Perception as a Source of Knowledge AQA A-Level Philosophy

What is direct realism?

* Direct realism is the common sense intuitive view
* we think of physical objects as existing objectively in space and time
* Eg, objects remain the same if you leave a room unless they’re undergoing some sort of physical process like burning
* claims that our senses perceive those physical objects and their properties
* when perceiving the physical object of table, I perceive it’s properties such as colour, shape, size, smell and texture
* Direct realism therefore claims that sense data is veridical – coinciding with reality

What is the perceptual variation issue for direct realism?

* Bertrand Russell argued that what we perceive is not the same as what is in reality and so direct realism is false
* example of a shiny, brown table:
* argues that the colour of the table actually depends on where you stand in relation to it
* light falling on the table making a part of it shiny and therefore white in colour in a certain spot
* if another person were to stand at a different place to you, the white spot would appear differently
* where one person sees the table to be white, another might see it to be brown
* particular spot on an object cannot be two colours at once, therefore colour cannot be a property of the table
* Russell argues this can apply to texture too
* the table at macroscopic level has indentations and grooves
* Shape is also perceptually variable since it depends on the angle

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P1. Our perception of an object can vary without any corresponding change in the object.

C1. Therefore, there is a difference between the properties that physical objects appear to have and the properties they really have.

C2. Therefore, what we perceive and what exists mind-independently are different.

C2. Therefore, the immediate objects of perception and their properties are different to what exists mind-independently.

C3. Therefore, direct realism is false.

How do direct realists respond to the issue of perceptual variation?

They respond by arguing that perceptual variation is the result of perceiving relational properties of mind-independent physical objects

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two types of relational properties:

* relational properties,
* between objects
* properties that objects have in virtue of their relation to other objects
* Perceptual perceptual relational properties
* properties that objects have due to to being perceived
* The property of “looking square” or “looking rectangular”

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* second type of relational property that explains perceptual variation
* since the relation of an object to a perceiver can change, so too can the perceptual relational properties that the object has
* An object could have the relational property of ‘looking rectangular’ while also having the intrinsic property of ‘being square’

How do indirect realists respond to the response made by direct realists in reference to the problem of perceptual variation?

* perceptual relational properties are mind-dependent
* without a mind perceiving them, they would not exist
* relational properties are dependent on minds

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contra direct realism:

* when perceiving relational properties we cannot be perceiving properties “**of”** mind-independent objects or properties that they “**have**”
* Relational properties are properties which an object is only perceived to have
* not properties intrinsic to the object
* properties must be of sense data; mind-dependent representations
* follows that in cases of perceptual variation, a direct realist cannot claim that they are perceiving mind-independent objects and “their” properties
*  direct realism is false

How do direct realists respond to the indirect realist response entailing perceptual rational properties being mind independent (3 points)?

**there are two ways a perceptual relational property can be mind-dependent:**

* Mind dependent due to being a property of sense data
* Mind dependent due to requiring a mind to exist

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* indirect realists are trying to argue that relational properties are mind-dependent in the first way
* direct realists can respond that they are only mind-dependent in the second way
* second way does not conflict with direct realism

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* objects of perception are mind-independent objects and their properties
* we perceive properties of mind-independent objects
* perceptual relational properties may depend on minds
* nonetheless they are still properties that objects **have** due to their relation to a perceiver
* nonetheless they are still properties that objects **have** due to their relation to a perceiver
* It is only from a particular angle that a square object could have the relational property of ‘looking rectangular’
* indirect realists cannot say that the relational properties are mind-dependent in the way of being a property of sense data
* It seems they actually belong to the **objective relation** between a subjective mind and an objective object
* Ultimately, it seems that perceptual relational properties belong both to an object **and** its perceiver

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direct realism can be defended in its claim that perceptual variation can be explained through perceptual relational properties that are properties of mind-dependent objects. A mind-independent object can have relational properties that depend on a mind to exist.

What is the illusion issue for direct realism (1 point)?

