George Berkeley was an Irish philosopher and Anglican bishop who developed one of the most radical and counterintuitive philosophical positions in Western thought.^[1] Born in County Kilkenny, Ireland, Berkeley was educated at Trinity College Dublin, where he later became a fellow and lecturer.

Berkeley is best known for his idealist philosophy, summarized in the Latin phrase “esse est percipi” (to be is to be perceived). Writing in the early 18th century during the height of the Enlightenment, Berkeley challenged the emerging scientific materialism of his day by arguing that material objects have no existence independent of being perceived by minds.

Berkeley’s philosophy was motivated partly by religious concerns—he saw materialism as leading to skepticism and atheism. By arguing that the physical world exists only as ideas in minds (ultimately in God’s mind), he aimed to refute both materialist atheism and skeptical doubt about the external world.

Though his contemporaries often dismissed his views as absurd, Berkeley’s arguments were philosophically sophisticated and have had lasting influence. His critique of abstract ideas, his analysis of perception, and his challenge to the primary/secondary quality distinction anticipated many later developments in philosophy.

OF THE PRINCIPLES OF HUMAN KNOWLEDGE

1. 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 else such as are perceived by attending to the passions and operations of the mind; or lastly, ideas formed by help of memory and imagination–either compounding, dividing, or barely representing those originally perceived in the aforesaid ways. By sight I have the ideas of light and colours, with their several degrees and variations. By touch I perceive hard and soft, heat and cold, motion and resistance, and of all these more and less either as to quantity or degree. Smelling furnishes me with odours; the palate with tastes; and hearing conveys sounds to the mind in all their variety of tone and composition. And as several of these are observed to accompany each other, they come to be marked by one 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.

3. 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. And it seems no less evident that the various sensations or ideas imprinted on the sense, however blended or combined together (that is, whatever objects they compose), cannot exist otherwise than IN a mind perceiving them. I think an intuitive knowledge may be obtained of this by any one that shall attend to WHAT IS MEANT BY THE TERM EXIST, when applied to sensible things. The table I write on I say exists, that is, I see and feel it; and if I were out of my study I should say it existed–meaning thereby that if I was in my study I might perceive it, or that some other spirit actually does perceive it.[Note.] There was an odour, that is, it was smelt; there was a sound, that is, it was heard; a colour or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions. For as to what is said of the absolute existence of unthinking things without any relation to their being perceived, that seems perfectly unintelligible. Their ESSE is PERCIPI, nor is it possible they should have any existence out of the minds or thinking things which perceive them.

4. THE VULGAR OPINION INVOLVES A CONTRADICTION.–It is indeed an opinion STRANGELY prevailing amongst men, that houses, mountains, rivers, and in a word all sensible objects, have an existence, natural or real, distinct from their being perceived by the understanding. But, with how great an assurance and acquiescence soever this principle may be entertained in the world, yet whoever shall find in his heart to call it in question may, if I mistake not, perceive it to involve a manifest contradiction. For, what are the fore-mentioned objects but the things we perceive by sense? and what do we PERCEIVE BESIDES OUR OWN IDEAS OR SENSATIONS? and is it not plainly repugnant that any one of these, or any combination of them, should exist unperceived?

5. CAUSE OF THIS PREVALENT ERROR.–If we thoroughly examine this tenet it will, perhaps, be found at bottom to depend on the doctrine of ABSTRACT IDEAS. For can there be a nicer strain of abstraction than to distinguish the existence of sensible objects from their being perceived, so as to conceive them existing unperceived? Light and colours, heat and cold, extension and figures–in a word the things we see and feel–what are they but so many sensations, notions, ideas, or impressions on the sense? and is it possible to separate, even in thought, any of these from perception? For my part, I might as easily divide a thing from itself. I may, indeed, divide in my thoughts, or conceive apart from each other, those things which, perhaps I never perceived by sense so divided. Thus, I imagine the trunk of a human body without the limbs, or conceive the smell of a rose without thinking on the rose itself. So far, I will not deny, I can abstract–if that may properly be called ABSTRACTION which extends only to the conceiving separately such objects as it is possible may really exist or be actually perceived asunder. But my conceiving or imagining power does not extend beyond the possibility of real existence or perception. Hence, as it is impossible for me to see or feel anything without an actual sensation of that thing, so is it impossible for me to conceive in my thoughts any sensible thing or object distinct from the sensation or perception of it.[Note.]

6. Some truths there are so near and 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 their BEING (ESSE) is to be perceived or known; 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–it being perfectly unintelligible, and involving all the absurdity of abstraction, to attribute to any single part of them an existence independent of a spirit [Note.]. To be convinced of which, the reader need only reflect, and try to separate in his own thoughts the being of a sensible thing from its being perceived.

18. THE EXISTENCE OF EXTERNAL BODIES WANTS PROOF.–But, though it were possible that solid, figured, movable substances may exist without the mind, corresponding to the ideas we have of bodies, yet HOW IS IT POSSIBLE FOR US TO KNOW THIS? Either we must know it by sense or by reason. As for our senses, by them we have the knowledge ONLY OF OUR SENSATIONS, ideas, or those things that are immediately perceived by sense, call them what you will: but they do not inform us that things exist without the mind, or unperceived, like to those which are perceived. This the materialists themselves acknowledge. It remains therefore that if we have any knowledge at all of external things, it must be by REASON, inferring their existence from what is immediately perceived by sense. But what reason can induce us to believe the existence of bodies without the mind, from what we perceive, since the very patrons of Matter themselves do not pretend there is ANY NECESSARY CONNEXION BETWIXT THEM AND OUR IDEAS? I say it is granted on all hands (and what happens in dreams, phrensies, and the like, puts it beyond dispute) that IT IS POSSIBLE WE MIGHT BE AFFECTED WITH ALL THE IDEAS WE HAVE NOW, THOUGH THERE WERE NO BODIES EXISTING WITHOUT RESEMBLING THEM. Hence, it is evident the supposition of external bodies is not necessary for the producing our ideas; since it is granted they are produced sometimes, and might possibly be produced always in the same order, we see them in at present, without their concurrence.

25. THIRD ARGUMENT.[Note: Vide sect. iii. and vii.]–REFUTATION OF LOCKE.–All our ideas, sensations, notions, or the things which we perceive, by whatsoever names they may be distinguished, are visibly inactive–there is nothing of power or agency included in them. So that ONE IDEA or object of thought CANNOT PRODUCE or make ANY ALTERATION IN ANOTHER. To be satisfied of the truth of this, there is nothing else requisite but a bare observation of our ideas. For, since they and every part of them exist only in the mind, it follows that there is nothing in them but what is perceived: but whoever shall attend to his ideas, whether of sense or reflexion, will not perceive in them any power or activity; there is, therefore, no such thing contained in them. A little attention will discover to us that the very being of an idea implies passiveness and inertness in it, insomuch that it is impossible for an idea to do anything, or, strictly speaking, to be the cause of anything: neither can it be the resemblance or pattern of any active being, as is evident from sect. 8. Whence it plainly follows that extension, figure, and motion cannot be the cause of our sensations. To say, therefore, that these are the effects of powers resulting from the configuration, number, motion, and size of corpuscles, must certainly be false. [Note: Vide sect. cii.]

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Berkeley, George, A Treatise Concerning the Principles of Human Knowledge,  (Project Gutenberg, 2006), https://www.gutenberg.org/files/4723/4723-h/4723-h.htm.

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