Perception as a Source for Knowledge

Question 1

Direct realism

Answer 1

Direct realism makes two claims:
1. There is a real mind independent world ‘out there’ [hence the use of the word realism] containing objects with physical properties.
2. Our senses directly perceive these objects and their physical properties.
The direct realist would claim that I use my senses to directly perceive the properties of the desk.
I see its shape and colour; I can smell it; I can feel its texture; I could even taste it.
The ‘immediate object’ of my perception (the content of my perception) is the desk itself and its properties.
What perception gives us is a direct awareness of mind-independent objects.

Question 2

Direct realism: challenge 1 perceptual variation - Russel

Answer 2

P1: There are variations in the perception of an object.
P2: Although our perception of an object changes, there isn’t a corresponding change in the physical object.
C1: Therefore, the properties that physical objects have and the properties they appear to have are not identical.
C2: Therefore, what we are immediately aware of in perception is not exactly the same as what exists independently of our minds.
C3: Therefore, we do not perceive objects directly.
Russell claims that the immediate objects of our perception are ‘sense-data’ (our perceptions), which are quite different from the object itself.
Sense-data varies; the object remains the same.

Question 3

Direct realism response 1 to perceptual variation

Answer 3

Response 1:
Despite what Russell says, it is possible to say that some of the colours of the table are more real than others.
We could, for instance, say that the real colour of the desk is that which is perceived by normal observers in normal conditions. The fact that we don’t always see it this way does not mean that direct realism is false.
This works much better when we think of shape and size.
If we were to all measure the desk we would find it had the same dimensions. And our observations can be tested against reality. We would soon realise that our perceptions of the size and shape of the table were incorrect if we tried to force it through a circular door that was too small.

Question 4

Direct realism: does response 1 to perceptual variation work

Answer 4

No.
It is impossible to define what normal conditions are, let alone who are the normal observers!
What makes a condition normal?
What makes an observer normal?
No.
Even if we could establish what normal conditions are, the perception of the object would still constantly change.
This means that we are still perceiving sense data.
The immediate objects of perceptions would be sense data and not the objects themselves.
This would still mean that direct realism is false.

Question 5

Direct realism response 2 to perceptual variation

Answer 5

Perhaps there is more than one type of property that an object can have.
Mind independent properties exist even when nobody is perceiving the object.
Relational properties are properties of the object that it has only in relation to your mind, e.g. it’s changing shape and colour as you move around it.
A relational property is a property that something has in relation to something else.
E.g. ‘being north of’ is a relational property.
Russell is wrong to claim that because our perception of the table changes, the immediate object of perception is sense-data and not the properties of the object itself. When our perception of the table changes, we are still experiencing the table’s properties. It’s just that some of these are mind independent and some are are relational properties!
Both types of property can exist alongside one another
If direct realism claims that the immediate objects of perception are mind-independent objects and their properties, then direct realism may not be vulnerable to the perceptual variation criticism after all. Mind-independent objects have relational and non-relational properties, both of which are the immediate objects of perception.

Question 6

Direct realism does response 2 to perceptual variation work

Answer 6

This response misses the point.
Relational properties are mind-dependent.
This means that they can only be sense data.
Which means that we do not perceive the mind-independent object as it is.
It is a mistake to think of relational properties like non-relational properties.
Because they are mind-dependent, they vary from person to person and must be nothing other than sense data.

Question 7

Direct realism: challenge 2 - the argument from illusion

Answer 7

First Part
P1: Illusions are indistinguishable from true (veridical) perception. E.g., the pencil in water really does look bent.
P2: Yet we know that illusions are false. We know, for example, that the mind-independent pencil is straight.
C1: Therefore, in illusions, the immediate object of perception must be sense data, not the mind-independent object itself and its properties.
P3: If the immediate objects of perception in illusions are sense data, then the immediate objects of perception are not necessarily mind-independent objects and their properties in all cases.
C2: Therefore, direct realism is false.