P1. During an illusion, I observe an object *p* with property *y*. \n P2. According to direct realism, if I perceive property *y*, then property *y* exists mind-independently. \n P3. During an illusion, there is no property *y*. \n C1. Therefore, our perception of the property *y* of object *p* must be mind-dependent sense data. \n P4. Illusions can be subjectively indistinguishable from veridical perceptions. \n C2. Therefore, in all cases, the objects of perception and their properties are mind-dependent sense data \n C3. Therefore, direct realism is false

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pencil in water example:

* light-refracting properties of water make it look bent
*  illusion occurs when an object (the stick) appears to have a property (of bentness) yet in reality it does not have that property (It isn’t bent)
* perceived illusory property is sense data which exists in the mind, not reality
*  Illusions appear just as real as normal veridical perceptions – they are subjectively indistinguishable

How do direct realists respond to the illusion issue?

* appealing to relational properties
* relational property is one that a thing has by virtue of its relation to something else
* pencil looking bent can be a relational property to a certain observer under certain conditions (ie, through a glass of water)
* observing a stick bent in water does involve observing a mind-independent object and its properties
* therefore direct realism isn’t deemed false by illusions

What is the issue for hallucination?

Hallucination occurs when perceiving an object that doesn’t exist. Therefore, what we perceived must be mind-dependent sense data

P1. During a hallucination I observe an object *p*. \n P2. According to direct realism, if I perceive object *p*, then object *p* exists mind-independently. \n P3. During a hallucination there is no physical object *p*. \n C1. Therefore, the object of perception *p* must be mind-dependent sense data. \n P4. Hallucinations can be subjectively indistinguishable from veridical perception. \n C2. Therefore, in all cases, the objects of perception are mind-dependent sense data. \n C3. Therefore, direct realism is false

How do direct realists respond to the argument for hallucination?

disjunctive theory of perception:

* disjunctive theory of perception shows the possibility that that when hallucinating we are experiencing the product of our imagination
* We experience object p but there is no object p. Direct realists can thereby deny P1 and P2, that when we perceive an object p that there is something that is p
* Therefore this case is disjunctive as it must be *either/or* – it cannot be both – the mind is either connected to reality or separated
* what we perceive is either
* hallucination from our imagination
* a veridical perception of reality
* since they are disjunctive, they cannot be the same
* just because hallucinatory cases are of mind-dependent sense data, it doesn’t follow that all perceptions are mind-dependent sense data too

What is the time lag argument?

* it takes time for light to reach us from an object we perceive
* light from the stars we see in the sky may have taken billions of years to reach earth
* we see those stars as they were billions of years ago, not as they are now
* although the objects of perception we more regularly see are much closer, like a table or chair, the light still takes some time to reach us
* herefore, we are not seeing the objects of perception directly, we are seeing them as they were in the past. Therefore, direct realism is false

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What is indirect realism?

* the view that the objects of perception are a mind-dependent representation which is caused by external mind-independent physical objects
* Sense-data is perceived immediately (directly) whereas physical objects are perceived indirectly
* representation can be different from the object it represents
* The argument from perceptual variation, illusion and hallucination, which try to show that what we see isn’t necessarily the reality, argue for indirect realism

What does Russel define sense data as?

Russell defines sense-data as the ‘content’ of our immediate sensory perception

What is John Locke’s primary/secondary quality distinction?

* objects of perception have primary qualities which are ‘intrinsic’ to the object and secondary qualities which are just in our mind
* Primary qualities are:
* shape
* extension
* number
* movement
* Secondary qualities are:
* colour
* taste
* smell
* touch

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Locke argues for this distinction by pointing to the case of a grain of wheat:

* If you continually divide a grain of wheat, eventually it will become insensible
* having no colour, taste, smell or touch
* However, it will still have a shape, extension, number or movement
* shows that secondary qualities are separable from an object, whereas primary qualities are not

What is the indirect realism issue in relation to scepticism about the existence of mind-independent objects?

