AS philosophy indirect and direct arguments: epistimology

The Time-lag argument - Indirect realism
1. 1) Perception is dependent on information about the external world reaching the brain, via the sense organs, and then being processed there, all of which takes a finite amount of time, however small.
  1. 2) Therefore, the content of one's perceptions always lags behind the external world, however slightly.
    1. 3) Therefore, when perceiving changes in the external world there will always be a difference, however small, between the content of one's perceptions and the external world at the same moment in time.
      1. 4) If there is a difference, however small, between X and Y at the same moment in time, then X is not Y.
        5) Therefore, the content of one's perceptions is not the external world.
        6) Perception is, by definition, the process by which one experiences the external world, via the sense organs.
        7) Therefore, if the content of one's perceptions is not the external world itself, then it must at least be a representation of it.
        8.) If the content of one's perceptions is merely a representation of the external world, and not the external world itself, then the only conceivable location of that representation is inside one's mind.
        9) Therefore, the content of one's perceptions is merely a mental simulation of the external world. In other words, what one directly experiences as being 'out there' is in fact located inside one's mind
The argument for hallucination
1. Indirect
  1. 1) There are perceptual experiences, such as illusions and hallucinations, in which what we experience are not the properties of physical objects.
    1. 2) When we perceive something having some property F, then there is something that has this property.
      1. 3) In such cases, given that what we perceive is not the way the world is, what we perceive are sense-data.
        4) Such cases are subjectively indistinguishable from veridical perception.
        5) When two perceptual experiences are subjectively indistinguishable, they are perceptual experiences of the same thing. (This claim is the best hypothesis, given (4).)
        6) Therefore, we always perceive sense-data (not just in cases in which what we perceive is not the way the world is).
        7) Nevertheless, except in hallucinations, it still makes sense to say we perceive the world. In cases of both veridical perception and illusion, the sense-data we perceive are caused by and represent physical objects. This representation can be accurate or inaccurate in certain ways – physical objects may be as they appear to us, or they may differ in certain ways.
        8) Therefore, we perceive physical objects indirectly, via sense-data.
2. Direct
  1. We can experience perceptual hallucinations – not just visual ones, but auditory and olfactory hallucinations as well.
    1. 1 In a hallucination, we perceive something having some property F.
      1. 2 When we perceive something having some property F, then there is something that has this property.
        3 We don’t perceive a physical object at all (unlike the case of illusion).
        4 Therefore, what we perceive must be mental – sense-data.
        5 Hallucinations can be experiences that are ‘subjectively indistinguishable’ from veridical perceptions.
        6 Therefore, we see the same thing, namely sense-data, in both hallucinations and veridical perception.
        7 Therefore, in all cases, we see sense-data, and not physical objects, immediately.
The argument for illusion
1. Direct
  1. 1) We perceive something having some property, F (e.g. a stick that is crooked).
    1. 2) When we perceive something having some property F, then there is something that has this property.
      1. 3) In an illusion, the physical object does not have the property F (the stick is not crooked).
        4) Therefore, what has the property F is something mental, a sense-datum.
        5) Therefore, in illusions, we see sense-data, and not physical objects, immediately.
        6) Illusions can be ‘subjectively indistinguishable’ from veridical perception.
        Truthful; veracious: veridical testimony.
        7) Therefore, we see the same thing, namely sense-data, in both illusions and veridical perception
        8) Therefore, in all cases, we see sense-data, and not physical objects, immediately.
2. Indirect
The argument for perceptual variation
1. 1 There are variations in perception.
  1. 2 Our perception varies without corresponding changes in the physical object we perceive. (For instance, the desk remains rectangular, even as the way it looks to me changes as I look at it from different angles.)
    1. 3 Therefore, the properties physical objects have and the properties they appear to have are not identical.
      1. 4 Therefore, what we are immediately aware of in perception is not exactly the same as what exists independently of our minds.
        5 Therefore, we do not perceive physical objects directly.
2. Direct
3. Indirect
  1. 1 There are variations in perception.
    1. . 2 Our perception varies without corresponding changes in the physical object we perceive. (For instance, the desk remains rectangular, even as the way it looks to me changes as I look at it from different angles.)
      1. 3 Therefore, the properties physical objects have and the properties they appear to have are not identical.
        4 Therefore, what we are immediately aware of in perception is not exactly the same as what exists independently of our minds.
        5 Therefore, we do not perceive physical objects directly.

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AS philosophy indirect and direct arguments: epistimology

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