Question 8

Direct realism argument from illusion response

Answer 8

An illusion isn’t a fair test - not normal conditions
The problem with this response is what is the definition of normal conditions. Illusions are an artificial situation, that we don’t normally see things in this perspective.

Question 9

Direct realism: challenge 3 - the argument from hallucination

Answer 9

P1: Hallucinations are indistinguishable from true perception. E.g., it really looks like there is a lobster on my desk.
P2: Yet we know that hallucinations are false. There is no lobster on my desk.
C1: The mind-independent world is not causing the perception of the lobster.
C2: Therefore, the immediate object of my perception (the lobster) must be mental - it must be sense data.
P3: If the immediate objects of hallucinations are sense data and not mind-independent objects and their properties, then the immediate objects of perception are not necessarily mind-independent objects and their properties in all cases.
C3: Therefore, direct realism is false.

Question 10

Direct realism argument from hallucination responses

Answer 10

Response 1:
We can in fact know when we’re hallucinating. How else would be able to tell the difference between a hallucination and a veridical (true) perception?
[If we couldn’t tell the difference between a hallucination and a veridical experience, the challenge wouldn’t exist in the first place!]
Response 2:
Hallucinations shouldn’t be thought of as perceptions.
Even if it is impossible to tell the difference between hallucinations and true perception, this does not mean that they are not very different things.
If hallucination and perception are very different things then we can’t use hallucinations to challenge a theory of perception.

Question 11

Direct realism: challenge 4 - the time lag argument

Answer 11

It takes time for light to reach our eyes. When we look at the stars, we are viewing events that happened thousands of years ago. We are, quite literally, looking at the past.
P1: When we perceive an object, direct realism claims that the immediate object of perception is the mind-independent object and its properties. We do not experience mere sense-data.
P2: Because of time lag, when we see an object we are viewing it as it was (i.e., in the past).
C1: Therefore, we do not experience the mind-independent object and its properties as it is; we experience it as it was.
C2: Therefore, direct realism is false.

Question 12

Direct realism the time lag argument response

Answer 12

The time lag argument does not mean that we don’t perceive the object directly. It’s just that we see it as it was a few moments ago (or more if we are talking about astronomical phenomena).
The time lag argument confuses what we perceive with how we perceive.
Yes, we do have visual perception via light waves, but this doesn’t mean that we are not seeing a mind independent object. Light waves are simply part of the story of how we see physical objects.

Question 13

Indirect realism

Answer 13

The view that:
- The external world exists independently of the mind (hence, realism)
- But we perceive the external world indirectly, via sense data (hence, indirect)
Indirect realism says the immediate object of perception is sense data. This sense data is caused by, and represents, the mind-independent external world.
Indirect realists believe that a real mind-independent world exists, and that we perceive it indirectly.
Unlike direct realists, indirect realists claim that we perceive sense-data, or a representation of the mind-independent world.

Question 14

Sense data

Answer 14

Sense data can be described as the content of perceptual experience.
It’s not a physical thing, it exists in the mind. However, sense data is said to be caused by and represent mind-independent physical objects (see diagram above).
Sense data is private. No one else can experience your sense data.
This avoids the problems with direct realism described above. For example, differences in perceptual variation can be explained by differences in sense data. The object itself stays the same throughout even if the sense data changes.

Question 15

Indirect realism Lockes - two qualities

Answer 15

Primary qualities: these are the qualities that an object has ‘in itself’.
- They exist in the object itself and are therefore independent of the mind.
- They exist when the object is not being perceived.
- They are accessible by more than one sense.
- They are quantifiable, i.e. they can be expressed in numerical terms.
- Locke’s examples are extension (size), shape, motion, number, solidity.
Secondary qualities: these are the qualities that give rise to sensations in us.
- They are relational, i.e. they are only experienced in the interaction between the mind and the object.
- They are mind dependent.
- They may differ from person to person.
- They are caused by primary qualities.
- Each secondary quality is accessible by only one sense.
- They are not quantifiable.
- Locke’s examples are colours, sounds, tastes, smells and temperature.
According to Locke, the secondary qualities that we experience do not resemble the objects themselves, e.g. a red cricket ball is not actually red in itself.
According to Locke, the primary qualities that we experience do resemble the objects themselves, e.g. the roundness of the cricket ball is a quality that the ball has in itself, even when there is nobody to perceive it.

