Londoner wrote:Terrapin Station wrote:
My side of the philosophy perception debate is that we're directly perceiving objective things (where again, because for some reason it's so easy to overlook this, one should note that I'm not saying that we're not perceiving objective things, we are perceiving them). My side of the debate is not that we're instead "perceiving" mental images, so that there's another level of remove somehow from the objective things.
By 'objective things', do I understand that these are 'things-in-themselves', 'noumena', all that stuff? So that when you say we perceive them 'directly', you are saying we see them in their entirety, rather than just those aspects that manifest themselves to our senses as phenomena? Indeed, that there is no such distinction to be made?
Me: One reason I have for saying this is because people with different sensory abilities (e.g. colour blindness) will have different mental images of what a tree is.
Naive realism very well agrees that various factors, such as color blindness, can interfere with accurate perception of objective things.
That being the case, how do we know which perception is 'accurate'? We can compare our own perception to others, but only second hand through the medium of language. If everyone agrees that the word 'green' means 'the colour of grass' then everyone will agree that the grass is green, even if we all see different colours. And even if we could get over that hurdle, democracy amongst humans would not prove accuracy; other creatures have eyes that are in some ways superior to ours. Why don't they get a vote?
Aside from that, the same tree is not going to be perceived identically by any two person for these two reasons:
(1) Nominalism is true. When we're talking about whether the same tree is perceived identically by two different people, we're talking about two different persons' perceptions. Person 1's perception is not identical to person 2's perception simply because nominalism is true. It's two different instances, numerically distinct, of perceptions, and two numerically distinct things are not identical.
(2) A general, thoroughgoing relativism is the case. Every existent has at least some different properties at different "reference points," there are no "reference point-free reference points," and there are no objectively-preferred reference points. Two different people necessarily experience the "same thing" (such as the "same tree") from two different reference points. The tree in question has at least some different properties at reference point A and reference point B. Plus we're also talking about the properties of all the other stuff involved--the lightwaves, the atmosphere, etc. that obtain between the surface of the tree and the surface of the person's eyes, for example.
That too. I would say we are aware of such things, so the idea we form of a tree necessarily goes beyond our own perception of that tree. It will be part of the way in which I understand the world generally. Thus, because I have found things generally have backs, my idea of a tree is of an object that exists in three dimensions, even though I can only see the front.
Stereoscopic vision creates depth perception, in addition light reflects differently on different parts of a curved surface thus shadowing indicates knowledge of the back of a tree.
Me: I also pointed out that if we simply assumed that normal human senses just happened to be perfect for capturing the entirety of external objects,
No one said anything about the "entirety" of anything.
But surely the thing-in-itself must comprise of all of that thing, not just the bits we happen to see? The 'tree-in-itself' must be the whole tree, not just the bit nearest me. If we can only capture an aspect of the tree, then what we claim to be the 'objective thing' would be something we ourselves had constructed.
We can only construct something truthful in our minds once we've seen it or something similar previously.
Me: this would create a paradox; that when we used these reliable tools to examine how our eyes work, we find that our ideas of external objects are reconstructed from electrical signals. That there is no way that our eyes can somehow capture external objects directly.
"Directly" means that it's not a perception of a mental image. Not that it's not a perception.
I do not see how we can distinguish between perceiving something and creating a mental image of it. The two seem one and the same thing.
Go out side near a tree. Now with open eyes look at it directly, there you go. Now shut your eyes and create a mental image of that same tree, there you go! Are they identical? There you go! 
I suppose we could try to separate the two, but in that case what form would the perception have before it was a mental image?
It could be a photon, before it entered the eye, but then we would have the odd situation of the universe being full of perceptions that nobody perceives. It could be an electrical event in the nerve, but then we would have to say we perceive electricity, rather than objects. I think it only makes sense to speak of perception as a type of thought, as something we create in response to the stimulus of the photon and the electrical event, that we posit as having an external cause.
I would add that I do not think it is 'direct' in the sense that the thought is one fixed thing either, i.e. that a particular set of stimuli create a particular mental image. I think that we can and do apply a range of interpretations to the same set of stimuli, select within the set or ignore them all, or add knowledge obtained from some entirely different source.