* Indirect realism claims that the objects of perception are mind-dependent
* sense data that represents and is caused by mind-independent objects

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* if all we perceive directly are sense-data
* then we never perceive the mind-independent objects which Indirect realists claim are giving rise to and being represented by that sense-data

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* there is a ‘veil of perception’ between our sense data and the external world which we cannot perceive
* therefore, we can’t actually know that mind-independent objects exist at all, let alone whether sense data represents them

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Eg, solipsism could be true; that only my mind exists and my perceptual experience is caused by my imagination

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* first claim of indirect realism
* the objects of perception are mind- dependent sense data
* undermines our ability to justifiably know the second claim
* sense data is caused by and represents mind-independent objects
* direct realism is epistemologically self-defeating and we can never be justified in believing it

What is Russell’s best hypothesis response to the issue of scepticism?

we can neither:

* prove nor disprove either the claim that the external world exists and causes my sense data
* claim that the external world does not exist and so does not cause my sense data

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Since we cannot prove for certain either claim, we are left with making a hypothesis.

Russell argues the question then becomes:

* whether or not the external world exists or does not
* the best hypothesis

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* Cat example:
* you look at a cat in the corner of a room
* you turn away for five minutes
* the cat has moved to a couch
* the cat is independent of the mind, since it moved when it wasn’t being perceived
* therefore, there is an external world which continues existing when unperceived by our minds
* Since this hypothesis actually explains our experience, it is the better explanation and so, Russell concludes it is the best hypothesis

What is the response to Russell’s best hypothesis response to the issue of scepticism?

* wthus no way to say which explanation is better, so Russell’s ‘best hypothesis’ argument fails
* hy is the cat having its own mind-independent existence really a ‘better’ explanation of our experience?
* what criteria is Russell using to judge that?
* makes more sense ‘to us’, but that could just be because of our habit of thinking that there is an external world.
* if we discount that, it’s hard to see what possible reason we could have to prefer Russell’s explanation to the explanation of solipsism
* both explanations are equally consistent with any and all experience
* no justification to prefer either
* thus no way to say which explanation is better, so Russell’s ‘best hypothesis’ argument fails

What is solipsism?

the sceptical view that only our mind exists and the physical world does not

What is John Locke’s argument from the involuntary nature of our experience?

* argues that perceptions from sense experience have a key difference to perceptions from memory or imagination
* we have no choice over what we perceive in sense-data
* we can choose what to remember or imagine
* if there really were no external world causing our sense-data, then everything must be in our mind
* we should expect to have choice over perceptions from sense experience
* however we do not – if we look at a bottle of water we have no choice but to see one
* yet if we want to imagine a bottle of water filled with gold or remember the last time we drank from one, we can
* Since we have choice over perceptions which originate from our mind, but have no choice from those from sense experience:
* sense experience does not originate from our mind but from an external world

What is the argument from coherence of various kinds of experience (Locke and Cockburne)?

Locke also argues that sense-data from different senses back each other up:

* eg, an apple
* I can touch it to see if it also feels like one
* taste it to see if it also tastes like one

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Locke combines these two arguments in the example of changing how paper looks by writing on it:

* sight and the sense of your hand moving cohere
* you cannot cause the words to appear on the paper by mere imagination
* once it is written, it cannot be changed except by further writing
* if someone else read out what you had written, there would be coherence between your auditory (hearing) sense-data

Lock argues this ‘leaves little reason for doubt’ that there is an external world

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**Catherine Cockburn** also responds to scepticism about the existence of mind-independent objects with an argument from experiential coherence

* first points to the radical difference between experiences gained from different senses
* the sound a waterfall makes is not just different to but of a very different sort than the visual experience of it
* we learn to pair visual and auditory experiences together
* we are able to make an inference from one to the other
* we can infer and accurately *predict* what it looks like; and vice versa


* The fact that we can accurately infer and predict our experiences suggests that there is some mind-independent object which both senses perceive yet is independent of any particular sense

What are the responses to the argument from the coherence of various kinds of experience (Locke & Cockburne)?