Question 16

Indirect realism: Issue 1 - scepticism about the nature of mind-independent objects

Answer 16

If all that I directly perceive is a representation of reality in my mind (sense data), then I can never perceive objects outside of my mind.
How can I determine if my perception (world 2) resembles the world as it is (world 1)?
In order to judge the similarity between the two worlds, we would need to ‘step outside’ of our perception and adopt a ‘God’s-eye view’. This is impossible because we are always perceiving the world through our senses!
The veil of perception:
Another way of understanding this is to imagine that there is a veil in front of you that conceals the ‘real’ mind-independent world.
Let’s just imagine that the veil is always there in front of you. (You can never step around it.)
And because the veil is permanently there, you have no idea if what you are seeing is what the world is really like.

Question 17

Indirect realism: Issue 1 - scepticism about the nature of mind-independent objects responses

Answer 17

1. Locke believes that our sensations of primary qualities do resemble the objects; it’s just the secondary qualities that don’t. This means that we do know something about the nature of the mind-independent world.
   [But surely the veil of perception problem suggests that we can’t make this claim about our perception of the primary qualities.]
2. But if everybody sees the world in the same way (e.g., we all see that cricket balls are red and round) then it’s highly likely that the they really are red and round.
   [The fact that we all see the cricket ball this way doesn’t mean that it is really like this. We are all viewing the world from behind the veil of perception.]
3. Perhaps the fact that primary qualities are amenable to mathematical description (they can be quantified) makes them more likely to resemble the object.
   [But why should amenability to mathematical description make the primary quality more objective?]
4. Perhaps because our senses are finely tuned to help us survive (think evolution), our perception must strongly resemble the world.
   [Survival is not necessarily the same thing as seeing the world as it really is].

Question 18

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects

Answer 18

IF WE CAN’T BE SURE THAT WHAT WE PERCEIVE RESEMBLES THE MIND-INDEPENDENT WORLD, THEN HOW CAN BE SURE THAT SUCH A WORLD EVEN EXISTS?!
This question is of the greatest importance. For if we cannot be sure of the independent existence of objects, we cannot be sure of the independent existence of other people’s bodies, and therefore still less of other people’s minds, since we have no grounds for believing in their minds except such as are derived from observing their bodies. Thus if we cannot be sure of the independent existence of objects, we shall be left alone in a desert—it may be that the whole outer world is nothing but a dream, and that we alone exist.

Question 19

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects common response

Answer 19

Common sense response: Consider what other people say. For example, if we are all sat around a table, surely we can agree that we are perceiving a table that exists independently of us. You see it, I see it…

Question 20

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects response 1

Answer 20

Response 1: The best hypothesis (Bertrand Russell)
P1: Either mind-independent objects exist and cause my sense data or mind-independent objects do not exist and do not cause my sense-data.
P2: I can’t prove either claim is true or false.
C1: Therefore, I have to treat them as hypotheses (proposals that need to be confirmed or rejected by reasoning or experience).
P3: the proposal that mind-independent objects exist and cause my sense-data is better.*
C2: Therefore, mind-independent objects exist and cause my sense-data.
For a hypothesis to be better it must be able to provide an explanation for experience.
If Russell sees a cat in a corner of his room and then later on his sofa, he has had two distinct experiences.
There are two ways of explaining this:
a) The mind-independent cat moved from the corner of the room to the sofa.
b) There is no mind-independent cat; there are just two distinct experiences of a cat.
Explanation a) is superior because explanation b) doesn’t explain anything at all!

