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Principles of Human Knowledge
by George Berkeley
The original, squashed down to read in about 20 minutes

(Dublin, 1710)

George Berkeley of Trinity College Dublin was, at various times (when not engaged in 'converting the savage Americans to Christianity'), Dean, Lecturer in Greek, Hebrew and Optics. His fame rests on this espousal of 'subjective idealism'- the idea that things might well have no existence at all outside our consciousness, a concept irritatingly difficult to refute, though Dr Johnson famously kicked a stone, saying 'Sir, I refute it thus!'.
Abridged: GH

Principles of Human Knowledge

To the Right Honourable THOMAS, EARL OF PEMBROKE

My Lord,
    That a man who has written something with a design to promote Useful Knowledge and Religion in the world should make choice of your lordship for his patron, will not be thought strange by any one acquainted with the present state of the church and learning, and knowing how great an ornament and support you are to both. Thus I lay this treatise at your lordship's feet.

Your lordship's most humble and most devoted servant,


Philosophy being THE STUDY OF WISDOM AND TRUTH, it may be expected that those who have spent most time and pains in it should enjoy a greater calm and serenity of mind, and greater clearness of knowledge. Yet we see the illiterate bulk of mankind that walk the high-road of plain common sense, for the most part easy and undisturbed. But no sooner do we follow the light of a superior principle, but a thousand scruples spring up, and we are insensibly drawn into uncouth paradoxes and forlorn Scepticism.

Upon the whole, I am inclined to think that the far greater part, if not all, of those difficulties which have hitherto amused philosophers, and blocked up the way to knowledge, are entirely owing to ourselves - that we have first raised a dust and then complain we cannot see.

Unless we take care TO CLEAR THE FIRST PRINCIPLES OF KNOWLEDGE FROM THE embarras and DELUSION OF WORDS, we may make infinite reasonings upon them to no purpose; we may draw consequences from consequences, and be never the wiser.


OBJECTS OF HUMAN KNOWLEDGE. - It is evident to any one who takes a survey of the objects of human knowledge, that they are either IDEAS actually imprinted on the senses; or ideas formed by help of memory and imagination. By sight I have the ideas of light and colours. By touch I perceive hard and soft, heat and cold, motion and resistance. Smelling furnishes me with odours; the palate with tastes; and hearing conveys sounds to the mind. And as several of these are observed to accompany each other, they come to be marked by name, and so to be reputed as one thing. Thus, for example a certain colour, taste, smell, figure and consistence having been observed to go together, are accounted one distinct thing, signified by the name APPLE. Other collections of ideas constitute a stone, a tree, a book, and the like sensible things - which as they are pleasing or disagreeable excite the passions of love, hatred, joy, grief, and so forth.

MIND - SPIRIT - SOUL. - But, besides all that endless variety of ideas or objects of knowledge, there is likewise something which knows or perceives them, which I call MIND, SPIRIT, SOUL, or MYSELF.

HOW FAR THE ASSENT OF THE VULGAR CONCEDED. - That neither our thoughts, nor passions, nor ideas formed by the imagination, exist WITHOUT the mind, is what EVERYBODY WILL ALLOW. Their ESSE is PERCIPI, nor is it possible they should have any existence out of the minds or thinking things which perceive them.

Some truths are so obvious to the mind that a man need only open his eyes to see them. Such I take this important one to be, viz., that all the choir of heaven and furniture of the earth, in a word all those bodies which compose the mighty frame of the world, have not any subsistence without a mind; that consequently so long as they are not actually perceived by me, or do not exist in my mind or that of any other CREATED SPIRIT, they must either have no existence at all, OR ELSE SUBSIST IN THE MIND OF SOME ETERNAL SPIRIT.

THE PHILOSOPHICAL NOTION OF MATTER INVOLVES A CONTRADICTION. - Some make a DISTINCTION betwixt PRIMARY and SECONDARY qualities. By the former they mean extension, figure, motion, rest, solidity or impenetrability, and number; by the latter they denote all other sensible qualities, as colours, sounds, tastes, and so forth. But it is evident that extension, figure, and motion are ONLY IDEAS EXISTING IN THE MIND, and that an idea can be like nothing but another idea, and that consequently neither they nor their archetypes can exist in an UNPERCEIVING substance. Hence, it is plain that that the very notion of what is called MATTER or CORPOREAL SUBSTANCE, involves a contradiction in it.

ARGUMENT AD HOMINEM. - Again, GREAT and SMALL, SWIFT and SLOW, ARE ALLOWED TO EXIST NOWHERE WITHOUT THE MIND, being entirely RELATIVE, and changing as the frame or position of the organs of sense varies. Without the mind there is neither great nor small, the motion neither swift nor slow, that is, they are nothing at all. But, say you, there is extension in general, and motion in general. But without extension solidity cannot be conceived, the same must also be true of solidity.

That NUMBER is entirely THE CREATURE OF THE MIND, and dependent on men's understanding, that it is strange to think how any one should give it an absolute existence without the mind.

