George Berkeley


George Berkeley (1685 – 1753) — known as Bishop Berkeley, Anglo-Irish Anglican bishop (Bishop of Cloyne) — was a philosopher, and a scientist, best known for his empiricist and idealist philosophy, which holds that reality consists only of minds and their ideas; everything save the spiritual exists only insofar as it is perceived by the senses.

His primary achievement was the advancement of a theory he called "immaterialism" (later referred to as "subjective idealism" by others). This theory denies the existence of material substance and instead contends that familiar objects like tables and chairs are only ideas in the minds of perceivers and, as a result, cannot exist without being perceived. Berkeley is also known for his critique of abstraction, an important premise in his argument for immaterialism.

In 1709, Berkeley published his first major work, An Essay towards a New Theory of Vision, in which he discussed the limitations of human vision and advanced the theory that the proper objects of sight are not material objects, but light and colour. This foreshadowed his chief philosophical work, A Treatise Concerning the Principles of Human Knowledge, in 1710, which, after its poor reception, he rewrote in dialogue form and published under the title Three Dialogues between Hylas and Philonous in 1713.
(Wikipedia & New World Encyclopedia)

George Berkeley (1685—1753) was one of the three most famous British Empiricists. (The other two are John Locke and David Hume.) Berkeley is best known for his early works on vision (An Essay towards a New Theory of Vision, 1709) and metaphysics (A Treatise concerning the Principles of Human Knowledge, 1710; Three Dialogues between Hylas and Philonous, 1713).

Berkeley’s empirical theory of vision challenged the then-standard account of distance vision, an account which requires tacit geometrical calculations. His alternative account focuses on visual and tactual objects. Berkeley argues that the visual perception of distance is explained by the correlation of ideas of sight and touch. This associative approach does away with appeals to geometrical calculation while explaining monocular vision and the moon illusion, anomalies that had plagued the geometric account.

Berkeley claimed that abstract ideas are the source of all philosophical perplexity and illusion. In his Introduction to the Principles of Human Knowledge he argued that, as Locke described abstract ideas (Berkeley considered Locke’s the best account of abstraction), (1) they cannot, in fact, be formed, (2) they are not needed for communication or knowledge, and (3) they are inconsistent and therefore inconceivable.

In the Principles and the Three Dialogues Berkeley defends two metaphysical theses: idealism (the claim that everything that exists either is a mind or depends on a mind for its existence) and immaterialism (the claim that matter does not exist). His contention that all physical objects are composed of ideas is encapsulated in his motto esse est percipi (to be is to be perceived).
(Internet Encyclopedia of Philosophy)

Concluding Remarks

According to Berkeley, the world consists of nothing but minds and ideas.
Ordinary objects are collections of ideas.
In his discussion of vision, he argued that one learns to coordinate ideas of sight and touch to judge distance, magnitude, and figure, properties which are immediately perceived only by touch. The ideas of one sense become signs of ideas of the other senses.
In his philosophical writings, this coordination of regularly occurring ideas becomes the way the world is known and the way humans construct real things.
If there are only minds and ideas, there is no place for some scientific constructs. Newtonian absolute space and time disappear. Time becomes nothing but the succession of ideas in individual minds (PHK §98). Motion is entirely object-relative (PHK §§112-117). Science becomes nothing more than a system of natural signs.
With the banishing of abstraction, mathematics is reduced to a system of signs in which words or numerals signify other words or numerals (PHK §122). Space is reduced to sensible extension, and since one cannot actually divide a piece of extension into an infinite number of sensible parts, various geometrical paradoxes dissolve. As Berkeley understands them, science and Christian theology become compatible.
(Internet Encyclopedia of Philosophy: George Berkeley #Concluding Remarks)


Causation and Volition

Berkeley’s target was Descartes’ view of the world as elaborated by Locke and the scientist Robert Boyle. In this view, the physical world is made up of a vast number of physical particles, or “corpuscles”, whose nature and interactions give rise to the world as we understand it. More controversially, for Berkeley, this view also maintains that the world causes the perceptual ideas we have of it by the way it interacts with our senses.
Berkeley has two main objections to this view. First, he argues that our understanding of causality is based entirely on our experience of our own volitions (the way we cause events to happen through the action of our wills). ………… Berkeley maintains that there is no such thing as a “physical cause”, because there is no such thing as a physical world beyond the world of ideas that could possibly be the cause of our ideas. The only type of cause that there is in the world, according to Berkeley, is precisely the volitional kind of cause that is the exercise of the will.

Berkeley’s second objection is that because ideas are mental entities, there cannot resemble physical entities, because the two types of thing have completely different properties. A painting or a photograph can resemble a physical object because it is itself a physical thing, but to think of an idea as resembling a physical object is to mistake it for a physical thing itself. Ideas, then, can only resemble other ideas. And as our only experience of the world comes through our ideas, any claim that we can even understand the notion of “physical things” is mistaken. What we are really understanding are mental things. The world is constructed purely of thought, and whatever is not itself perceiving, exists only as one of our perceptions.
(www.dk.com The Philosophy Book (2011), p 140)

 

Treatise Concerning Principles of Human Knowledge

This book largely seeks to refute the claims made by Berkeley's contemporary John Locke about the nature of human perception. Whilst, like all the Empiricist philosophers, both Locke and Berkeley agreed that we are having experiences, regardless of whether material objects exist, Berkeley sought to prove that the outside world is composed solely of ideas. Berkeley did this by suggesting that "Ideas can only resemble Ideas" - the mental ideas that we possess can only resemble other ideas (not material objects) and thus the external world consists not of physical form, but rather of ideas. This world is given logic and regularity by some other force, which Berkeley concludes is God. (Wikipedia: A Treatise Concerning the Principles of Human Knowledge)
In the Introduction to the Principles of Human Knowledge, Berkeley laments the doubt and uncertainty found in philosophical discussions, and he attempts to find those principles that drew philosophy away from common sense and intuition. He finds the source of skepticism in the theory of abstract ideas, which he criticizes. (Internet Encyclopedia of Philosophy)


The Principles of Human Knowledge

(George Berkeley's "Treatise Concerning Principles of Human Knowledge")

Introduction

1 Philosophy is just the study of wisdom and truth, most time and care on it would enjoy a greater calm and serenity of mind, know things more clearly and certainly, and be less disturbed with doubts and difficulties than other men. But what we find is quite different, namely that the illiterate majority of people, who walk the high road of plain common sense and are governed by the dictates of nature, are mostly comfortable and undisturbed. To them nothing that is familiar appears hard to explain or to understand. They don’t complain of any lack of certainty in their senses, and are in no danger of becoming sceptics. But as soon as we depart from sense and instinct to follow the light of a higher principle—i.e. to reason, meditate, and reflect on the nature of things—a thousand doubts spring up in our minds concerning things that we previously seemed to understand fully. We encounter many prejudices and errors of the senses; and when we try to correct these by reason, we are gradually drawn into crude paradoxes, difficulties, and inconsistencies that multiply and grow on us as our thoughts progress; until finally, having wandered through many intricate mazes, we find ourselves back where we started or—which is worse—we sit down in a forlorn scepticism.
4 My purpose therefore is to try to discover what the underlying sources are of all that doubtfulness and uncertainty, those absurdities and contradictions. ….. ……

