epistemology perception as a source of knowledge Flashcards
key term- immediate objects of perception
means the things which we perceive directly.
support for direct realism
+avoids scepticism: we know about it because our senses provide immediate access to its true nature.
+has explanatory power: if im directly aware of physical reality + its properties explains why i can execute range of practical daily actions e.g finding food.
+explains why i percieve what i do: e.g i see the tree is green because the tree is green.
+explains why we agree about what we percieve and is in tune with out senses that occupy same universe as everyone else.
Problem- Bertrand Russel perceptual variation ( criticism)
differences in perceptions variation provide a problem for direct realism
e.g when i stand on one side of the room a shiny wooden table may have a white spot where the light is shining on it. But to someone standing on the other side of the room there may be no white spot.
But the white spot is either there or it isn’t - it can’t be both!
means = one of us is not perceiving the table directly as it is.
Russel more examples with the table:
shape of the table- from directly overhead may appear rectangular. few meters away may look kite-shaped.
Again- can’t be both
examples: highlight the differences in our perception.
according to direct realism: there should be no differences between perception and reality.
all these variations in perception suggest that there is no real way to perceive the world
possible response to russel relation properties
direct realism can respond by refining the theory and introducing the idea of relational properties.
argument from illusion (criticism)
DR says we percieve the external world directly as it is. If true how is it that reality can be different to our perception of it?(Ayer)
Example : when a pencil is placed in a glass of water, it looks crooked. But it isnt really crooked.
If direct realism is true, the external world would be exactly as we percieve it. However in case of illusion there in an obvious difference between perception + reality.
If things appear to be different from the way they actually are then we dont periceve the world itself accuaretly: we percieve sense data. Therefore, direct realism is false.
possible response illusion criticism
Direct realist could reply that the pencil has the relational property of looking crooked to certain pericevers (even tho it isnt). In the example, direct realism would argue it appears bent because we are accurately percieving light refraction.
+ we can occationally misinterpret what we periceve.
argument from hallucination
more extreme version agrument from illusion. DR says when we percieve something we are percieving something in the external world (directly). But during halluctions- we percieve things that arent even there.
Whats causing these perceptions? It cant be the external world - at least not directly- because there is no external object being percieved at all.
Argument points out- hallucinations (illusory perceptions) are often qualitavely indistguishable from verdical perceptions (i.e hallucinations look as realistic as real objects do).
summary hallucination (arugment structure)
p1. direct realism states that we percieve the world directly + accuartely.
p2. In an illusion, we percieve an object as having particular properties.
p3. the real object does not have these properties/ no such object exists
p4. if things appear to be different from the way they actually are, then we do not percieve the world accurately.
c. Therefore, direcet realism is false.
time lag argument
The sun is 149,600,000km from earth. Light travels at 299,792,458 meters per second.
This means it takes approximately 8 minutes for light to reach earth. So, when you look at the sun, you are seeing it as it was 8 minutes ago- i.e there is a difference between the sun itself + your perception of it. In other words you are not percieving the sun directly.
time lag summary (argument structure)
- direct realism states that we percieve the external world directly, immediately + accurately.
- light from stars + other distant objects takes so long to reach our eyes that we cannot see them as they are at the moment.
- If things appear to be different from the way they actually are, then we do not percieve the world directly + accurately.
- Therefore, direct realism is false.
time lag response
the direct realist can argue that this response confuses what we percieve with how we percieve it. Yes, we percieve objects via light + sound waves + yes, it takes time for these light + sound waves to travel through space. But what we are percieving is still a mind-independent object- it’s just we are percieving it as it was moments ago rather than how it is now.
indirect realism meaning
the view that:
- the external world exists independently of the mind (hence, realism)
- but we percieve the external world indirectly, via sense data (hence, indirect).
Indirect realism says the immediate object of perception is sense data. This sense data is cause by + represents, the mind-independent external world.
indirect realism summary
- realist theory. so, retains the belief that material objects exist independently of the mind.
- however draws distinction betwee reality of these objects + the way they appear.
- 3 elements in perception: perciever, real objects that they periceve, also appearance of objects to the perciever.
- what we are directly aware of are appearances, locke ‘ideas’ and russel ‘sense data’. r representations of reality.
- must infer, on the basis of these sense data, the nature of reality. because perception invovles this interference it is indirect.
sense data overview
sense data =the content of perceptual experience
not a psysical thing, exists in the mind. can be caused by + represent mind-independent objects.
sense data private and individual.
john locke distinction of primary + secondary qualities.
what are lockes primary qualities?
(objective)
properties inherent in the object itself
-size
-shape
-motion
-number
what are Locke secondary qualities?
(subjective)
powers of an object to cause sensations in humans
- colour
-taste
-smell
-feel
what does locks primary and secondary qualities illustrate?
One example is porphyry= a red and white stone.
Locke says when you prevent light from reaching porphyry “its colours vanish”. However primary qualities remain.
his distinction between P + S qualities used to support INDIRECT REALISM.
support for Lockes primary qualities
Locke- primary qualities are ‘utterly inseparable’ from an object. Means that - however the object is altered its parts must retain some shape, size, position and so on, even if we can no longer see the parts. without the qualities it wouldn’t be material at all. Therefore, primary qualities must be essential to material objects and are retained by the objects wether or not anyone perceives them.
support for locked primary qualities in summaries argument structure
P1 if you continually divide an object the parts must retain the primary qualities even when they are too small to be perceived.
C therefore primary qualities must exist mind independently.
support for locked secondary qualities distinction
By contrast secondary qualities do alter or vanish. colours are only visible in the light and change depending on light. So Locke concludes the secondary qualities both depend on the primary qualities and require a mind to appear and so are not in the objects themselves as we perceive them.
support for locked secondary qualities in argument structure
P1 when we pound an almond we merely change the shape of its parts.
P2 but the colour and taste of the almond also change.
C so, the change in colour and taste is caused by the change in the shape of the almonds parts.
What is a problem for indirect realism?
Problem for indirect realism is that it leads to SCEPTICISM about the nature and existence of the external world.
PROBLEM: SCEPTICISM overview/ key points
- according to indirect realism we are directly aware only of sense data + must infer the existence of objects beyond the mind.
-however, our senses can deceive us.
-worse, it is conceivable that our sense data do not correspond with any material reality, if for example my brain is in a vat or there is a powerful demon bent on deceiving me.
-these possibilities show that the interference is not valid and so not sufficient for knowledge.
problem: scepticism
what is the ‘veil of perception’?
We only know what e are directly aware of. Since we cannot directly observe reality we cannot know it exists. = called veil of perception is the problem for it says that our sense data constitute a veil between us and reality which we cannot penetrate to discover the material world.