PHILOSOPHICAL MEANING OF "MATERIAL SUBSTANCE". - If we inquire into what the most accurate philosophers declare themselves to mean by MATERIAL SUBSTANCE, we shall find them acknowledge they have no other meaning annexed to those sounds but the idea of BEING IN GENERAL.

THE EXISTENCE OF EXTERNAL BODIES AFFORDS NO EXPLICATION OF THE MANNER IN WHICH OUR IDEAS ARE PROCUCED. - Though we give the materialists their external bodies, they by their own confession are never the nearer knowing how our ideas are produced. Hence it is evident the production of ideas or sensations in our minds can be no reason why we should suppose Matter or corporeal substances, SINCE THAT IS ACKNOWLEDGED TO REMAIN EQUALLY INEXPLICABLE WITH OR WITHOUT THIS SUPPOSITION.

Were it necessary to add any FURTHER PROOF AGAINST THE EXISTENCE OF MATTER after what has been said, I could instance several of those errors and difficulties (not to mention impieties) which have sprung from that tenet. It has occasioned numberless controversies and disputes in philosophy, and not a few in religion. But I shall not enter into the detail of them in this place.

CAUSE OF IDEAS. - We perceive a continual succession of ideas, some are anew excited, others are changed or totally disappear. There is therefore some cause of these ideas, whereon they depend, and which produces and changes them. That this cause cannot be any quality or idea or combination of ideas, is clear from the preceding section. I must therefore be a substance; but it has been shown that there is no corporeal or material substance: it remains therefore that the CAUSE OF IDEAS is an incorporeal active substance or Spirit.

NO IDEA OF SPIRIT. - A spirit is one simple, undivided, active being - as it perceives ideas it is called the UNDERSTANDING, and as it produces or otherwise operates about them it is called the WILL. Such is the nature of SPIRIT that it cannot be of itself perceived, BUT ONLY BY THE EFFECTS WHICH IT PRODUCETH.

LAWS OF NATURE. - The ideas of Sense are more strong, lively, and DISTINCT than those of the imagination; they have likewise a steadiness, order, and coherence, and are not excited at random, as those which are the effects of human wills often are, but in a regular train or series, the admirable connexion whereof sufficiently testifies the wisdom and benevolence of its Author. Now THE SET RULES OR ESTABLISHED METHODS WHEREIN THE MIND WE DEPEND ON EXCITES IN US THE IDEAS OF SENSE, ARE CALLED THE LAWS OF NATURE; and these we learn by experience, which teaches us that such and such ideas are attended with such and such other ideas, in the ordinary course of things.

KNOWLEDGE NECESSARY FOR THE CONDUCT OF WORLDLY AFFAIRS. - This gives us a sort of foresight which enables us to regulate our actions for the benefit of life. That food nourishes, sleep refreshes, and fire warms us; that to sow in the seed-time is the way to reap in the harvest - all this we know, NOT BY DISCOVERING ANY NECESSARY CONNEXION BETWEEN OUR IDEAS, but only by the observation of the settled laws of nature, without which we should be all in uncertainty and confusion, and a grown man no more know how to manage himself in the affairs of life than an infant just born.

OF REAL THINGS AND IDEAS OR CHIMERAS. - The ideas imprinted on the Senses by the Author of nature are called REAL THINGS. The ideas of Sense are allowed to have more reality in them, that is, to be more (1) STRONG, (2) ORDERLY, and (3) COHERENT than the creatures of the mind; but this is no argument that they exist without the mind.

FIRST GENERAL OBJECTION. - ANSWER. We must now answer any objections, and if I seem too prolix to those of quick apprehensions, I hope it may be pardoned, since all men do not equally apprehend things of this nature, and I am willing to be understood by every one.

FIRST, it will be objected that by the foregoing principles ALL THAT IS REAL AND SUBSTANTIAL IN NATURE IS BANISHED OUT OF THE WORLD. I ANSWER, that by the principles premised we are not deprived of any one thing in nature. Whatever we see, feel, hear, or anywise conceive or understand remains as secure as ever.

SECOND OBJECTION. - It will be OBJECTED that there is a great difference betwixt imagining oneself burnt, and actually being so. To which the answer is that nobody will pretend that real pain can possibly be without the mind.

THIRD OBJECTION - It will be objected that we see things at distance which consequently do not exist in the mind. In answer that in a DREAM we do oft perceive things as existing, and yet those things are acknowledged to have their existence only in the mind.

FOURTH OBJECTION. - It will be objected that from the foregoing it follows things are every moment annihilated and created anew. The trees therefore are in the garden, or the chairs in the parlour, no longer than there is somebody to perceive them. Upon SHUTTING MY EYES all the furniture in the room is reduced to nothing, and upon opening them it is again created. In ANSWER to all which, I ask the reader whether he means anything by the actual existence of an idea distinct from its being perceived.

