Perception as a source of knowledge
Direct realism
Direct realism claims that the immediate object of perception is the physical object itself. We don’t perceive it in virtue of perceiving something else that ‘mediates’ between our minds and the physical object.
There is an external world/ objects in the world cause our sense perceptions
We learn of the world through our senses
Things are exactly as they appear
This is considered to be the common sense or instinctual belief of most people and off-duty philosophers
Direct realism claims that the immediate object of perception is the physical object itself. We don’t perceive it in virtue of perceiving something else that ‘mediates’ between our minds and the physical object.
There is an external world/ objects in the world cause our sense perceptions
We learn of the world through our senses
Things are exactly as they appear
This is considered to be the common sense or instinctual belief of most people and off-duty philosophers
Issues with direct realism
The argument from illusion - When we look at the stick half-submerged in water, we see a bent stick. But the stick isn’t bent. So what is? We see something bent, but it isn’t the stick. So it must be a sense-datum.
We have a mental image of a bent stick; the stick in the image is bent. But that means that we don’t see the real stick directly; we see it indirectly, via sense-data. So direct realism is false, and representative realism must be right.
We must admit that in cases of illusion, we do not see the object as it is. The stick isn’t really bent. So the object doesn’t have the property that it appears to have.
First Premise. Suppose we are perceiving a straight stick SS half submerged in water.
Second Premise. In perceiving SS, we are immediately aware of something B which is bent. 13
Third Premise. B cannot be identical to SS because SS is straight while B is bent.
Conclusion. Direct Realism is false. We do not directly perceive SS; we are aware of SS only by means of a prior awareness of B.
The argument from perceptual variation (Russell’s table argument) - Russell put forward an argument that can be used against direct realism which drew attention to the table he was sitting at when he was writing about it
Russell was an empiricist so did believe that we get knowledge from our senses but he thought that our senses are prone to mistakes.
If the table looks and feels different from different angles, or from the same angle when perceived by different people, how can we be directly perceiving the table. There must be something happening between object and eye and mind.
Indirect realism
Indirect realism claims that we perceive physical objects which are mind-independent, but we do so via, or in virtue of, perceiving mind-dependent sense-data that are caused by and represent physical objects. We perceive sense-data immediately, and physical objects indirectly.
Sense data are mental images which we see exactly as they are but the represent physical objects in various ways (not always exactly as they are). Sense-data only exist while they are being perceived but the object itself can exist when it is not being perceived. Sense-data are private, physical objects are public.
An idea closely related to sense data is John Locke's distinction between primary and secondary qualities:
The argument from illusion - When we look at the stick half-submerged in water, we see a bent stick. But the stick isn’t bent. So what is? We see something bent, but it isn’t the stick. So it must be a sense-datum.
We have a mental image of a bent stick; the stick in the image is bent. But that means that we don’t see the real stick directly; we see it indirectly, via sense-data. So direct realism is false, and representative realism must be right.
We must admit that in cases of illusion, we do not see the object as it is. The stick isn’t really bent. So the object doesn’t have the property that it appears to have.
First Premise. Suppose we are perceiving a straight stick SS half submerged in water.
Second Premise. In perceiving SS, we are immediately aware of something B which is bent. 13
Third Premise. B cannot be identical to SS because SS is straight while B is bent.
Conclusion. Direct Realism is false. We do not directly perceive SS; we are aware of SS only by means of a prior awareness of B.
The argument from perceptual variation (Russell’s table argument) - Russell put forward an argument that can be used against direct realism which drew attention to the table he was sitting at when he was writing about it
Russell was an empiricist so did believe that we get knowledge from our senses but he thought that our senses are prone to mistakes.
If the table looks and feels different from different angles, or from the same angle when perceived by different people, how can we be directly perceiving the table. There must be something happening between object and eye and mind.
Indirect realism
Indirect realism claims that we perceive physical objects which are mind-independent, but we do so via, or in virtue of, perceiving mind-dependent sense-data that are caused by and represent physical objects. We perceive sense-data immediately, and physical objects indirectly.
Sense data are mental images which we see exactly as they are but the represent physical objects in various ways (not always exactly as they are). Sense-data only exist while they are being perceived but the object itself can exist when it is not being perceived. Sense-data are private, physical objects are public.