6 You will understand the rest of this work more easily if I begin by discussing the nature of language and how it can be misused. I need especially to attend to a doctrine that seems to have played a large part in making people’s theories complex and confusing, and to have caused endless errors and difficulties in most branches of knowledge. I am referring to the theory that the mind has a power of forming abstract ideas or notions of things. Anyone who knows anything about the writings and disputes of philosophers must realize that a great part of them is spent on abstract ideas, which are thought to be especially the object of the sciences of logic and metaphysics, and of all learning of the supposedly most abstracted and elevated kind. In all of these studies, almost every discussion assumes that there are abstract ideas in the mind, and that it is quite familiar with them.

7 Everyone agrees that the qualities of things never really exist in isolation from one another; rather, they are mixed and blended together, several in the same object. But, we are told by the supporters of ‘abstract ideas’, the mind can consider each quality on its own, abstracted from the others with which it is united in the object, and in that way the mind forms abstract ideas. For example, your eyesight presents you with an object that is extended, coloured, and moving; and your mind resolves this mixed or compound idea into its simple, constituent parts, and views each in isolation from the rest; which is how it forms the abstract ideas of extension, of colour, and of motion. It isn’t possible for colour or motion to exist without extension: but according to these ‘abstract idea’ theorists the mind can by abstraction form the idea of colour without extension, and of motion without either colour or extension.

8 [This section continues to expound the theory of abstract ideas, in preparation for an attack on it.]
Again, the mind observes that the extended things that we perceive by sense, although they vary in size, shape and so on, also all have something in common; and it singles out and isolates the common element, thereby forming a highly abstract idea of extension. This is neither line, surface, nor solid, and it has no particular shape or size; it is an idea entirely separated out from all these features that distinguish extended things from one another•. Similarly the mind can leave out all the differences amongst the colours that are seen, retaining only what is common to them all; and in this way it makes an idea of colour, which is not red, blue, white or any other specific colour. Again, by considering motion on its own—separated out not only from the body that moves but also from how it moves, in what direction and how fast—the mind forms an abstract idea of motion, which is equally applicable to all particular movements that we can perceive through our senses—the movement of a beckoning finger and the movement of Venus around the sun.

9 [The exposition of the theory of abstract ideas continues, becoming increasingly sarcastic in tone.]
The kind of mental separation through which the mind forms abstract ideas of qualities taken singly also enables it to achieve abstract ideas of more complex items each of which includes a number of qualities that exist together in a single object. For example, having observed that Peter, James, and John have certain features of shape etc. in common, the mind forms a complex idea that leaves out whatever differentiates these men from one another or from other men, and retains only what is common to all; and in this way it makes an abstract idea that applies equally to all men, excluding any details that might tie it down to any one man in particular. This (they say) is how we come to have the abstract idea of man (or of humanity or human nature, if you like). This idea includes colour, because every man has some colour; but then it can be neither white, nor black, nor any particular colour, because there is no one colour that all men have. The idea also includes height because every man has some height or other, but it is neither tall nor short nor middling, but something abstracted from all these because there is no one height that all men have. Similarly for all the rest.
Furthermore, many sorts of creatures correspond in some ways but not all to the complex idea of man; and the mind, leaving out the features that are special to men and retaining only the ones that are shared by all the living creatures, forms the idea of animal. This abstracts not only from all particular men, but also all birds, beasts, fishes, and insects. The constituent parts of the abstract idea of animal are body, life, sense, and spontaneous motion [= ‘the ability to move without being pushed or pulled’]. By ‘body’ is meant body without any particular shape or size, because no one shape or size is common to all animals. The idea doesn’t include any specific kind of covering—hair or feathers or scales, etc.—but nor does it specify bare skin; for various animals differ in respect of whether they have hair, feathers, scales, or bare skin, so that all those differences must be left out of the abstract idea of animal. For the same reason, the spontaneous motion must not be walking, flying or creeping; but it is a motion all the same. What kind of motion it can be isn’t easy to conceive.
10 Whether others have this amazing ability to form abstract ideas, they will know better than I. Speaking for myself: I find that I do indeed have a capacity for imagining— representing to myself the ideas of particular things that I have perceived—and of splitting those ideas up and reassembling them in various ways. I can imagine a man with two heads, or the upper parts of a man joined to the body of a horse. I can consider the hand, the eye, the nose, each by itself abstracted or separated from the rest of the body. But then whatever hand or eye I imagine, it must have some particular shape and colour. Similarly, any idea that I form of a man must be of a specific kind of man: he must be white or black or brown, straight or crooked, tall or short or middling. Try as I may, I can’t get into my mind the abstract idea of man that is described in the preceding section. And I find it equally impossible to form an abstract idea of motion that leaves out the thing that moves and is neither swift nor slow, curved nor straight. The same holds for absolutely all abstract ideas. I freely admit that I can perform ‘abstraction’ in a certain sense, namely: when several parts or qualities are united in an object, I can have the thought of one of them separated from the others if it could really exist apart from them. But I deny that I can perform ‘abstraction’ in the standard meaning of that word, which covers two kinds of mental performance: (1) conceiving abstractly and in isolation a quality that couldn’t exist in isolation as we are said to do with colour and motion; and (2) forming a general notion by abstracting from particulars in the way I have described, as we are said to do with man and animal. There is reason to think that most people are like me in this respect. The majority of people, who are simple and illiterate, never claim to have abstract notions. Such notions are described by those who believe in them• as difficult to form; it takes hard work, we are told, to make an abstract idea. So we can reasonably conclude that if there are any abstract ideas they are all in the minds of learned people.

