieces, our admiration ceases; we comprehend the whole art of the maker. How unlike is it to that which it represents; what a poor piece of work compared with the body of a man, whose structure the more we know, the more wonders we discover in it, and the more sensible we are of our ignorance! Ts the mechanism of the mind so easily comprehended, when that of the body is so difficult? Yet by this system, three laws of association, joined to a few original feelings, explain the whole mechanism of sense, imagination, memory, belief, and of all the actions and passions of the mind. Is this the man that nature made? I suspect it is not so easy to look behind the scenes in nature's work. This is a puppet surely, contrived by too bold an apprentice of nature, to mimic her work. It shews tolerably by candle light, but brought into clear day, and taken to pieces, it will appear to be a man made with mortar and a trowel. The more we know of other parts of nature, the more we like and approve them. The little I know of the planetary system; of the earth which we inhabit; of minerals, vegetables, and animals; of my own body, and of the laws which obtain in these parts of nature; opens to my mind grand and beautiful scenes, and contributes equally to my happiness and power. But when I look within, and consider the mind itself which makes me capable of all these prospects and enjoyments; if it is indeed what the Treatise of Human Nature makes it, I find I have been only in an enchanted castle, imposed upon by spectres and apparitions. I blush inwardly to think how I have been deluded; I am ashamed of my frame, and can hardly forbear expostulating with my destiny: Is this thy pastime, 0 Nature, to put such tricks upon a silly creature, and then to take off the mask, and shew him how he hath been befooled? If this is the philosophy of human nature, my soul enter thou not into her secrets. It is surely the forbidden tree of knowledge; I no sooner taste of it, than I perceive myself naked, and stripped of all things, yea, even of my very self. I see myself, and the whole frame of nature, shrink into fleeting ideas, which, like Epicurus's atoms, dance about in emptiness.


But what if these profound disquisitions into the first principles of human nature, do naturally and necessarily plunge a man into this abyss of skepticism? May we not reasonably judge so from what hath happened? Des Cartes no sooner began to dig in this mine, than skepticism was ready to break in upon him. He did what he could to shut it out. Malebranche and Locke, who dug deeper, found the difficulty of keeping out this enemy still to increase; but they laboured honestly in the design. Then Berkeley, who carried on the work, despairing of securing all, bethought himself of an expedient: by giving up the material world, which he thought might be spared without loss, and even with advantage, he hoped, by an impregnable partition, to secure the world of spirits. But, alas! the Treatise of Human Nature wantonly sapped the foundation of this partition, and drowned all in one universal deluge.

These facts, which are undeniable, do indeed give reason to apprehend, that Des Cartes's system of the human understanding, which I shall beg leave to call the ideal system, and which, with some improvements made by later writers, is now Generally received, hath some original defect; that this skepticism is inlaid in it, and reared along with it; and, therefore, that we must lay it open to the foundation, and examine the materials, before we can expect to raise any solid and useful fabric of knowledge on this subject.


But is this to be despaired of, because Des Cartes and his followers have failed? By no means. This pusillanimity would be injurious to ourselves, and injurious to truth. Useful discoveries are sometimes indeed the effect of superior genius, but more frequently they are the birth of time and of accidents. A traveller of good judgment may mistake his way, and be unawares led into a wrong track; and while the road is fair before him, he may go on without suspicion and be followed by others; but when it ends in a coal-pit, it requires no great judgment to know that he hath gone wrong, nor perhaps to find out what had misled him.

In the mean time, the unprosperous state of this part of philosophy hath produced an effect, somewhat discouraging indeed to any attempt of this nature, but an effect which might be expected, and which time only and better success can remedy. Sensible men, who never will be skeptics in matters of common life, are apt to treat with sovereign contempt every thing that hath been said, or is to be said, upon this subject. It is metaphysics say they: who minds it? Let scholastic sophisters entangle themselves in their own cobwebs: I am resolved to take my own existence, and the existence of other things, upon trust; and to believe that snow is cold, and honey sweet, whatever they may say to the contrary. He must either be a fool, or want to make a fool of me, that would reason me out of my reason and senses.

I confess I know not what a skeptic can answer to this, nor by what good argument he can plead even for a hearing; for either his reasoning is sophistry, and so deserves contempt; or there is no truth in the human faculties, and then why should we reason?