Question 21

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects response 2

Answer 21

Response 2: The involuntary nature of experience (Locke)
P1: In memory and imagination, I am able to choose what I experience.
P2: In perception, I am unable to choose what I experience.
C1: Therefore, the source of memory and imagination is different from the source of perception.
P3: The source of my memory and imagination lies within my mind.
C2: Therefore, the source of my perception must lie outside of my mind.
C3: Therefore, mind-independent objects are the source of my perception.
C4: Therefore, mind independent objects exist.

Question 22

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects does response 2 work

Answer 22

Does C1 follow? Why must their sources be different?
In addition to this, we can think of dreams. In dreams we have a perception that we have no control over. Except in rare cases, we cannot choose the content of our dreams. And yet we all acknowledge that dreams come from within us.
The issue of whether we can control our perceptions has no relation to the issue of where they come from.

Question 23

Indirect realism: Issue 2 - scepticism about the EXISTENCE of mind-independent objects response 3

Answer 23

Response 3: Coherence of various kinds of experience (Locke)
Locke: Different senses confirm the information that each supplies, e.g. if I see a fire and doubt that it is real I can touch it to check. The fact that both senses cohere with one another is evidence that they are pointing to the same mind-independent reality.
When I see the fire and feel the heat from it, my senses cohere with one another. This suggests that there really is a mind-independent fire.
The fact that we have such sophisticated and consistent associations between the different sensations can only be explained by the fact that they refer to objects that exist independently of the mind. The objects exist in a mind-independent universe that behaves in a law-like manner.

Question 24

Indirect realism: Issue 3 - Berkeley: we cannot know the nature of mind independent objects. First Objection

Answer 24

P1: Locke claimed that we can, more or less, determine an object’s primary qualities through our sense experience. E.g. We can see its shape and size.
P2: Our observations of the primary qualities of an object do not remain constant. E.g. a coin looks oval when looked from an angle, circular when looked at from above. Our sense-data varies. [remember perceptual variation]
P3: The primary qualities of objects are the qualities that an object has ‘in itself’ and are meant to remain constant.
C1: Therefore, our sense-data, which varies all the time, cannot tell us about the primary qualities of objects.
C2: Therefore, if we accept Locke’s indirect realism, we cannot know the nature of mind-independent objects.

Question 25

Indirect realism: Issue 3 - Berkeley: we cannot know the nature of mind independent objects. Second objection

Answer 25

P1: You can’t say that two things resemble each other unless you can compare them. P2: To compare our sense-data with the object it represents and say it resembles it, you would need to see the object directly. P3: According to indirect realism, we can’t see the object directly. C1: Therefore, if we accept indirect realism we can’t make a comparison between our sense-data and the object it is said to represent. C2: Therefore, if we accept indirect realism we can’t say that our sense-data resembles the mind-independent object C3: Therefore, if we accept indirect realism, we cannot know the nature of mind-independent objects.

Question 26

Indirect realist response to issue 3

Answer 26

It seems that the indirect realist can only respond by saying that sense-data does not actually resemble the objects in themselves. They just represent them.

Question 27

Idealism

Answer 27

The view that: - There is no external world independent of minds (so it rejects realism – both direct and indirect) - We perceive ideas directly. In other words, the immediate objects of perception are mind-dependent ideas. Unlike direct realism and indirect realism, idealism says there is no mind-independent external world. Instead, idealism claims that all that exists are ideas. Idealism says that unless something is being perceived, it doesn’t exist.

Question 28

Berkeley’s attack on the primary/secondary distinction Part 1

Answer 28

His first argument consists of two parts: 1) He argues (like Locke) that secondary properties are mind-dependent. 2) He goes on to argue (unlike Locke!) that primary properties are also mind-dependent. Part 1 - Secondary properties are mind-dependent: P1: A cloud from a distance looks pink, but up close it loses its colour (or appears grey). P2: A solid physical object, viewed through a microscope, appears to have different colours than those it has when viewed normally. P3: Different animals perceive the colours of objects differently. P4: If colours really existed in physical objects, then to change the colour, it would be necessary to change the object itself. But, of course, different kinds of light - daylight, candlelight, etc. - change the colour of an object without changing the object. C1: Therefore, all colours are appearances, not properties of physical objects.