11. Locke suggested that the biggest intellectual difference between man and beast is that men can form abstract ideas while beasts cannot. ……..
I readily agree with Locke that brutes have no capacity for abstraction. But if that’s our criterion for whether something is a brute, I am afraid that many who are accepted as men should be counted among the brutes! We have no evidence that brutes have abstract general ideas, Locke said, because we don’t observe them using words or other general signs. He was assuming that one can’t use words unless one has general ideas; which implies that men who use language can abstract or make their ideas general. That Locke was thinking along these lines can be seen in how he answered his own question: ‘Since all things that exist are only particulars, how do we come by general terms?’ His answer was, ‘Words become general by being made the signs of general ideas’ (III.iii.6). But I maintain, on the contrary, that it seems that a word becomes general by being made the sign not of one abstract general idea but of many particular ideas, any one of which it may suggest to the mind. Consider for example the propositions A thing’s change of motion is proportional to the force that is exerted on it, and Whatever is extended can be divided. These axioms are to be understood as holding for motion and extension in general; but that doesn’t imply that they suggest to my thoughts
        •an idea of motion without a body moved, and with no determinate direction or velocity,
or that I must conceive
        •an abstract general idea of extension, which is not line or surface or solid, not large or small, not black or white or red or of any other determinate colour.

All that is needed is that the first axiom is true for every motion that I consider, whether it be swift or slow, perpendicular or horizontal or oblique, and in whatever object; and that the second axiom holds for every specific extension, whether line or surface or solid, and whether of this or that size or shape.

12 We shall be better placed to understand what makes a word a general term if we first understand how ideas become general. (I emphasize that I don’t deny that there are general ideas—only that there are abstract general ideas. In the passages I have quoted, every mention of general ideas carries the assumption that they are formed by abstraction in the manner described in 7 and 9 above.) If we want to speak meaningfully and not say things that we can’t make sense of, I think we shall agree to the following. An idea, which considered in itself is particular, becomes general in its meaning by being made to represent or stand for all other particular ideas of the same sort as itself. …….., And the word is general for the same reason—namely that it stands equally well for each and every particular.

13 To give you a still clearer view of what abstract ideas are supposed to be like, and of how we are supposed to need them, I shall quote one more passage from the Essay Concerning Human Understanding:

For children and others whose minds have not yet been put to work much, abstract ideas aren’t as easy to form as particular ones are. If adults find them easy, that is only because they have had so much practice. For when we reflect carefully and in detail on them, we’ll find that general ideas are mental fictions or contrivances that are quite difficult to construct; we don’t come by them as easily as we might think. The general idea of a triangle, for example, though it isn’t one of the most abstract, comprehensive, and difficult ideas, can’t be formed without hard work and skill. For that idea must be neither oblique nor rectangle, neither equilateral, equicrural, nor scalenon, but all and none of these at once. In effect, it is something imperfect that cannot exist, an idea in which parts of several different and inconsistent ideas are put together. It is true that because of our imperfect human condition, the mind needs such ideas for two of its main purposes—communication, and the growth of knowledge—so it moves as fast as it can to get them. Still, there is reason to suspect that such ideas indicate how imperfect we are. Anyway, what I have said is enough to show that the ideas that come earliest and most easily to the mind aren’t abstract and general ones, and that our earliest knowledge doesn’t involve them. (IV.vii.9)


If anyone thinks he can form in his mind an idea of a triangle such as the one described in that passage, I shan’t waste my time trying to argue him out of it. I merely ask you, the reader, to find out for sure whether you have such an idea. This can’t be very difficult. What is easier than for you to look a little into your own thoughts and discover whether you do or can have an idea that fits the description we have been given of the general idea of a triangle—‘neither oblique nor rectangle, neither equilateral, equicrural, nor scalenon, but all and none of these at once’?

14 Much is said by Locke about how difficult abstract ideas are—about the care and skill that is needed in forming them. And everyone agrees that it takes hard mental work to free our thoughts from particular objects and raise them to the level of theorizing that involves abstract ideas. It would seem to follow that the forming of abstract ideas is too difficult to be necessary for communication. …….

15 Abstract ideas are no more needed, in my opinion, for the growth of knowledge than they are for communication. I entirely agree with the widespread belief that all knowledge and demonstration concerns universal notions; but I can’t see that those are formed by abstraction. ….. When I prove a proposition about triangles, for instance, I am of course employing the universal idea of a triangle; but that doesn’t involve me in thinking of a triangle that is neither equilateral nor scalenon nor equicrural! All it means is that the particular triangle I have in mind, no matter what kind of triangle it may be, is ‘universal’ in the sense that it equally stands for and represents all triangles whatsoever. All this seems to be straightforward and free of difficulties.

16 You may want to make this objection:
“How can we know any proposition to be true of all particular triangles unless we first see it demonstrated of the abstract idea of a triangle that fits all the particular ones? Just because a property can be demonstrated to belong to some one particular triangle, it doesn’t follow that it equally belongs to any other triangle that differs in some way from the first one. ……..
For example, having demonstrated of an isosceles right-angled triangle that its three angles are equal to two right ones, I can’t conclude from this that the same holds for all other triangles that don’t have a right angle and two equal sides.”
To this I answer that although the idea I have in view while I make the demonstration may be (for instance) that of an isosceles right-angled triangle whose sides are of a determinate length, I can still be certain that it applies also to all other triangles, no matter what their sort or size. I can be sure of this because neither the right angle nor the equality of sides nor length of the sides has any role in the demonstration……..
I conclude the proposition holds for all triangles, having demonstrated it in a certain way to hold for a particular right-angled isosceles triangle. … [I don’ need] the abstract idea of a triangle!
I don’t deny that a man can abstract, in that he can consider a figure merely as triangular without attending to the particular qualities of the angles or relations of the sides. But that doesn’t show that he can form an abstract general inconsistent idea of a triangle. Similarly, because all that is perceived is not considered, we may think about Peter considered as a man, or considered as an animal, without framing the abstract idea of man or of animal.

The advancement of knowledge has been pursued with great care, hard work, and high abilities, and yet most branches of knowledge remain full of darkness and uncertainty, and of disputes that seem likely never to end; ………
Perhaps this will cease when we have a view of the false principles that people have accepted, of which I think the one that has had the widest influence over the thoughts of enquiring and theory-building men is the doctrine of abstract general ideas.

18 This prevailing view about abstract ideas seems to me to have its roots in language. 21 I think I have shown the impossibility of abstract ideas. ….. and have tried to show they are of no use for the purposes for which they are thought to be necessary. And, lastly, I have traced them to their source, which appears to be language.
It can’t be denied that words are extremely useful: they make it possible for all the knowledge that has been gained by the enquiries of men at many times and in all nations to be pulled together and surveyed by a single person. But at the same time it must be admitted that most branches of knowledge have been made enormously much darker and more difficult by the misuse of words and turns of phrase. Therefore, since words are so apt to influence our thoughts, when I want to consider any ideas I shall try to take them bare and naked, keeping out of my thoughts—as much as I can—the names that those ideas have been given through long and constant use. From this I expect to get the following three advantages:

22 •First, I shall be sure to keep clear of all purely verbal controversies—those weeds whose springing up, in almost all branches of knowledge, has been a principal hindrance to the growth of true and sound knowledge.
•Secondly, this seems to be a sure way to extricate myself from that fine and delicate net of abstract ideas, which has so miserably perplexed and entangled the minds of men.
•Thirdly, so long as I confine my thoughts to my own ideas with the words peeled off, I don’t see how I can easily be mistaken.