* **Locke hasn’t** ***proven*** that there is an external world of physical objects, he has merely given some reasons as to how it *makes sense of our sense-data for there to be one*
* assumes all parts of our mind are under our control
* might be some reason unknown to us why sense-data originating from our mind isn’t under our control
* might also be some reason why we get the same information from different senses, despite them also potentially originating from our mind

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* **indirect realism can still be justified** by Locke’s arguments if we use Russell’s notion that it is the best hypothesis
* The existence of the external world is the best explanation of lack of choice over perceptions and the coherence of various senses

What is the argument from Berkeley that we cannot know the nature of mind-independent objects because mind-dependent objects cannot be like mind-independent objects?

indirect realism relies on the claim that our perceptions are mind-dependent sense data which represents mind-independent objects

* Berkeley attacks this claim with the likeness principle:
* that to justifiably say that two things to be alike, they must be comparable
* ideas (mind-dependent) can only be compared to other ideas
* no way to compare ideas to mind-independent objects
* so resemblance between them cannot be justifiably claimed
* this issue attacks the claim of indirect realism that the objects of perception represent mind-independent objects

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How does an indirect realist respond to Berkeley’s use of the likeness principle?

* Berkeley assumes that representation requires resemblance
* there are other methods of representation
* eg, the symbols we use in language are completely arbitrary
* they have no resemblance to the objects they refer to
* the word ‘chair’ does not resemble a chair but nonetheless can represent it
* mind-dependent objects can be ‘like’ mind-independent objects if we take ‘like’ to involve representation without resemblance

How can Berkeley’s argument be defended from the indirect realist response to his use of the likeness principle?

**we could defend Berkeley by taking** his argument to not be attacking whether an idea *could* be like a mind-independent object, but whether we could ever be in a position to *know* that it does

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Berkeley seems to be saying that:

* in order for a person to know that an idea is like a mind-independent object, they would have to compare them
* that cannot be done since we have no direct perception of mind-independent objects
* no one can justifiably claim that ideas represent mind-independent objects
* therefore indirect realism cannot be justified

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Even if we restrict ‘likeness’ to representation, our perceptions might not even represent the mind-independent world, and could be totally unlike our perceptions in any respect

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we just cannot know whether our perceptions represent mind-independent objects

Indirect realism leads to this sceptical issue

What is idealism?

claims we perceive ideas directly as they are because to be is to be perceived

What is idealism’s issue of illusions?

* when we perceive an object like a stick in water appearing bent that it really is bent


* If we reach into the glass to feel that the stick is straight, while also looking at the stick appearing bent, then we perceive two inconstant properties at the same time
* cannot be the case that the stick is both bent and straight
* At most one of those properties can be the reality and the other must therefore be an appearance, i.e., sense data
* follows that there is a distinction between appearance and reality
* so, it is not the case that to be is to be perceived and therefore Berkeley’s Idealism is false.

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idealism fails in its claim that to be is to be perceived, which means it is not the case that the objects of perception are mind-dependent ideas

How does Berkeley respond to idealism’s issue of illusions?

this is a mistake in the language we use to talk about the situation

* when we say ‘the stick is bent’ what Berkeley argues we really mean is that it would look bent under normal conditions, clearly false


* Berkeley suggests instead saying “the stick looks bent”, which is clearly true
* An indirect realist would want to insist that although the stick ‘looks’ bent, it isn’t ‘really’ bent

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this argument however, presupposes a distinction between appearance and reality, which Berkeley has already denied in his attack on the primary/secondary quality distinction

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Illusion is only a problem for a theory if it claims that the stick looks bent but is really straight

For Berkeley:

* there is no way a thing “really is” aside from how it is perceived.
* It’s not that he denies that it is “really” straight, it’s that he denies there is any way the stick “really is” aside from how it “looks”; how it is perceived.

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Berkeley denies the inference from the stick looking bent to the claim that the stick really is straight

* confusion over what Berkeley meant by ‘to be is to be perceived


* to be bent is merely to look bent, not to possess a quality of bentness

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The argument from illusion against idealism begs the question by assuming that there is a distinction between appearance and reality

What is idealism and the issue of hallucination?

