AS philosophy indirect and direct arguments: epistimology

AS philosophy indirect and direct arguments: epistimology

1. The Time-lag argument - Indirect realism

   • 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.
     • 2) Therefore, the content of one's perceptions always lags behind the external world, however slightly.
       • 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.
         • 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

2. The argument for hallucination

   • Indirect
     • 1) There are perceptual experiences, such as illusions and hallucinations, in which what we experience are not the properties of physical objects.
       • 2) When we perceive something having some property F, then there is something that has this property.
         • 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.
   • Direct
     • We can experience perceptual hallucinations – not just visual ones, but auditory and olfactory hallucinations as well.
       • 1 In a hallucination, we perceive something having some property F.
         • 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.

3. The argument for illusion

   • Direct
     • 1) We perceive something having some property, F (e.g. a stick that is crooked).
       • 2) When we perceive something having some property F, then there is something that has this property.
         • 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.
   • Indirect

4. The argument for perceptual variation

   • 1 There are variations in perception.
     • 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.)
       • 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.
   • Direct
   • Indirect
     • 1 There are variations in perception.
       • . 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.)
         • 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.