The objects that I consider are all ones that I clearly and adequately know: I can’t fall into error by thinking I have an idea that I really don’t have, or by imagining that two of my own ideas are alike (or that they are unalike) when really they are not. To observe how my ideas agree or disagree, and to see which ideas are included in any compound idea and which are not, all I need is to pay attention to what happens in my own understanding.

23 But I can’t get all these advantages unless I free myself entirely from the deception of words. I hardly dare promise myself that, because the union between words and ideas began early and has been strengthened by many years of habit in thought and speech, making it very difficult to dissolve. This difficulty seems to have been very much increased by the doctrine of abstraction. For so long as men thought their words have abstract ideas tied to them, it isn’t surprising that they used words in place of ideas: they found that they couldn’t set aside the word and retain the abstract idea in the mind, because abstract ideas are perfectly inconceivable.
That is the principal cause for the fact that men who have emphatically recommended to others that in their meditations they should lay aside all use of words and instead contemplate their bare ideas have failed to do this themselves.
Recently many people have become aware of the absurd opinions and meaningless disputes that grow out of the misuse of words. And they had given good advice about how to remedy these troubles—namely that we should attend not to the words that signify ideas but rather to the ideas themselves. But however good this advice that they have given others may be, they obviously couldn’t properly follow it themselves so long as they thought that
•the only immediate use of words was to signify ideas, and
•that the immediate signification of every general name was a determinate, abstract idea.

24 But when you know that these are mistakes, you can more easily prevent your thoughts from being influenced by words. Someone who knows that he has only particular ideas won’t waste his time trying to conceive the abstract idea that goes with any name. And someone who knows that names don’t always stand for ideas will spare himself the labour of looking for ideas where there are none to be had. So it is desirable that everyone should try as hard as he can to obtain a clear view of the ideas he wants to consider, separating from them all the clothing and clutter of words that so greatly blind our judgment and scatter our attention. In vain do we extend our view into the heavens, and presumably into the entrails of the earth; in vain do we consult the writings of learned men, and trace the dark footsteps of antiquity; we need only draw aside the curtain of words, to behold the fairest tree of knowledge, whose fruit, namely, our ‘bare naked ideas’, is excellent and lies within reach of our hand.

25 Unless we take care to clear the first principles of knowledge from being burdened and deluded by words, we can reason from them for ever without achieving anything; we can draw consequences from consequences and be never the wiser. The further we go, the more deeply and irrecoverably we shall be lost and entangled in difficulties and mistakes. To anyone who plans to read the following pages, therefore, I say: Make my words the occasion of your own thinking, and try to have the same sequence of thoughts in reading that I had in writing. This will make it easy for you to discover the truth or falsity of what I say. You will run no risk of being deceived by my words, and I don’t see how you can be led into an error by considering your own naked, undisguised ideas.

 

George Berkeley's "Treatise Concerning Principles of Human Knowledge:" A Summary

(Clean Version)

Ideas are just what go on in the minds, perceptions, thoughts and imaginations.
Ideas couldn’t exist without minds. If no minds exist to perceive things, there won’t be any idea of things. If minds do not exist, there won’t be idea (sensation) of pain of getting burned. Nothing.

So, why do people think that thing exists outside the mind? That doesn’t make sense. Here are the things that we know exist: the things we perceive; and ‘things’ are as they are as we perceive them. Want proof? Just try to think of something that exists without existing in a mind somewhere.

There’s no way to separate existence from being perceived by something. You just can’t do it. It can’t be done. So, nothing exists without being some kinds of idea.

John Locke’s “primary qualities” are supposed to not exist in the mind. Extension? You only know the stairs are extended when you bang your toe on them. Figure? Just try to describe a figure of a thing without talking about ideas. Movement? “How do you know it moved?” “Well, I saw it over there. And now, I see it over in that other place.” More ideas. Locke is wrong.

And what’s all this about “matter”? What grounds could there possibly be for believing that’s true? “You know… feel this chair. Feels solid, right?” Yeah, but that’s an idea, the idea of the solidity of the chair. That’s a thing you perceive. But you can’t perceive matter.

Let’s pretend this “matter” exists, and it’s not at all mental. Then how is it supposed to put ideas in our heads? If it’s completely not perceivable or an idea, if it has no mental qualities, then how does it interact with my mind? So, “matter” doesn’t really even get us anywhere. It doesn’t even answer the questions it’s supposed to help answer. It’s useless.

But still people cling to their ideas. “I just mean the thing itself! Not the sight or the feeling of the chair, the chair thing-in-itself.” But, what could that word possibly be referring to? We’re talking about a thing that’s right in front of us, but you want me to believe you mean something that is not any of the obvious ways I know the chair exists? That’s insane.

We use words in weird ways sometimes. We talk about things causing other things, and things moving from one point to another, but, you know, that’s just the way we talk. That’s not necessarily how things are, that’s just the system we’ve developed to discuss all this stuff. It would be painful o say, “Yes, after the idea of that ball hitting the other ball will come the idea of the other ball moving away from the idea of the first ball.” Go ahead and talk simply, as long as you know what’s really going on.

So where do ideas come from? Obviously there are some things that aren’t ideas. For example, you’re not an idea. You have ideas, but you’re a mind. So, I’m not saying there aren’t substances, I’m just saying, that it’s not physical. Since physical things cannot cause us to have ideas. And since we don’t decide what we can and can’t perceive, there’s got to be some mind out there who puts the ideas in our minds. And that is… God.

In fact, God does all kinds for us. For example, he keeps things existing when no one else perceives them. “What if no one is looking at the table? Does it just go away? "No, it’s there, because it exists in the mind of God.

God keeps the world orderly for us. That’s why we have the laws of nature. How did we get those? We observed them, and that’s how. Kepler observed the movement of the planets, "I think we’re wrong about the “circle’ thing…” so he fixed the rules up. Totally observation is how we get any of the laws. We just come up with ways to describe how ideas seem to proceed.

It doesn’t mean nothing is real. The ideas that you sense are very real. Stick your hand in a fire and you get an idea of pain. And it is a real idea.

Look, people think, “I see a tree, but I didn’t want to see a tree, it just happened! So there must be a thing outside my mind that is a tree!”
But if you think about it that just does not make any sense at all. We have no grounds to believe that anything other than minds and ideas exist, because ideas are all we’ve ever encountered and only minds can encounter ideas. Everything else is just something you pull out of thin imagination because you’re confused.