* a hallucination is the perception of an object which doesn’t exist.
* the possibility of hallucinations pose a problem for idealism because they are subjectively indistinguishable from veridical perceptions
* for Berkeley, a veridical perception is when we perceive an idea that is in the mind of God
* yet hallucinations according to Berkeley come from our imagination, not from God’s mind
* the imagination normally produces voluntary and relatively dim perceptions which are not vivid
* Berkeley argues that at times it can produce involuntary and vivid perceptions

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The problem is:

if some perceptions are hallucinations from our imagination and they are subjectively indistinguishable from other perceptions, then we can’t tell the difference between hallucination and reality (reality being an idea in the mind of God)

Berkeley has an epistemological issue:

* an issue with scepticism
* problem for Berkeley as he claimed that defeating scepticism was a reason to accept his theory over indirect realism

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How does Berkeley respond to idealism’s issue of hallucination and why does it fail?

**Berkeley responds** that hallucinations lack logical connection to the rest of our experience

**However, this response is unsuccessful because**:

* hallucinations might be logically connected to the rest of our experience however
* someone with a fever might look out a window and hallucinate a person walking down the street
* there is nothing illogical about that and so no way to tell

What is idealism’s issue of solipsism?

Berkeley’s arguments for Idealism conclude that the the objects of perception are mind dependent ideas

* When we perceive a mountain or a tree, they have no mind-independent existence as they are just ideas in my mind
* The problem is that it’s difficult to see how this would not apply to other people too
* follows that other people are therefore just ideas in my mind

**this issue** does not suggest that Idealism is false

* it only shows that Idealism leads to this sceptical issue
* somewhat undermines Berkeley’s claim that his theory is superior to the realist theories because it solves issues of epistemological scepticism

**However:**

* Berkeley thinks that Idealism provides an argument for God’s existence which would show that solipsism is false since God also exists, not just my mind

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How does Berkeley respond to idealism’s issue with solipsism?

Berkeley argues that God must exist because our ideas must exist in God when not perceived by us

* the complexity and regularity of the ideas we perceive shows that they come from God’s mind
* Idealism faces the issue of explaining the regularity of our perceptions
* this includes their apparent continued existence when unperceived

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If I throw a lit match into an empty room, leave it and come back later, the room will have changed

According to Berkeley however, ‘to be is to be perceived’:

* Since the room is unperceived it does not exist, yet Idealism is then left with the problem of explaining how it could have undergone change.
* Berkeley solves this problem by claiming that God perceives the room and indeed everything other idea, thereby keeping them in existence regardless of whether any human is observing them.

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**In the Principles,** Berkeley argues that once Idealism is established to be true, an argument for God follows as the required causal explanation of our ideas.

If Idealism is true, our ideas cannot be caused by mind-independent objects

the only other options are that they are caused by:

* other ideas
* our own minds
* another mind.

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Ideas are:

* perceived to be passive
* to have no causal power
* since to be is to be perceived
* ideas have no causal power.

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I can cause some ideas through imagination, but others are involuntary and therefore cannot come from my mind, so the third option must be true

The involuntary ideas we experience must come from another mind

Berkeley argues that the immeasurable complexity and regularity of the ideas we experience shows that this other mind must be far greater than our own, i.e., God.

This alone counters Solipsism since if God’s mind exists then my mind is not the only mind

However, Berkeley also argues we at least have some evidence to justify thinking other people have minds too. We can infer that on the basis of our own experience of them.

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What is the consequence if **Berkeley’s attack** on the primary/secondary quality distinction and master argument fail to establish idealism/if some other argument proves idealism false?

his inference of God would likewise fail

Berkeley’s defence against solipsism relies on his proof of God:, which relies on his arguments for idealism

it’s only if Idealism is true that God’s existence is required to explain the regularity of our perceptions and that therefore my mind is not the only one which exists

### **Whether God can be used to play the role that he does in Berkeley’s idealism**

* **In Berkeley’s Idealism,** God plays the role of perceiving all ideas and causing our ideas
*  this involves those ideas being in God’s mind
* this leads to an issue

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* The idea that God could have the same ideas as us is problematic for the traditional view of God
* God could experience pain, for example
* God cannot suffer
* God’s ideas are eternal yet ours are transient
* God also has ideas of all possible objects, not just the ones that we experience

it cannot be the case that our ideas originate from God’s mind

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Berkeley is therefore left with the sceptical issues of solipsism and accounting for the origin and regularity of our ideas, including their changing when unperceived