If therefore a man find himself entangled in these metaphysical toils, and can find no other way to escape, let him bravely cut the knot which he cannot loose, curse metaphysics and dissuade every man from meddling with it. For if I have been led into bogs and quagmires by following an ignis fatuus, what can I do better, than to warn others to beware of it? If philosophy contradicts herself, befools her votaries, and deprives them of every object worthy to be pursued or enjoyed, let her be sent back to the infernal regions from which she must have had her original.

But is it absolutely certain that this fair lady is of the party? Is it not possible she may have been misrepresented? Have not men of genius in former ages often made their own dreams to pass for her oracles? Ought she then to be condemned without any further hearing? This would be unreasonable. I have found her in all other matters an agreeable companion, a faithful counsellor, a friend to common sense, and to the happiness of mankind. This justly entitles her to my correspondence and confidence, till I find infallible proofs of her infidelity.



It is so difficult to unravel the operations of the human understanding, and to reduce them to their first principles, that we cannot expect to succeed in the attempt, but by beginning with the simplest and proceeding by very cautious steps to the more complex. The five external senses may, for this reason, claim to be first considered in an analysis of the human faculties. And the same reason ought to determine us to make a choice even among the senses, and to give the precedence, not to the noblest, or most useful, but to the simplest, and that whose objects are least in danger of being mistaken for other things.

In this view an analysis of our sensations may be carried on, perhaps with most ease and distinctness, by taking them in this order: smelling, tasting, hearing, touch, and, last of all, seeing.

Natural philosophy informs us, that all animal and vegetable bodies, and probablv all or most other bodies, while exposed to the air, are continually sending forth effluvia of vast subtilty, not only in their state of life and growth, but in the states of fermentation and putrefaction. These volatile particles do probably repel each other, and so scatter themselves in the air, until they meet with other bodies to which they have some chymical affinity, and with which they unite and form new concretes. All the smell of plants, and of other bodies, is caused by these volatile parts, and is smelled wherever they are scattered in the air; and the acuteness of smell in some animals, shews us, that these effluvia spread far, and must be inconceivably subtile.

Whether, as some chymists conceive, every species of bodies hath a spiritus rector, a kind of soul, which causes the smell, and all the specific virtues of that body, and which, being extremely volatile, flies about in the air in quest of a proper receptacle, I do not inquire. This, like most other theories, is perhaps rather the product of imagination than of just induction. But that all bodies are smelled by means of effluvia which they emit and which are drawn into the nostrils along with the air, there is no reason to doubt. So that there is manifest appearance of design in placing the organ of smell in the inside of that canal, through which the air is continually passing in inspiration and expiration.

Anatomy informs us, that the membrane pituitaria, and the olfactory nerves, which are distributed to the villous parts of this membrane, are the organs destined by the wisdom of nature to this sense; so that when a body emits no effluvia, or when they do not enter into the nose, or when the pituitary membrane or olfactory nerves are rendered unfit to perform their office, it cannot be smelled.

Yet notwithstanding this, it is evident that neither the organ of smell, nor the medium, nor any motions we can conceive excited in the membrane above mentioned, or in the nerve or animal spirits, do in the least resemble the sensation of smelling; nor could that sensation of itself ever have led us to think of nerves, animal spirits, and effluvia.


Having premised these things, with regard to the medium and organ of this sense, let us now attend carefully to what the mind is conscious of when we smell a rose or a lily; and since our language affords no other name for this sensation, we shall call it a smell or odour, carefully excluding from the meaning of those names every thing but the sensation itself, at least till we have examined it.

Suppose a person who never had this sense before, to receive it all at once, and to smell a rose; can he perceive any similitude or agreement between the smell and the rose? or indeed between it and any other object whatsoever? Certainly he cannot. He finds himself affected in a new way, he knows not why or from what cause. Like a man that feels some pain or pleasure formerly unknown to him, he is conscious that he is not the cause of it himself; but cannot, from the nature of the thing, determine whether it is caused by body or spirit, by something near, or by something at a distance. It has no similitude to any thing else, so as to admit of a comparison; and therefore he can conclude nothing from it, unless perhaps that there must be some unknown cause of it.