Question 29

Berkeley’s attack on the primary/secondary distinction Part 2

Answer 29

Part 2 - Primary properties are also mind-dependent: P1: What looks small to me may look huge to a small animal. P2: What looks small from a distance looks large when viewed close up. P3: What looks smooth to the naked eye appears craggy and uneven under a microscope. P4: If you look at a circle straight on, it looks circular. But if I’m looking at it from an angle, it looks elliptical. We see it differently, but it doesn’t change. P5: Even motion isn’t constant. We measure the speed of motion by how quickly our minds work - to a creature that responds much faster than us, e.g. a housefly, our fastest movements appear leisurely. P6: In the case of colour, when an object appears to have many colours, depending on how it is perceived, we can’t say that it has one real colour which is independent of how we perceive it. C1: Therefore, (from P1 to P5) we can’t say that an object has one real shape, size or motion, independent of how it is perceived. C2: Therefore, the primary qualities of objects are just as mind-dependent as secondary qualities.

Question 30

More reasons to question the primary/secondary distinction - the likeness principle

Answer 30

P1: A sense experience can only resemble (be like) another sense experience (e.g. colour can only resemble colour). C1: Therefore, it is not possible to claim that sense experiences resemble things that are not sense experiences. ‘How can that which is sensible be like that which is insensible?’ (Berkeley). C2: Therefore, we cannot say that our sense experiences resemble the primary properties of mind independent objects. C3: Therefore, we cannot hold on to the claim that there are mind-independent objects with primary properties that are perceived indirectly through the senses. However, can we question P1? If so, this doesn’t rule out the possibility that sense experiences may resemble (in some way) the primary qualities of a mind -independent object.

Question 31

Berkeley's Master Argument to establish idealism

Answer 31

Berkeley asks us to conceive of a tree that exists independently of our minds. This might seem straightforward. However, Berkeley says this is not the case. He says that the tree you imagined was in your mind. And if it is in your mind it is not the idea of a tree that is independent of your mind. Since any thought of an object outside of one’s mind can only take place in one’s mind, the idea of a mind-independent object is contradictory. P1: It is impossible to conceive of a mind-independent object without using one’s mind. P2: If the thought of an object exists in the mind, the object cannot exist outside of the mind. C1: Therefore, it is impossible to really imagine an object that exists outside of one’s mind. It is impossible to conceive of a mind-independent object. (unjustified claim in P2 as the problem)

Question 32

Issues with Berkeley's idealism: Illusions, hallucinations and dreams.

Answer 32

Unlike indirect realism, idealism provides no means by which we can distinguish between veridical (true) perception and our sense perception. This is because there is no distinction made between our perception and the ‘real’ mind-independent world. The ‘real’ world is the collections of ideas in our perception. Illusions: idealism commits us to believing that because the pencil in the water appears to be bent, it is indeed bent: to exist is to be perceived. Reality is perception. Dreams: idealism commits us to believing that what we experience in the form of dreams is exactly the same as reality: to exist is to be perceived. Reality is perception Hallucinations: idealism commits us to believing that what we experience in hallucinations is exactly the same as reality: to exist is to be perceived. Reality is perception

Question 33

Berkeleys response to Issues with Berkeley's idealism: Illusions, hallucinations and dreams.

Answer 33

We can in many cases, make a distinction between veridical and imagination without reference to an external world because: 1) Veridical perceptions are more distinct and less faint than imagination. (Think of the difference between a dream experience and veridical experience). 2) In many cases we can control what we imagine; we can’t necessarily do the same with veridical perception. 3) Illusions, hallucinations and dreams do not concur with our overarching regularity of experience. (E.g. If I dreamt I was floating in space in my car and talking to aliens, this would not concur with the regularity of my typical experience. I would be able to know that this wasn’t veridical.) 4) And in illusions, the mistake occurs when we make the false inference that because the pencil appears bent, it won’t feel bent, or look bent when it is out of the water.