Descartes wanted to know if anything he perceived is real. It turns out that it’s the only thing that’s real.

 

 

Berkeley's argument for immaterialism

........... has not Locke told us that all our knowledge is derived from sensation? Therefore all our knowledge of anything is merely our sensations of it, and the ideas derived from these sensations. A “thing” is merely a bundle of perceptions – i.e., classified and interpreted sensations. …. The hammer is a bundle of sensations of color, size, shape, weight, touch, etc.; its reality for you is not in its materiality, but in the sensations. If you had no senses, the hammer would not exist for you at all; it might strike your dead thumb forever and yet win from you not the slightest attention. It is only a bundle of sensations, or a bundle of memories; it is a condition of the mind, All matter, so far as we know it, is a mental condition; and the only reality that we know directly is mind.
Source: Will Durant


Immaterialism

No Abstract Ideas
As Berkeley correctly noticed, our experience is always of concrete particulars. When I contemplate the idea of "triangle," the image that comes to mind is that of some determinate shape; having the abstract image of a three-sided figure that is neither equilateral nor isoceles nor scalene is simply impossible.
It is unnecessary, too: for purposes of geometrical reasoning, any particular image can be used as a representative for all.

But the consequence of Berkeley's criticism is a theory of meaning entirely different from Locke's. General terms (or words of any sort) need not signify ideas of their own, on Berkeley's view. Instead, they acquire meaning by a process of association with particular experiences, which are in turn associated with each other. But of course mere association (as Locke himself had noted with respect to ideas) is not a reliable guide to reality.

Sensible Objects
Berkeley held that what we perceive really is as we perceive it to be. But what we perceive are just sensible objects, collections of sensible qualities, which are themselves nothing other than ideas in the minds of their perceivers. In the Dialogues Berkeley used Lockean arguments about the unreliability of secondary qualities in support of his own, more radical view.

Take heat, for example: does it exist independently of our perception of it? When exposed to great heat I feel a pain that everyone acknowledges to be in me, not in the fire, Berkeley argued, so the warmth I feel when exposed to lesser heat must surely be the same. What is more, if dip both of my hands into a bowl of tepid water after chilling one and warming the other, the water will feel both warm and cold at the same time. Clearly, then, heat as I perceive it is nothing other than an idea in my mind.

Similar arguments and experiments establish that other sensible qualities—colors that vary with changes in ambient light, tastes and smells that change perceptibly when I have a cold, and sounds that depend for their quality on the position of my ears and conditions in the air—are, like heat, nothing but ideas in my mind. But the same considerations apply to primary qualities as well, Berkeley pointed out, since my perception of shape and size depend upon the position of my eyes, my experience of solidity depends upon my sense of touch, and my idea of motion is always relative to my own situation. Locke was correct in his view of secondary qualities but mistaken about primary qualities: all sensible qualities are just ideas.

But sensible objects are nothing more than collections of sensible qualities, so they are merely complex ideas in the minds of those who perceive them. For such ideas, Berkeley held, to be just is to be perceived (in Latin, esse est percipi). There is no need to refer to the supposition of anything existing outside our minds, which could never be shown to resemble our ideas, since "nothing can be like an idea but an idea." Hence, there are no material objects.


Material Substance is Inconceivable
Locke's reference to an "unknown substratum" …. is a pointless assumption, according to Berkeley. Since it is the very nature of sensible objects to be perceived, it would be absurd to suppose that their reality depends in any way upon an imperceptible core. This gives rise to a perfectly general argument against even the possibility of material substance.

According to Berkeley, … the very concept of material substance as a sensible object existing independently of any perception is incoherent. No wonder the representationalist philosophy leads to skepticism. Science without Matter
Galileo's astronomy, Newtonian mechanics, and the chemistry of Boyle all took for granted the existence and operation of physical objects. But Berkeley maintained that natural science, if properly conceived, could proceed and even thrive without assuming that bodies are material substances existing outside the mind.
Berkeley argued in his New Theory of Vision that our apparent perception of distance is a mental invention, easily explained in terms of the content of visual ideas, without any reference to existing material objects. In fact, Berkeley held, our visual and tactile perceptions are entirely independent. What we see and what we touch have nothing to do with each other; we have merely learned by experience to associate each with the other, just as we have learned to associate the appearance, the taste, and the smell of an apple. There is no reason to suppose that all of these qualities inhere in a common material substratum.

Religion
The affinity between immaterialism and traditional religion is somewhat easier to understand. Materialism leads to atheism no less than to skepticism, Berkeley believed, since its belief that bodies exist outside the mind encourages the notion that the physical realm may always have existed independently of any spiritual influence. Immaterialism, by contrast, restores god to a role of central importance, not only as the chief among active thinking substances but also as the source of all sensible objects.

God's existence is made evident by everyday instances of perception, according to Berkeley. Since sensible objects are mind-dependent yet exhibit a persistence and regularity that transcends our perception of them, it follows that there must be a master-perceiver, god, in whose mind they always are. Thus, in the Dialogues, Philonous extols the beauty and majesty of the natural world, attributing them to the power and elegance of the divine mind. This leads to the traditional conception of god as deserving of worship because of the benevolent creation of all that we observe.
(www.philosophypages.com/Garth Kemerling Berkeley: Immaterialism)

 

The attack on representationalist materialism

1 THE CORE ARGUMENT
Berkeley presents the following argument (see Winkler, K. P. (1989). Berkeley: An Interpretation, p138):
(1) We perceive ordinary objects (houses, mountains, etc.).
(2) We perceive only ideas.
Therefore, (3) Ordinary objects are ideas.

The argument is valid, and premise (1) looks hard to deny. What about premise (2)? Berkeley believes that this premise is accepted by all the modern philosophers. In the Principles, Berkeley is operating within the idea-theoretic tradition of the seventeenth and eighteenth centuries. In particular, Berkeley believes that some version of this premise is accepted by his main targets, the influential philosophers Descartes and Locke.

However, Berkeley recognizes that these philosophers have an obvious response available to this argument. This response blocks Berkeley's inference to (3) by distinguishing two sorts of perception, mediate and immediate. Thus, premises (1) and (2) are replaced by the claims that (1′) we mediately perceive ordinary objects, while (2′) we immediately perceive only ideas. From these claims, of course, no idealist conclusion follows.
The response reflects a representationalist theory of perception, according to which we indirectly (mediately) perceive material things, by directly (immediately) perceiving ideas, which are mind-dependent items. The ideas represent external material objects, and thereby allow us to perceive them.

2 THE LIKENESS PRINCIPLE
Berkeley devotes the succeeding sections of the Principles to undermining the representationalist response to his initial argument. In effect, he poses the question: What allows an idea to represent a material object? He assumes, again with good grounds, that the representationalist answer is going to involve resemblance:
Berkeley argues that this supposed resemblance is nonsensical; an idea can only be like another idea.