OBJECTIONS DERIVED FROM THE SCRIPTURES ANSWERED. - Some there are who think that the Holy Scriptures are so clear in the point as will sufficiently convince every good Christian that bodies do really exist; there being in Holy Writ innumerable facts related which evidently suppose the reality of timber and stone, mountains and rivers, and cities, and human bodies. To which I answer that no sort of writings whatever, sacred or profane, which use those and the like words in the vulgar acceptation, or so as to have a meaning in them, are in danger of having their truth called in question by our doctrine. And I do not think that what philosophers call Matter, or the existence of objects without the mind, is anywhere mentioned in Scripture. It will be urged that miracles do, at least, lose much of their stress and import by our principles. What must we think of Moses' rod? was it not really turned into a serpent; or was there only a change of ideas in the minds of the spectators? And, can it be supposed that our Saviour did no more at the marriage-feast in Cana than impose on the sight, and smell, and taste of the guests, so as to create in them the appearance or idea only of wine? The same may be said of all other miracles; which, in consequence of the foregoing principles, must be looked upon only as so many cheats, or illusions of fancy. To this I reply, that the rod was changed into a real serpent, and the water into real wine. This does not in the least contradict what I have elsewhere said.

THE REMOVAL OF MATTER GIVES CERTAINTY TO KNOWLEDGE. - From the principles we have laid down it follows human knowledge may naturally be reduced to two heads - that of ideas and that of spirits. So long as we attribute a real existence to unthinking things, distinct from their being perceived, it is not only impossible for us to know with evidence the nature of any real unthinking being, but even that it exists. Hence it is that we see philosophers distrust their senses, and doubt of the existence of heaven and earth, of everything they see or feel, even of their own bodies. But, all this doubtfulness, which so bewilders and confounds the mind and makes philosophy ridiculous in the eyes of the world, vanishes if we annex a meaning to our words.

SENSIBLE QUALITIES REAL. - It were a mistake to think that what is here said derogates in the least from the reality of things. All the difference is that, according to us, the unthinking beings perceived by sense have no existence distinct from being perceived, and cannot exist in any other substance than those unextended indivisible substances or spirits which act and think and perceive them.

OBJECTIONS OF ATHEISTS OVERTURNED. - For, as we have shown the doctrine of Matter or corporeal substance to have been the main pillar and support of Scepticism, and all the impious schemes of Atheism and Irreligion. All their monstrous systems have so visible and necessary a dependence on it that, when this corner-stone is once removed, the whole fabric cannot choose but fall to the ground.

OF IDOLATORS. - The existence of Matter, or bodies unperceived, has not only been the main support of Atheists and Fatalists, but on the same principle doth Idolatry likewise in all its various forms depend. Did men but consider that the sun, moon, and stars, and every other object of the senses are only so many sensations in their minds, which have no other existence but barely being perceived, doubtless they would never fall down and worship their own ideas, but rather address their homage to that ETERNAL INVISIBLE MIND which produces and sustains all things.

We next treat of SPIRITS. By the word spirit we mean only that which thinks, wills, and perceives; this, and this alone, constitutes the signification of the term. But it will be objected that, if there is no idea signified by the terms soul, spirit, and substance, they are wholly insignificant, or have no meaning in them. I answer, those words do mean or signify a real thing; that what I am myself, that which I denote by the term I, is the same with what is meant by soul or spiritual substance.

THE NATURAL IMMORTALITY OF THE SOUL IS A NECESSARY CONSEQUENCE OF THE FOREGOING DOCTRINE. - It must not be supposed that they who assert the natural immortality of the soul are of opinion that it is incapable of annihilation by the Creator, but only that it is not liable to be broken or dissolved by the ordinary laws of nature or motion. They indeed who hold the soul of man to be only a system of animal spirits, make it perishing and corruptible as the body; since such a being could not survive the ruin of the tabernacle wherein it is enclosed. And this notion has been greedily embraced and cherished by the worst part of mankind, as the most effectual antidote against all impressions of virtue and religion. But we have shown that the soul is indivisible, incorporeal, unextended, and it is consequently incorruptible; that is to say, "the soul of man is naturally immortal."

It is evident to every one that those things which are called the Works of Nature, that is, the far greater part of the ideas or sensations perceived by us, are not produced by, or dependent on, the wills of men. There is therefore some other Spirit that causes them; I say if we consider all these things, and at the same time attend to the meaning and import of the attributes One, Eternal, Infinitely Wise, Good, and Perfect, we shall clearly perceive that they belong to the aforesaid Spirit, "who works all in all," and "by whom all things consist."

THE EXISTENCE OF GOD MORE EVIDENT THAN THAT OF MAN. - Hence, it is evident that God is known as certainly and immediately as any other mind or spirit whatsoever distinct from ourselves. It seems to be a general pretence of the unthinking herd that they cannot see God. Could we but see Him, say they, as we see a man, we should believe that He is, and believing obey His commands. But alas, we need only open our eyes to see the Sovereign Lord of all things, with a more full and clear view than we do any one of our fellow-creatures. But when we see the colour, size, figure, and motions of a man, we perceive only certain sensations or ideas excited in our own minds. And after the same manner we see God; whithersoever we direct our view, we do at all times and in all places perceive manifest tokens of the Divinity.

That the discovery of this great truth, which lies so near and obvious to the mind, should be attained to by the reason of so very few, is a sad instance of the stupidity and inattention of men, who, though they are surrounded with such clear manifestations of the Deity, are yet so little affected by them that they seem, as it were, blinded with excess of light.

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