It is evidently ridiculous, to ascribe to it figure, colour, extension, or any other quality of bodies. He cannot give it a place, any more than he can give a place to melancholy or joy: nor can he conceive it to have any existence, but when it is smelled. So that it appears to be a simple and original affection or feeling of the mind, altogether inexplicable and unaccountable. It is indeed impossible that it can be in any body: it is a sensation; and a sensation can only be in a sentient thing.

The various odours have each their diffierent degrees of strength or weakness. Most of them are agreeable or disagreeable; and frequently those that are agreeable when weak are disagreeable when stronger. When we compare different smells together, we can perceive very few resemblances or contrarieties, or indeed relations of any kind between them. They are all so simple in themselves, and so different from each other, that it is hardly possible to divide them into genera and species. Most of the names we give them are particular; as the smell of a rose, of a jasmine, and the like. Yet there are some general names; as sweet, stinking, musty, putrid, cadaverous, aromatic. Some of them seem to refresh and animate the mind, others to deaden and depress it.


So far we have considered this sensation abstractly. Let us next compare it with other things to which it bears some relation. And first I shall compare this sensation with the remembrance, and the imagination of it.

I can think of the smell of a rose when I do not smell it; and it is possible that when I think of it, there is neither rose nor smell any where existing. But when I smell it, I am necessarily determined to believe that the sensation really exists. This is common to all sensations, that as they cannot exist but in being perceived, so they cannot be perceived but they must exist. I could as easily doubt of my own existence, as of the existence of my sensations. Even those profound philosophers who have endeavoured to disprove their own existence, have yet left their sensations to stand upon their own bottom, stripped of a subject, rather than call in question the reality of their existence.

Here then a sensation, a smell for instance, may be presented to the mind three different ways: it may be smelled, it may be remembered, it may be imagined or thought of. In the first case, it is necessarily accompanied with a belief of its present existence; in the second, it is necessarily accompanied with a belief of its past existence; and in the last, it is not accompanied with belief at all, but is what the logicians call a simple apprehension.

Why sensation should compel our belief of the present existence of the thing, memory a belief of its past existence, and imagination no belief at all, I believe no philosopher can give a shadow of reason, but that such is the nature of these operations. They are all simple and original, and therefore inexplicable acts of the mind.

Suppose that once, and only once, I smelled a tuberose in a certain room where it grew in a pot, and gave a very grateful perfume. Next day I relate what I saw and smelled. When I attend as carefully as I can to what passes in my mind in this case, it appears evident, that the very thing I saw yesterday, and the fragrance I smelled, are now the immediate objects of my mind when I remember it. Further, I can imagine this pot and flower transported to the room where I now sit, and yielding the same perfume. Here likewise it appears, that the individual thing which I saw and smelled, is the object of my imagination.

Philosophers indeed tell me, that the immediate object of my memory and imagination in this case, is not the past sensation, but an idea of it, an image, phantasm, or species of the odour I smelled: that this idea now exists in my mind, or in my sensorium; and the mind contemplating this pleasant idea, finds it a representation of what is past, or of what may exist; and accordingly calls it memory, or imagination. This is the doctrine of the ideal philosophy; which we shall not now examine, that we may not interrupt the thread of the present investigation. Upon the strictest attention, memory appears to me to have things that are past, and not present ideas for its object. We shall afterward examine this system of ideas, and endeavour to make it appear, that no solid proof has ever been advanced of the existence of ideas; that they are a mere fiction and hypothesis contrived to solve the phenomena of the human understanding; that they do not at all answer this end; and that this hypothesis of ideas or images of things in the mind, or in the sensorium, is the parent of those many paradoxes so shocking to common sense, and of that skepticism, which disgrace our philosophy of the mind, and have brought upon it the ridicule and contempt of sensible men.