An idea closely related to sense data is John Locke's distinction between primary and secondary qualities:
Issues with direct realism
Scepticism about the existence of mind independent objects (external world) - All we perceive is sense-data, so all we can know is sense data exists. There could be another cause of our sense data (evil demon, brain in a vat).
Russell’s reply - Bertrand Russell, an indirect realist, concedes that there is no way we can conclusively defeat this sceptical argument. However, he argues that the existence of a mind-independent external world is the best explanation for sense data.
Scepticism about the nature of mind independent objects - Scepticism is the view that we cannot know, or cannot show that we know, a particular claim. In this case; how can we know that the world is similar to how it appears to us in sense-data, or whether it is very different? Even if we can show that our sense data are caused by something that exists independent of our minds, can we establish what kind of a thing that cause is? We cannot tell a cause from its effects. If all you knew was smoke, would you be able to work out that it was caused by fire? If all we experience are sense-data, how can we know whether the world is similar to how it appears to us?
Indirect realism maintains that sense data are not only caused by the external world, but they also represent it. Locke argues that physical objects ‘resemble’ sense data. Therefore, there is some correlation between what we experience and the nature of the world. However, if all that I directly perceive is a representation of reality in my mind, then I can never directly perceive objects outside of my mind. We need to compare reality with the representation but without independent access to reality we cannot establish how accurate our perceptions are. This can be referred to as the ‘veil of perception’. It is due to this lack of direct access to mind independent objects that indirect realism leads to scepticism about the nature of the external world.
Idealism
Esse est percipi’ - ‘to be (or exist) is to be perceived’
Physical objects do not exist INDEPENDENT OF PERCEPTION
Berkeley called sense data, or whatever we are immediately aware of, IDEAS, and claimed that physical objects are a collection of ideas.
He agreed that all knowledge comes from experience – empiricist.
This means that if you do not have an experience of something, you cannot have a concept of it; so a blind person cannot have the concept of the colour red.
Berkeley’s attack on the primary/secondary quality distinction (pp. 13–15) Having persuaded Hylas to agree that secondary qualities are mind-dependent, Philonous (Berkeley) argues that the argument from perceptual variation applies equally well to primary qualities.
1 What looks small to me may look huge to a small animal.
2 What looks small from a distance looks large when viewed close up.
3 What looks smooth to the naked eye appears craggy and uneven under a microscope.
4 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.
5 Even motion isn’t constant. We measure the speed of motion by how quickly our minds work – to a creature that thinks much faster than us, e.g. a housefly, our fastest movements appear leisurely.
6 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.
7 Therefore, (1)–(5) show that we can’t say that an object has one real shape or size or motion, independent of how it is perceived.
8 Therefore, the primary qualities of objects are just as mind-dependent as secondary qualities.
Idealism criticisms
Idealism doesn’t explain illusions - If we see a stick/oar/pencil half in water, it looks crooked, but if all we have is mind dependent ideas, then what idea has cause the oar to be crooked rather than straight? If there is no physical oar out there in the world, why would it look different? Idealism doesn’t explain this.
Idealism leads to solipsism - Solipsism is the view that only oneself, one’s mind, exists. There are no mind-independent physical objects and there are no other minds either. Only my mind exists - there are no other minds nor are there any mind-independent objects or properties. It is not possible for me to know about the existence of anything apart from my mind. I cannot know if there are other minds or mind-independent objects.
God cannot play the role he does – Berkeley attempts to overcome several criticisms of idealism by using God as a permanent perceiver of all things. This allows objects to be in existence, even when not being perceived by me, and allows for other minds to exist – overcoming solipsism. However, if God cannot play this role, this would show Berkeley’s theory to be weak. There are several issues with the use of God in Berkeley’s philosophy; firstly, the use of God in a philosophical argument is often seen as weak because we can doubt God’s existence. Also, as an empiricist, Berkeley claims that all ideas must be traced back to an original sense experience, otherwise we cannot have a coherent concept of it. With God, this is not possible as we cannot have sense experience of God. Finally, Berkeley states that all we perceive are primary and secondary qualities, God does not have primary and secondary qualities and so we cannot perceive him. Therefore, we cannot have a coherent idea of God and he cannot play the role he does in Berkeley’s philosophy.