But why? The closest Berkeley ever comes to directly addressing this question is in his early philosophical notebooks, where he observes that “Two things cannot be said to be alike or unlike till they have been compar'd” (PC 377). Thus, because the mind can compare nothing but its own ideas, which by hypothesis are the only things immediately perceivable, the representationalist cannot assert a likeness between an idea and a non-ideal mind-independent material object. (For further discussion, see Winkler 1989, 145–9.)

If Berkeley's Likeness Principle, the thesis that an idea can only be like another idea, is granted, representationalist materialism is in serious trouble. For how are material objects now to be characterized? If material objects are supposed to be extended, solid, or colored, Berkeley will counter that these sensory qualities pertain to ideas, to that which is immediately perceived, and that the materialist cannot assert that material objects are like ideas in these ways. Many passages in the Principles and Dialogues drive home this point, arguing that matter is, if not an incoherent notion, at best a completely empty one.

3 ANTI-ABSTRACTIONISM
One way in which Berkeley's anti-abstractionism comes into play is in reinforcing this point. Berkeley argues in the “Introduction” to the Principles that we cannot form general ideas in the way that Locke often seems to suggest—by stripping particularizing qualities from an idea of a particular, creating a new, intrinsically general, abstract idea. Berkeley then claims that notions the materialist might invoke in a last-ditch attempt to characterize matter, e.g. being or mere extension, are objectionably abstract and unavailable.


4 WHAT DOES MATERIALISM EXPLAIN?
Berkeley is aware that the materialist has one important card left to play: Don't we need material objects in order to explain our ideas? And indeed, this seems intuitively gripping: Surely the best explanation of the fact that I have a chair idea every time I enter my office and that my colleague has a chair idea when she enters my office is that a single enduring material object causes all these various ideas. Again, however, Berkeley replies by effectively exploiting the weaknesses of his opponents' theories:

        …though we give the materialists their external bodies, they by their own confession are never the nearer knowing how our ideas are produced: since they own themselves unable to comprehend in what manner body can act upon spirit, or how it is possible it should imprint any idea in the mind. 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. (PHK 19)

Firstly, Berkeley contends, a representationalist must admit that we could have our ideas without there being any external objects causing them (PHK 18). (This is one way in which Berkeley sees materialism as leading to skepticism.) More devastatingly, however, he must admit that the existence of matter does not help to explain the occurrence of our ideas. After all, Locke himself diagnosed the difficulty:

Body as far as we can conceive being able only to strike and affect body; and Motion, according to the utmost reach of our Ideas, being able to produce nothing but Motion, so that when we allow it to produce pleasure or pain, or the Idea of a Colour, or Sound, we are fain to quit our Reason, go beyond our Ideas, and attribute it wholly to the good Pleasure of our Maker. (Locke 1975, 541; Essay 4.3.6)

And, when Descartes was pressed by Elizabeth as to how mind and body interact,she rightly regarded his answers as unsatisfactory. The basic problem here is set by dualism: how can one substance causally affect another substance of a fundamentally different kind? In its Cartesian form, the difficulty is particularly severe: how can an extended thing, which affects other extended things only by mechanical impact, affect a mind, which is non-extended and non-spatial? Berkeley's point is thus well taken. It is worth noting that, in addition to undermining the materialist's attempted inference to the best explanation, Berkeley's point also challenges any attempt to explain representation and mediate perception in terms of causation.


Moore’s refutation of Berkeley’s subjective idealism,

Moore’s refutation was of Berkeley’ so-called subjective idealism, a doctrine encapsulated in the formula esse is percipi, meaning that whatever is perceived is mind dependent. Thus, the existence of table, persons, planets, and everything else depends upon their being perceived by some mind. Moore thought this proposition ‘monstrous’ and developed a series of arguments against it. His main argument rests on a distinction between the act of perceiving and the object perceived. The act, he argues, is clearly mind dependent but the entity perceived (say, a blue patch) is not. There is no good reason to believe that its existence has the same status as that of the act. Indeed, he contends, there is good reason to believe the opposite. As a result of Moore’s critique, that form of idealism has more or less vanished from the Western philosophical scene and been replaced by various forms of realism, the doctrine that mind-independent entities exist. Moore called these “material” or “physical” objects. It was a form of this doctrine that he was to defend in his epistemological writings.
GoTo Epistemological Realism

 

 

Berkeley's Rejection of Abstract Ideas

The belief in abstract ideas had led to the supposition that material objects exist and that they are quite different from sensations; the fact is that material objects are nothing but collections of sensations given a common name.

A chief cause of scientific and philosophical confusions, Berkeley believes, is the doctrine of abstract ideas, the theory that the mind can abstract from particular qualities a clearly conceived notion of what is common to them, but which itself is otherwise like none of them, or the mind can separate in thought what cannot be separated in reality.
An example of the first abstraction would be a notion of color which is neither red, blue, green, and so forth, or of extension which has neither size, shape, line, plane, nor surface; an illustration of the second would be an abstract idea of color or motion without extension.

Berkeley finds such abstraction psychological impossible. He challenges the reader to conceive such an idea as that of a triangle with all of the general and yet none of the specific characteristics of triangles; … idea may be general without being abstract; we generalize particular ideas by temporarily disregard their unique features, while our demonstrations concern only features shared, But this universality in function must not ne mistaken for abstract conception; the latter is actually without content and unintelligible.

Berkeley claims that the confused belief in abstract ideas arises from language. ….. Let us attend not to words; let us attend to ideas themselves since these are known directly and we can avoid verbal controversies and errors springing from abstraction.
Berkeley thus applies this conclusion to an analysis of the nature and existence of the objects of knowledge.

The objects of knowledge, Berkeley writes, are ideas of three kinds: 1. Sensations; 2, ideas originating in the mind’s own passions and activities; and 3. Memory and imagination.
Berkeley’s immediate concern is with “sensible” objects. Through sight we know color; through sight and touch we know size and shape; through touch, hardness, through smelling, odors. Certain constant collections of such ideas are considered one object or thing and accordingly named, such as “apple” or “tree”. But obviously perceived ideas required a perceiver, and this is spirit or mind, not itself an idea. Careful examination shows that thoughts and ideas have no existence external to minds; hence “sensible” things or physical objects do not exist apart from their perception in minds – their very “esse is percipi”; for them to be is to be perceived.