Question 34

Issues with Berkeley's idealism: Solipsism

Answer 34

Solipsism: The view that all that can be known to exist is my own mind. Idealism says that we cannot know anything beyond our experience. We can only know the contents of our minds. The master argument in particular claims that this is the case: if it is impossible to conceive anything beyond my own mind, then only my mind can be known to exist. This leads us directly to the philosophically unacceptable position of solipsism. (It is philosophically unacceptable because it is an embrace of the most extreme form of scepticism. It says we can never know anything about the external world.)

Question 35

Issues with Berkeley's idealism: The ‘gappiness’ of objects

Answer 35

If to exist is to be perceived, then what happens we are not perceiving something. Surely, idealism would have to claim that the object of perception stood existing when it is not being perceived. (Does the tree stop existing when we are not perceiving it?)

Question 36

Issues with Berkeley's idealism: The regularity of the universe

Answer 36

Why does the universe behave in a regular and ordered way? If we believe in physical matter beyond our experience then we could say that this follows regular laws independently of our minds. However, idealism doesn’t allow for a physical material world beyond our perception. It cannot, therefore, explain the regularity of the universe.

Question 37

Berkeleys response to solipsism, the regularity of experience and gappiness

Answer 37

The fact that I have no control over my experience suggests that solipsism isn’t correct. In addition, the regularity and predictability of experience suggests the involvement of a powerful and good intelligence. Sense data are, therefore, originally in the mind of God and he produces them in me in a manner that makes them regular and predictable. God permanently perceives things and so the gappiness problem is overcome!

Question 38

Problems with the role played by God - problem 1

Answer 38

Problem 1 The use of God to shore up a philosophical point is often regarded as a sign that there is something seriously wrong with the position! It seems that God is brought in by Berkeley as a way of responding to the problems that face idealism. Without independent reasons a) to suppose that God exists and b) to suppose he performs the role that Berkeley says he does, then the introduction of God isn’t really an explanation of anything! (We could simply solve all philosophical problems by saying that they are all part of God’s mystery.)

Question 39

Problems with the role played by God - problem 2

Answer 39

If we are unable to conceive of anything that exists independently of the mind (remember the master argument), then it would appear that we are unable to make any claims about an independently existing God!

Question 40

Berkeleys response to the problems with the role played by God

Answer 40

We can infer the existence of God through the regularity of our sense experience. He uses the analogy of language: we can infer the existence of other minds and thoughts by listening to the language that people use. Upon listening to a complex sentence, it would not be unreasonable to suppose that there was a mind and thoughts that are responsible for it. We would suppose that there was an intelligence at work. In the same way, the regularity of experience acts like a complex language and indicates an intelligence beyond it. God speaks to us through our senses. In addition to this, and directly targeted at problem 2, we can have the idea of other minds (including God’s) through analogy with our own mind. We know we have a mind and so can infer that other minds, including God’s, exist. Rather than using God to save his theory, Berkeley believes that his theory is actually a demonstration of God’s existence.

Question 41

Problems with the role played by God - an imperfect God

Answer 41

P1: If our sensations exist in God’s mind, he must experience every sensation that we experience. P2: We experience pain and discomfort. C1: Therefore, God must experience pain and discomfort. P3: As a perfect being, God cannot experience pain and discomfort. C2: Therefore, there is a contradiction involved in saying that God produces our experience and that he is a perfect being.

Question 42

Berkeley's response to the problems with the role played by God - an imperfect God

Answer 42

The way that we experience sensations is very different than the way they are in the mind of God. When we experience pain, we experience it against our will and according to the regular laws that God has made. These laws are systematically connected to the way our (perceived) bodies are. In other words, there is a regular God given law that determines how we experience pain. But God doesn’t experience sensations against his will and neither does he have a body that determines what his experience should be like. God is, therefore, aware of what the sensations are like, even though he himself doesn’t suffer from them.