Scepticism about the existence of mind independent objects (external world) - All we perceive is sense-data, so all we can know is sense data exists. There could be another cause of our sense data (evil demon, brain in a vat).
Russell’s reply - Bertrand Russell, an indirect realist, concedes that there is no way we can conclusively defeat this sceptical argument. However, he argues that the existence of a mind-independent external world is the best explanation for sense data.
Scepticism about the nature of mind independent objects - Scepticism is the view that we cannot know, or cannot show that we know, a particular claim. In this case; how can we know that the world is similar to how it appears to us in sense-data, or whether it is very different? Even if we can show that our sense data are caused by something that exists independent of our minds, can we establish what kind of a thing that cause is? We cannot tell a cause from its effects. If all you knew was smoke, would you be able to work out that it was caused by fire? If all we experience are sense-data, how can we know whether the world is similar to how it appears to us?
Indirect realism maintains that sense data are not only caused by the external world, but they also represent it. Locke argues that physical objects ‘resemble’ sense data. Therefore, there is some correlation between what we experience and the nature of the world. However, if all that I directly perceive is a representation of reality in my mind, then I can never directly perceive objects outside of my mind. We need to compare reality with the representation but without independent access to reality we cannot establish how accurate our perceptions are. This can be referred to as the ‘veil of perception’. It is due to this lack of direct access to mind independent objects that indirect realism leads to scepticism about the nature of the external world.
Idealism
Esse est percipi’ - ‘to be (or exist) is to be perceived’
Physical objects do not exist INDEPENDENT OF PERCEPTION
Berkeley called sense data, or whatever we are immediately aware of, IDEAS, and claimed that physical objects are a collection of ideas.
He agreed that all knowledge comes from experience – empiricist.
This means that if you do not have an experience of something, you cannot have a concept of it; so a blind person cannot have the concept of the colour red.
Berkeley’s attack on the primary/secondary quality distinction (pp. 13–15) Having persuaded Hylas to agree that secondary qualities are mind-dependent, Philonous (Berkeley) argues that the argument from perceptual variation applies equally well to primary qualities.
1 What looks small to me may look huge to a small animal.
2 What looks small from a distance looks large when viewed close up.
3 What looks smooth to the naked eye appears craggy and uneven under a microscope.
4 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.
5 Even motion isn’t constant. We measure the speed of motion by how quickly our minds work – to a creature that thinks much faster than us, e.g. a housefly, our fastest movements appear leisurely.
6 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.
7 Therefore, (1)–(5) show that we can’t say that an object has one real shape or size or motion, independent of how it is perceived.
8 Therefore, the primary qualities of objects are just as mind-dependent as secondary qualities.
Idealism criticisms
Idealism doesn’t explain illusions - If we see a stick/oar/pencil half in water, it looks crooked, but if all we have is mind dependent ideas, then what idea has cause the oar to be crooked rather than straight? If there is no physical oar out there in the world, why would it look different? Idealism doesn’t explain this.
Idealism leads to solipsism - Solipsism is the view that only oneself, one’s mind, exists. There are no mind-independent physical objects and there are no other minds either. Only my mind exists - there are no other minds nor are there any mind-independent objects or properties. It is not possible for me to know about the existence of anything apart from my mind. I cannot know if there are other minds or mind-independent objects.
God cannot play the role he does – Berkeley attempts to overcome several criticisms of idealism by using God as a permanent perceiver of all things. This allows objects to be in existence, even when not being perceived by me, and allows for other minds to exist – overcoming solipsism. However, if God cannot play this role, this would show Berkeley’s theory to be weak. There are several issues with the use of God in Berkeley’s philosophy; firstly, the use of God in a philosophical argument is often seen as weak because we can doubt God’s existence. Also, as an empiricist, Berkeley claims that all ideas must be traced back to an original sense experience, otherwise we cannot have a coherent concept of it. With God, this is not possible as we cannot have sense experience of God. Finally, Berkeley states that all we perceive are primary and secondary qualities, God does not have primary and secondary qualities and so we cannot perceive him. Therefore, we cannot have a coherent idea of God and he cannot play the role he does in Berkeley’s philosophy.