Berkeley's Rejection of Abstract Ideas

Berkeley extracts from Locke’s Essay two different accounts of the meanings of general terms. One, which may call the representational theory, is that a general idea is a particular idea which has been made general by being made t stand for all of a kind, in the way in which a geometry teacher draws a particular triangle to represent all triangles. Another, which we may call the eliminative theory, is that a general idea is a particular idea which contains only what is common to all particulars of the same kind:
the abstract idea of man eliminates what is peculiar to Peter, James, and John, and retains only what is common to them all. Thus, the abstract idea of colour contains colour, but no particular colour, stature, but no particular stature, and so on.
There is one passage in which Locke combines features of the two theories, where he explains that it takes pains and skill to form the general idea of a triangle ‘for it must be neither oblique nor rectangle, neither equilateral, equicrural nor scalenon; but all and none of these at once’.

Berkeley protests that this is absurd. “The idea of man that I frame myself must be either of a white, or a black, or a tawny, a straight, or a crooked, a tall, or a low, or a middle-sized man. I cannot by any effort of thought conceive the abstract idea”. If by ‘idea’ Berkeley here means an image, his critism seems mistaken. Mental images do not need to have all the properties of that of which they are images, any more than a portrait on canvas has to represent all the features of the sitter. A dress pattern need not specify the colour of the dress, though any actual dress must have some particular colour. A mental image of a dress of no particular colour is no more problematic than a non-specific pattern. There would, indeed, be something odd about an image which had all colours and no colours at once, as Locke’s triangle had all shapes and no shape at once. But it is unfair to judge Locke’s account by this single rhetorical passage.

 

 

An Essay towards a New Theory of Vision

In 1709, Berkeley published An Essay towards a New Theory of Vision (NTV). This is an empirical account of the perception of distance, magnitude, and figure. The New Theory of Vision does not presuppose immaterialism, and, although Berkeley held that it was connected with his later works, the degree of connection is hotly contested among scholars.

Berkeley's objective in the NTV was "to shew the manner wherein we perceive by sight the distance, magnitude, and situation of objects. Also to consider the difference there is betwixt the ideas of sight and touch, and whether there be any idea common to both senses" (NTV §1).

Berkeley agrees with other writers on optics that distance is not immediately seen (NTV §2) and recounts the positions of earlier writers. Some held that we correlate our current perceptions with earlier perceptions and judge that the objects are distant because we had experienced the large size of intermediate objects, or because the objects which now appear small and faint had earlier appeared large and vigorous (NTV §3). Some, such as Descartes, held that distance is judged by a natural geometry based on the angles between the perceived object and the eyes or on the angles of the rays of light that fall upon the eye (NTV §§4 and 6, and Works 1:237-238; Descartes 1:170). Berkeley rejects those accounts. He believes that one perceives distance mediately, i.e., one perceives one idea by means of perceiving another (NTV §9), for example, one perceives that someone is frightened by perceiving the paleness of her face (NTV §10).
(Internet Encyclopedia of Philosophy)

Berkeley goes on to argue that visual cues are used to indirectly judge distance. Berkeley gives the following analogy regarding indirect distance perception: one perceives distance indirectly just as one perceives a person's embarrassment indirectly. When looking at an embarrassed person, we infer indirectly that the person is embarrassed by observing the red color on the person's face. We know through experience that a red face tends to signal embarrassment, as we've learned to associate the two. (Wikipedia).

Like most philosophers of the period, Berkeley seems to assume that touch provides immediate access to the world. Visual ideas of an object, on the other hand, vary with one's distance from the object.
As one approaches a tower one judges to be about a mile away, "the appearance alters, and from being obscure, small, and faint, grows clear, large, and vigorous" (NTV §44).
The tower is taken to be of a determinate size and shape, but the visual appearance continually changes. How can that be? Berkeley claims that visual ideas are merely signs of tactile ideas. There is no resemblance between visual and tactile ideas. Their relationship is like that between words and their meanings. If one hears a noun, one thinks of an object it denotes. Similarly, if one sees an object, one thinks of a corresponding idea of touch, which Berkeley deems the secondary (mediate) object of sight. In both cases, there are no necessary connections between the ideas. The associative connection is based on experience (NTV §51; cf. TVV §40, Alciphron, Dialogue 4).

His discussion of magnitude is analogous to his discussion of distance.
Berkeley explores the relationships between the objects of sight and touch by introducing the notions of minimum visibles and tangibles, the smallest points one actually can perceive by sight and touch, points which must be taken to be indivisible. The apparent size of a visible object varies with distance, while the size of the corresponding tangible object is taken to be constant (NTV §55). The apparent size of the visual object, its confusion or distinctness, and its faintness or vigor play roles in judging the size of the tangible object. All things being equal, if it appears large, it is taken to be large. …….. As in the case of distance, there are no necessary connections between the sensory elements of the visual and tangible object. The correlations are only known by consistent experience (NTV §§59, 62-64), and Berkeley argues that measurements (inches, feet, etc.) are applicable only to tangible size (NTV §61)
(Internet Encyclopedia of Philosophy)

Berkeley wrote about the perception of size in addition to that of distance. He is frequently misquoted as believing in size-distance invariance – a view held by the Optic Writers. This idea is that we scale the image size according to distance in a geometrical manner. The error may have become commonplace because the eminent historian and psychologist E. G. Boring perpetuated it. In fact, Berkeley argued that the same cues that evoke distance also evoke size, and that we do not first see size and then calculate distance. It is worth quoting Berkeley's words on this issue (Section 53):

What inclines men to this mistake (beside the humour of making one see by geometry) is, that the same perceptions or ideas which suggest distance, do also suggest magnitude... I say they do not first suggest distance, and then leave it to the judgement to use that as a medium, whereby to collect the magnitude; but they have as close and immediate a connexion with the magnitude as with the distance; and suggest magnitude as independently of distance, as they do distance independently of magnitude.

(Wikipedia)

Before turning to the discussions of Berkeley's idealism and immaterialism, there are several points we should notice. First, there are various points in the New Theory of Vision where Berkeley writes as if ideas of touch are or are of external objects (cf. §§ 46, 64, 77, 78, 82, 88, 99, 117, 155). Since the Berkeley of the Principles and Dialogues contends that all ideas are mind-dependent and all physical objects are composed of ideas, some have questioned whether the position in the New Theory of Vision is consistent with the work that immediately follows. Some scholars suggest that either that the works on vision are scientific works which, as such, make no metaphysical commitments or that allusions to "external objects" are cases of speaking with the vulgar. Secondly, insofar as in his later works Berkeley claims that ordinary objects are composed of ideas, his discussion of the correlation of ideas of sight and touch tends to anticipate his later view by explaining how one "collects" the ideas of distinct senses to form one thing. Finally, the New Theory of Vision includes discussions of the primary/secondary qualities distinction (§§43, 48-49, 61, 109) and of abstraction (NTV §§122-127) that anticipate his later discussions of those topics.
(Internet Encyclopedia of Philosophy)

The question concerning the visibility of space was central to the Renaissance perspective tradition and its reliance on classical optics in the development of pictorial representations of spatial depth. This matter was debated by scholars since the 11th-century Arab polymath and mathematician Alhazen (al-Hasan Ibn al-Haytham) affirmed in experimental contexts the visibility of space. This issue, which was raised in Berkeley's theory of vision, was treated at length in the Phenomenology of Perception of Maurice Merleau-Ponty, in the context of confirming the visual perception of spatial depth (la profondeur), and by way of refuting Berkeley's thesis.
(Wikipedia)

Conclusion:
Berkeley’s empirical theory of vision challenged the then-standard account of distance vision, an account which requires tacit geometrical calculations. His alternative account focuses on visual and tactual objects. Berkeley argues that the visual perception of distance is explained by the correlation of ideas of sight and touch. This associative approach does away with appeals to geometrical calculation while explaining monocular vision and the moon illusion, anomalies that had plagued the geometric account.

