Perception as a source of knowledge

Direct Realism - we perceive mind-independent objects directly (without a mediator)
1. Strengths
  1. It explains why people have the same reactions to the same things as me
  2. It is coherent
  3. It is simple (Occam's razor, only includes the object and the perceiver)
2. Weaknesses/critiques
  1. Hallucination - if we can hallucinate some things, how can we know that all we are seeing is real? Attacks 'realism'.
    1. The argument doesn't work because it is talking about a mind-dependent object. Therefore, there is nothing to argue with, as what you are perceiving isn't even really an object. This is backed up by the people's testimony, as people who have experienced hallucinations say that they are aware that they are hallucinating.
  2. Illusion - If we know that what we are seeing is not how it is in reality, then we cannot really know that anything is what we perceive it to be like. Therefore, there must be a mediator to warp our perceptions. Attacks 'direct' and 'realism'
    1. Still a direct perception of reality as it is, what we are perceiving is just the light particles refracting around the pencil.
  3. Time-Lag - If the stars we are seeing are not the stars as they are right now, then we are not perceiving them directly. Attacks 'direct'
    1. This misunderstands the meaning of 'direct' as we are still perceiving things as they are, it just takes a while for the light particles to get to our eyes.
  4. Perceptual variation - Russel points out that people's perceptions of one thing can differ immensely, be it of one person or different people's perceptions. He uses the example of a table, as when we move slightly then we see a different shade of brown. Because of this, Russel argues that we must be perceiving M-I objects through a mediator, as the qualities of the table are different to different perceptions.
    1. Relational Properties - include colour. So the colour of the table changes IN RELATION to other things, like how far away you stand. Still a direct perception of an m-i object.
Indirect Realism
1. Locke - Said that the M-I objects give us 'ideas', which are our perceptions of the world, and our perceptions of primary qualities show that things are M-I, but we must be perceiving things indirectly, which is why people's perceptions of things differ (secondary qualities).
  1. How to tell primary qualities apart from secondary ones.
    1. Primary qualities can be accessed by more than one sense.
    2. Primary qualities are ESSENTIAL to an object. It wouldn't be that object if it didn't have it.
    3. Primary qualities can be measured.
2. Russel - called Locke's 'ideas' 'sense-data'; these are what we pick up using our organs; so it is our senses that are the mediators.
3. Weaknesses/critiques
  1. We can't know anything about the m-i world if we are not perceiving things as they are.
  2. We can't even be sure that things exist if we are not perceiving things directly. We only know about what our sense-data tells us, and not about something's existence.
    1. Locke points out the involuntary nature of our experiences. We can choose what we imagine, r what we think about. We cannot choose what we perceive.
    2. Locke & Trotter-Cockburn - The coherency of our perceptions.
    3. Russel's 'best hypothesis' - since he cannot prove or disprove that there are or are not m-i objects, Russel decides to treat both as hypotheses. He comes to the conclusion that there are m-i objects, as the other option would include taking people's testimony, and he cannot be sure that people exist. It is also the simplest conclusion (Occam's razor).
Berkeley's Idealism - There are no mind-independent objects.
1. 'To be is to be perceive and to perceive'
2. An object is a collection of ideas
3. Berkeley argues that any form of realism leads to sceptiism
4. His Arguments.
  1. The Master Argument
    1. 1) If we can know that MI objects exist then we must be able to conceive of a MI object. 2) An MI object is one that exists even when it is not being conceived by a mind (unconceived). 3) Whenever I conceive of MI objects, they are, by definition, conceived. 4) It's logically impossible to conceive of an unconceived object. 5) Therefore, we cannot know of MI objects.
      1. But conceiving and perceiving are NOT the same things. He conflates the two.
      2. (Russel) Thoughts can't exist outside the mind, but objects that are thought about can.
    2. 'Killer blow'
  2. The attack on the primary/secondary quality distinction - he says that you can't say that m-i objects exist because of the primary/secondary quality distinction, as primary qualities are subject to perceptual variation too.
    1. Size depends on how far away you are
    2. speed depends on yours
    3. Something's solidity depends on how strong you are
    4. However - we could say that sense-data changes, but the objects we are perceiving do not, as if we kept a ruler next to an object and moved further away it would always say they are the same size
  3. Argument for God
    1. 1) As (the ideas that comprise) physical objects are m-d, there are three possible causes of my perceptions: ideas, my mind, and another mind. 2) Ideas themselves don't cause anything. 3) If physical objects depended on my mind, then I would be able to control what I perceive. 4. But I can't. Perception is quite different to imagining; we are more passive - the sensations just occur to us, and we can't control them. Imagination is voluntary, but perception is involuntary. 5. Therefore, physical objects don't depend on my mind. 6) Therefore, physical objects must exist in another mind, which then wills that I perceive them. 7. Given the complexity and systematicity of our perceptions, that mind must be God.
      1. Counter: Berkeley recognises the issue that if what we are perceiving is God's perceptions that he is pushing onto us, then that means that he is experiencing pain and he is not meant to have faults. If it is his mind that creates these things, like pain, then he must also experience them.
        But Berkeley counters that God doesn't experience ideas like pain, he only creates them and imposes them onto us. He is not subject to these laws himself.
5. Critiques
  1. Doesn't explain regularity/continuity
    1. God is what is constantly perceiving everything, keeping it in existence.
  2. Hallucinations and illusions - If everything is an idea, then how can we tell the difference between hallucinations and 'normal' perceptions. And how is an illusion not reality if everything we perceive involuntarily is all there is?
    1. Berkeley says that we can tell the difference by the regularity of past experience. We don't often see elephants floating through the room or pencils that are bent.
      1. But what if these hallucinations/illusions just kept happening?
      2. This doesn't explain WHY they happen, only how we tell the difference.
      3. This makes hallucinations/illusions the same thing when they are not.
  3. Idealism leads to 'the trap of solopsism'. We can't be sure that other minds actually exist.
    1. This could just be accepted as an unfortunate side-effect
    2. Some say that others having minds is just the simplest solution

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