Friday, May 07, 2010

Do we perceive physical objects directly? Maybe not

A redated post (with a spelling correction in the title). 

Do we perceive physical objects directly, or are the immediate objects of our experience our own sense-data, which may be caused by some state of the physical world? Given that we can certainly have non-veridical experiences, what are we aware of in those cases? What is the direct object of our awareness?

Lewis wrote: “It is clear that everything we know, beyond our immediate sensations, is inferred from those sensations.” He goes on to say

“I do not mean to say that we begin, as children, by regarding our sensations as “evidence” and then arguing consciously to the existence of space, time, matter, and other people. I mean that, if we are old enough to understand the question, our confidence in the existence of anything else is challenged, our argument in defence of it will have to take the form of inferences from our immediate sensations. Put in its most general form the inference would run “Since I am presented with colours, sounds, shapes pleasures, and pains which I cannot perfectly predict and control, and since the more I investigate them the more regular their behaviour appears, therefore there must exist something other than myself and it must be systematic.”

In my study of this passage, and contrary to John Beversluis, I have supposed that this passage is compatible with what is called the direct realist position on perception. We could perceive physical objects directly, nevertheless perhaps when we are challenged about those perceptions we perform inferences in defense of the veridicality of those perceptions.

Nonetheless, we might ask whether direct realism is correct. Edward Feser, in his book Philosophy of Mind: A Short Introduction (Oneworld, 2005), suggests that there is a powerful argument for the indirect realist view of perception:

1. By stimulating the brain so as artificially to produce a neural process that is normally associated with a certain veridical experience, it is possible in principle to bring about a hallucination that is subjectively indistinguishable from that experience.
2. But if the immediate causes of veridical perceptual experiences and their hallucinatory counterparts are of the same sort, then these effects must be of the same sort as well.
3. In the case of hallucinations, the effect is obviously direct awareness not of any external physical object, but rather of a subjective mental, perceptual, representation of an external object.
4. So in the case of veridical perceptual experiences too, what one is directly aware of must be a subjective perceptual representation.

So, do we perceive physical objects directly? And, if we don’t, does this have any effect on the debate between materialists and their opponents?


Mike Darus said...

On the basis of this information, I would need to side with Lewis with direct realism. Even if Fever's experiment were possible (apparently it currently is not), it would likely be a simulation of sensory input, not a veridical experience. The two things that would then be the same would be sensory experience and the simulation of sensory experience. The experiment would also need to differentiate between a new, unique halucination and one that is merely a combination of memories that are excited by the brain stimulation.

There is a deeper level here. You may need to define "we" and "perceive."

"Now we see through a glass dimly."

Dennis Monokroussos said...

Feser's argument (which goes back to Locke, if not earlier) isn't compelling - one could elude indirect realism with e.g. an adverbial theory of appearance. Rather than being aware of some third thing, we're being appeared to treely. When perception is veridical, the cause is normal visual processes working properly in an appropriate environment; when it's not, at least one component is missing.

Also, there's a distinction to be made between different kinds of intermediates. It's reasonable to reject an intermediate object of awareness, but far less reasonable to reject a mediating process. Vision is an incredibly complex process, but our visual beliefs are inferentially and objectually direct.

Anonymous said...

One also needs to take into consideration the experiments of Bruner and Postman, which demonstrate that perception is heavily dependent upon prior conceptual resources. We might be able to perceive objects CORRECTLY with the right conceptual resources (sort of like Kant's categories) but I don't think we ever perceive objects DIRECTLY. There is too much neuroscientific and cognitive science evidence to support the CONSTRUCTION of perception, with feedback and constraint from the gross material environment, of course.

For a fascinating study of the implications of these findings for the debate between materialism and theism, Arbib and Hesse's "The Construction of Reality" is simply required reading.

Anonymous said...

perceive is spelled preceive in your heading!

Anonymous said...

If indirect realism is true, what about Berkeley's argument (one of them, at least) for idealism in the Treatise? He says if there were a material world, we wouldn't know about it (what we perceive are ideas, not the world, so we wouldn't know it existed by our senses; but neither by reason because there is no necessary connection between our being appeared to in an x kind of way and there being an x there), and if there isn't, then we wouldn't know about it--so either way we don't know about it. So why bother positing it?

Of course, there may be arguments that a material world's causing our sense perceptions makes more sense of the nature of our perception than God's causing them does, but what would an argument like that look like?

Jason Pratt said...

For those who don't know, this quote is from Lewis' crucial chapter 3 of Miracles: A Preliminary Study (2nd edition), "The Cardinal Difficulty of Naturalism" (page 14 in the MacMillan 1978 printing); this is how he begins deploying his version of the theistic (or contra-atheistic) Argument from Reason.

I'm a little fuzzy, though, on how this statement counts as an affirmation of direct realism, much less how it necessarily requires it. I agree that the statement is compatible with direct realism, but it also seems compatible with Feser's indirect realism--I might even call it basically tantamount. The sensation is what we are directly 'knowing' or rationally apprehending by action (not merely reacting in stimulation to).

Feser's conclusion (element 4, "In the case of veridical perceptual experiences too, what one is directly aware of must be a subjective perceptual representation.") looks to be the same thing Lewis is saying. The veridical GIT (Lewis' "inference in its most general form") uses as data direct awareness of subjective perceptual representation ("colours, sounds, shapes, pleasures and pains")--plus the extra data element "which I cannot perfectly predict and control".


Jason Pratt said...

In my book Sword to the Heart (which is an extensive followup/expansion to Lewis' MaPS), a significant portion of Section Three (currently unavailable anywhere), where I argue in favor of supernaturalistic theism vs. naturalistic theism (having already argued in favor of theism vs. atheism in the prior Section), is based on Lewis' general inferential train as quoted by Victor here. (This is a little different from Lewis' deployment of the GIT, as he is setting up mainly against atheism not against philosophical naturalism per se; his argument against theistic naturalism is given later in MaPS on somewhat different grounds.)

The longest chapter of Section One, however, deals extensively with what amounts to Feser's indirect realism in conjunction with what amounts to Lewis' GIT--by means of Robin Williams' famous comedy routine about a golfer on cocaine believing a snake is in the hole of the green.

A second edition of the chapter can be found at the Christian Cadre starting here in four parts (though the first three parts are most relevant). A third edition can be found in several parts here on the EU forum as part of my Bite-Sized Metaphysics series.

Shackleman said...

I can think of no _subjectively_ *qualitative* difference between what I perceive when I'm awake and what I perceive when I'm dreaming.

Given dualism though, I can explain dreams as the immaterial "mind" playing with the physiological brain to "induce" the perception of sense-data. Whereas during wakefulness, the sense-data is arrived at because of external, rather than internal forces.

But, if there is no immaterial self, then the naturalist falls victim to the charge that they could be brains in vats, and I doubt they can prove otherwise.

Shackleman said...

Mr. Pratt,

You've been influential to me over the years. I wish you had a single unified place where you posted and discussed your thoughts and writings. It's difficult to sift through everything over at CC. ALl good stuff, but if I'm just interested in reading stuff from you, is there some place I can go to conveniently get it?

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