The New Theory of Vision

Although Berkeley did not mention his immaterialism in An Essay towards a New Theory of Vision, this work throws important light upon his quarrel with the mathematicians and his rejection of the rationalist point of view. It contains, too, an interesting statement of what Berkeley then thought about geometry. Furthermore, the Essay helps us to see, from what Berkeley said about the objects of vision, how he came to the view that sensible qualities cannot exist "without the mind."

Among the main contentions of the book is the claim that distance or "outness" is not immediately perceived by sight; it is "suggested" in part by the sensations we get in moving our eyes but mainly by association with the ideas of touch. According to Berkeley, we see the distance (and size) of things only in the sense in which we see a man's shame and anger. We see his face, and the expression on it suggests to us how he is feeling. In themselves, shame and anger are invisible. Similarly, we see shapes and colors, which are signs of what we would touch if we were to stretch out our hands, but distance itself is no more seen than anger is. In expounding this view, Berkeley developed the thesis that the objects of sight and touch are utterly disparate, so that no feature of the one can have more than a contingent connection with any feature of the other.

Descartes's theory of the perception of distance
Consideration should first be given to Berkeley's criticisms of an important geometrical account of how distance is perceived and assessed, the account given by René Descartes in his Dioptrics (1637). In this work Descartes referred to six "qualities we perceive in the objects of sight," namely, light, color, shape, distance, magnitude, and situation. Descartes argued that one of the ways in which men ascertain the distance of objects is by means of the angles formed by straight lines running from each of their eyes and converging at the object seen. He illustrated this by reference to a blind man with a stick (the length of which he does not know) held in each hand. When he brings the points of the sticks together at the object, he forms a triangle with one hand at each end of the base, and if he knows how far apart his hands are, and what angles the sticks make with his body, he can, "by a kind of geometry innate in all men" know how far away the object is.
The same geometry would apply, Descartes argued, if the observer's eyes are regarded as ends of the base of a triangle, and straight lines from them are regarded as converging at the object. The more obtuse the base angles formed by the lines running from this base and converging at the object, the farther away the object must be; the more acute these angles, the nearer the object must be.
Berkeley put the matter somewhat differently from Descartes, pointing out that according to the latter's view the more acute the angle formed at the object by the lines converging from the eyes, the farther away it must be; the more obtuse this angle, the nearer the object must be. It is important to notice that this "must" is the "must" of mathematical necessity. From what Descartes said, it is necessarily the case that the more acute this angle is, the farther away the object is; the more obtuse the angle, the nearer the object. "Nearer" and "farther" logically depend upon the obtuseness or acuteness of the angle. In criticizing this view, therefore, Berkeley was criticizing the view that distance is known a priori by the principles of an innate geometry according to which we know that the distance of the object must vary in accordance with the angle made at the object by straight lines converging there from the eyes of the observer.

Berkeley's criticism of Descartes
Against Descartes's view Berkeley brought a complex argument that for purposes of exposition, is here broken up into three parts.
The first is that people who know nothing of the geometry of the matter can nevertheless notice the relative distance of things from them. This is not very convincing, for Descartes obviously thought that the geometry he regarded as "innate in all men" might be employed by them without their having reflected on it.
The second argument used by Berkeley is that the lines and angles referred to by Descartes "have no real existence in nature, being only an hypothesis framed by the mathematicians." This argument is of interest in showing how Berkeley thought that mathematicians were inclined to deal in fictitious entities, but it is unlikely that Descartes was deceived by them in this way.

Berkeley's third and main argument was based upon a theory that he expressed in the words, "distance, of itself and immediately, cannot be seen." William Molyneux, from whose Dioptrics (1692) Berkeley borrowed this theory, had supported it by the argument that since distance is a line or length directed endwise from the object seen to the eye, it can reach the eye at only one point, which must necessarily remain the same however near or far away the object is. If this argument is accepted, then distance could not possibly be seen, and could only be judged or, as Berkeley believed, "suggested."

Distance is suggested by what is seen
What, then, according to Berkeley, is seen? The answer is not altogether clear, but it would seem that he thought that the immediate object of vision is two-dimensional, containing relations of above and below and of one side and the other, with no necessary connection with a third dimension. Hence the relation between what is immediately seen on the one hand and the distance of objects on the other must be contingent and cannot be necessary. Distance, then, must be ascertained by means of something that has only a contingent relationship with what is seen. Berkeley mentioned the sensations we have when we adjust our eyes, the greater confusedness of objects as they come very close to the eyes, and the sensations of strain as we try to see what is very near. But he mainly relied on the associations between what a man has touched and what he now sees. For example, when a man now sees something faint and dim, he may, from past experience, expect that if he approaches and touches it he will find it bright and hard. When he sees something at a distance, he is really seeing certain shapes and colors, which suggest to him what tangible ideas he would have if he were near enough to touch it. Just as one does not hear a man's thoughts, which are suggested by the sounds he makes, so one does not directly see distance, which is suggested by what is seen.

Sight and Touch
Berkeley's view that distance is not immediately perceived by sight is rejected by some writers, for instance by H. H. Price, in his Perception (1932), on the ground that it is plainly contradicted by experience. We just do see visual depth, it is held, so that it is idle to deny this fact on the basis of an argument purporting to prove that we cannot. Again, some critics, such as T. K. Abbott in Sight and Touch (1864) have argued not only that we do get our idea of distance from sight, but also that touch is vague and uninformative by comparison with sight, and hence less effective in giving knowledge of the material world.

As already seen, an extremely important thesis of the Berkeley’s Essay is that the objects of sight and the objects of touch are radically different from one another. We see visible objects and we touch tangible objects, and it is absurd to suppose that we can touch what we see or see what we touch. According to Berkeley, it follows from this that tangible shape and visible shape have no necessary connection with one another.