In the mean time, I beg leave to think with the vulgar, that when I remember the smell of the tuberose, that very sensation which I had yesterday, and which has now no more any existence, is the immediate object of my memory; and when I imagine it present, the sensation itself, and not any idea of it, is the object of my imagination. But though the object of my sensation, memory, and imagination, be in this case the same, yet these acts or operations of the mind are as different, and as easily distinguishable, as smell, taste, and sound. I am conscious of a difference in kind between sensation and memory, and between both and imagination. I find this also, that the sensation compels my belief of the present existence of the smell, and memory my belief of its past existence. There is a smell, is the immediate testimony of sense; there was a smell, is the immediate testimony of memory. If you ask me, why I believe that the smell exists? I can give no other reason, nor shall ever be able to give any other, than that I smell it. If you ask, why I believe that it existed yesterday; I can give no other reason but that I remember it.

Sensation and memory therefore are simple, original, and perfectly distinct operations of the mind, and both of them are original principles of belief. Imagination is distinct from both, but is no principle of belief. Sensation implies the present existence of its object; memory its past existence; but imagination views its object naked, and without any belief of its existence or non-existence, and is therefore what the schools call simple apprehension.


But here again the ideal system comes in our way; it teaches us, that the first operation of the mind about its ideas, is simple apprehension; that is, the bare conception of a thing without any belief about it; and that after we have got simple apprehension, by comparing them together, we perceive agreements or disagreements between them; and that this perception of the agreement or disagreement of ideas, is all that we call belief, judgment, or knowledge. Now, this appears to me to be all fiction, without any foundation in nature: for it is acknowledged by all, that sensation must go before memory and imagination; and hence it necessarily follows, that apprehension accompanied with belief and knowledge, must go before simple apprehension, at least in the matters we are now speaking of. So that here, instead of saying, that the belief or knowledge is got by putting together and comparing the simple apprehensions, we ought rather to say, that the simple apprehension is performed by resolving and analyzing a natural and original judgment. And it is with the operations of the mind, in this case, as with natural bodies, which are indeed compounded of simple principles or elements. Nature does not exhibit these elements separate, to be compounded by us; she exhibits them mixed and compounded in concrete bodies, and it is only by art and chymical analysis that they can be separated.


But what is this belief or knowledge which accompanies sensation and memory? Every man knows what it is, but no man can define it. Does any man pretend to define sensation, or to define consciousness? It is happy indeed that no man does. And if no philosopher had attempted to define and explain belief, some paradoxes in philosophy, more incredible than ever were brought forth by the most abject superstition, or the most frantic enthusiasm, had never seen the light. Of this kind surely is that modern discovery of the ideal philosophy, that sensation, memory, belief and imagination, when they have the same object, are only different degrees of strength and vivacity in the idea. Suppose the idea to be that of a future state after death; one man believes it firmly; this means no more than that he hath a strong and lively idea of it. Another neither believes nor disbelieves; that is, he has a weak and faint idea. Suppose now a third person believes firmly that there is no such thing; I am at a loss to know whether his idea be faint or lively: if it is faint, then there may be a firm belief where the idea is faint; if the idea is lively, then the belief of a future state, and the belief of no future state must be one and the same. The same arguments that are used to prove that belief implies only a stronger idea of the object than simple apprehension, might as well be used to prove that love implies only a stronger idea of the object than indifference. And then what shall we say of hatred, which must upon this hypothesis be a degree of love, or a degree of indifference? If it should be said, that in love there is something more than an idea, to wit, an affection of the mind; may it not be said with equal reason, that in belief there is something more than an idea, to wit, an assent or persuasion of the mind.

But perhaps it may be thought as ridiculous to argue against this strange opinion, as to maintain it. Indeed, if a man should maintain, that a circle, a square, and a triangle, differ only in magnitude, and not in figure, I believe he would find no body disposed either to believe him or to argue against him; and yet I do not think it less shocking to common sense, to maintain, that sensation, memory, and imagination, differ only in degree, and not in kind. I know it is said, that in a delirium, or in dreaming, men are apt to mistake one for the other. But does it follow from this, that men who are neither dreaming, nor in a delirium, cannot distinguish them? But how does a man know that he is not in a delirium; I cannot tell: neither can I tell how a man knows that he exists. But if any man seriously doubts whether he is in a delirium, I think it highly probable that he is, and that it is time to seek for a cure, which I am persuaded he will not find in the whole system of logic.

I mentioned before Locke's notion of belief or knowledge: he holds that it consists in a perception of the agreement or disagreement of ideas; and this he values himself upon as a very important discovery.