Perception

Question 1

Direct Realism

Answer 1

1. We perceive objects independent of the mind.
2. This means we see things because they are there.
3. So the object is the same independent of being seen.
4. Therefore, they exist mind-independently.

Question 2

Argument from Illusion

Answer 2

1. We perceive something having some property x (e.g. a bent stick.)
2. When we perceive something having some property ‘x’, then there is something which has this property.
3. In an illusion, the physical object does not have the property ‘x’ (the stick is not bent.)
4. Therefore, what has the property ‘x’ is something mental: sense data.
5. Therefore, in illusion we see sense data, and not physical objects immediately.
6. Illusions can be ‘subjectivity indistinguishable’ from veridical perception.
7. Therefore, we see the same thing, namely sense data, in both veridical perception and illusion.
8. Therefore, in all cases we see sense data and not physical objects directly.
9. Therefore, direct realism is false.

Question 3

Argument from Hallucination

Answer 3

1. In a hallucination, we see something having the property ‘x’.
2. When we perceive something having property ‘x’ then something has that property.
3. In an hallucination we don’t perceive a physical object at all (unlike in illusion.)
4. Therefore, what we perceive is mental sense data.
5. Hallucinations are experimented that are ‘subjectively indistinguishable’ from veridical perception.
6. Therefore, we see the same thing, namely sense data, in both veridical perception and in hallucination.
7. Therefore, in all cases, we see sense data and not physical objects immediately.
8. Therefore, direct realism is false.

Question 4

Causal Argument

Answer 4

1. When we perceive an object there is a long chain between the mind-independent object and me perceiving it’s (e.g. Light from object-focus percent on retina-nerve impulse to brain-image in brain.)
2. So I cannot perceive it directly as there is something between the object and the perceived.
3. So we cannot have direct contact with the object itself.
4. This suggests that we don’t perceive the object directly, but indirectly.
5. Therefore, our perception of reality is based upon a causal chain of events between the perceived and the perceived thing.
6. Therefore, direct realism is false.

Question 5

Time-Lag Argument

Answer 5

1. We cannot perceive physical objects when light is reflected from them to out retina.
2. There is a time difference between the reflection of light from an object to the time it reached our eyes e.g. The light from the sun takes 8 minutes to reach our eyes.
3. If something no longer exists anymore (e.g. a distant star) we cannot perceive it.
4. Time lag between physical objects and the time it takes to reach our eyes is incompatible with direct realism, as given the time lag we cannot directly perceive physical objects as they presently are at the time lag of our perception.
   5therfire, direct realism is false, we don’t perceive physical objects directly.