Friday, May 30, 2008

Do We Preceive Physical Objects Directly? Maybe not

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?

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At 5/30/2008 04:54:00 PM , Blogger Darek Barefoot said...


Great topic! A Kantian question. Appearance versus the thing-in-itself. It seems to have vexed and perplexed C. S. Lewis's philosopher contemporaries such as G. E. Moore and A. J. Ayer (maybe it went along with double initials instead of first names). They bequeathed to us the term, "sense-datum," if I'm not mistaken. I think philosophers just got tired of wrestling with the question and decided that parsing sentences was easier.

Or maybe the question was taken over by science. Einstein's relativity theories proposed that spatial and time features are nothing more or less than what they are observed (measured) to be. For someone rocketing past earth at near lightspeed, the earth will not merely appear ellipsoid, it will BE ellipsoid like a cat's pupil, while for us the earth will remain an oblate spheroid. Neither observation will be represent reality better than other.

But Einstein was only comfortable with his own version of the mystery. He found it objectionable in quantum mechanics. There was a famous confrontation between Einstein and Werner Heisenberg that went, pretty much, like this:

Einstein: You can't actually believe that an electon is nothing more than what we observe of it!

Heisenberg: But this is much like what your own relativity proposes . . .

Einstein: I may have reasoned that way, but it is nonsense nevertheless . . .

How can you know something indirectly without knowing it first directly? If you see the apple fall from the tree, when an apple hits the top of your head at night and you cannot see the tree, you may know indirectly where it came from. But what if the tree were the kind of thing that in principle can never be seen? What then gives you the impression that you know where the apple came from?
If "seeing the tree" means "experiencing the sight of the tree," then the tree is "known" at a remove, as you say.

If the windowless room I am in were on quiet motor and bearings so that it could begin spinning around, I would have a hard time telling spotaneous motorized spinning of the room from an unexpected dizzy spell. But how could I possibly imagine the illusion of the room spinning if objects never truly spin? The conception of the illusion is parasitic, so to speak, on the reality of movement of objects.

The world-as-thought-about immediately sunders itself from the world-as-experienced, but then reason brings the two back together. I think naturalism is more challenged by this than a mentalistic view, but I can't claim to have worked it out as an argument.

At 5/30/2008 06:02:00 PM , Anonymous Alan said...


Long time no post. A few random remarks:

-- It's probably unnecessary to mention this source to such philosophically savvy readers, but: The Stanford Encyclopedia of Philosophy has several excellent articles on this subject. Tim Crane's The Problem of Perception" and L. Bonjour's "Epistemological Problems of Perception" both deal with the crucial issues, and Susanna Siegel's "The Contents of Perception" is also relevant.

-- Following Bonjour, I think it's useful to distinguish between two different arguments for indirect realism, which Feser conflates: the Argument from Illusion and the Argument from the Scientific Account of Perception. Basically, the idea is that we knew about perceptual illusions, etc., for centuries before we had any notion of how the physiology of perception works, and so the Argument from Illusion can be mounted independently of any claims about the brain or nervous system (and in fact was, by the 17th and 18th century empiricists.) Note furthermore, that versions of the argument can appeal to a wide range of different perceptual phenomena: illusions, hallucinations, and perceptual relativity (i.e., a disk looking like an ellipse when viewed at an angle.)

-- I notice that this is a repost of a post on DI1 about a year ago, and you got a few commenters on that post. Mike D. said

"Even if Fever's [sic] experiment were possible (apparently it currently is not). . ."

The way that Feser expresses the argument in the passage you quote is open to that objection, but a more careful formulation of the argument is not. Here's Bonjour's version of the same point:

(i) the fact that the character of the resulting experience and of the physical object that it seems to present can be altered in major ways by changes in the conditions of perception or the condition of the relevant sense-organs and the resulting neurophysiological processes, with no change in the external physical object (if any) that initiates this process and that may seem to be depicted by the experience that results; (ii) the related fact that any process that terminates with the same sensory and neural results will yield the same perceptual experience, no matter what the physical object (if any) that initiated the process may have been like.

There's no single "experiment" involved, rather a vast amount of evidence both from laboratory experimentation and everyday experience; and there's no appeal to the possibility of producing a full-fledged "hallucination", but rather to a whole range of sensory alterations and distortion.

-- Dennis Monokroussos made reference to the adverbial theory of perception. He's correct that this is a possible argument against the case for indirect realism. Personally, my problem with adverbial theories is well expressed by Bonjour:

we seem to have no real understanding of the nature of the states in question or of how exactly they account for the character of immediate experience. It is easy, with a little practice, to construct the adverbial modifiers. But it is doubtful that anyone has a very clear idea of the meaning of such an adverb, of what exactly it says about the character of the state itself — beyond saying merely and unhelpfully that it is such as to somehow account for the specific character of the experience in question.

Dennis also said:

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.

Absolutely correct -- but no direct realist (no contemporary d.r., anyway), would deny that there are mediating processes involved in visual perception. The direct realist's point, to oversimplify greatly, is about the proper use of the word "to see," and, more important, the nature of the real-world relation of seeing. In the primary sense, we see objects, not sense-data or qualia or whatever. (I take it that this is what Dennis means by "inferentially and objectually direct.")

There'a lot more to be said, but I'm going to break this comment off abruptly here in midstream so that I get it posted. More later, maybe.

At 6/02/2008 10:21:00 AM , Blogger Blue Devil Knight said...

Crap. I just wrote a response that got gobbled by blogger. This is a cliffnote version. Dang: the lesson--always copy before hitting 'publish.'

I think that the things people are pointing out (including Feser) shows direct realism (DR) is incorrect. Dreams and hallucinations are enough for me, but there are all sorts of other facts that kill DR too.

However, the epistemic consequences of rejecting DR (a theory of perception) aren't all that obvious. I certainly don't infer that objects are present using premises that include descriptions of sensations. In practice I am usually a direct realist. I think most adults who know things are the same way. Hence, knowledge cannot be a matter of making such inferences, even in adults who are in full knowledge that perception is mediated by neuronal or other processes (the latter for the dualists in the house).

In general, I find the move from rejecting DR to Cartesian foundationalism to be slippery. I agree with the claim C1: We are less likely to be wrong in our beliefs about our conscious states than our beliefs about the world outside of consciousness (though I don't believe this for all conscious states such as emotions (as discussed here in a recent paper by Schwitzgebel), and we do have Anton's syndrome to contend with (blindness denial)).

However, even assuming C1 is true, the move from C1 to Cartesian epistemology is what I don't like. For some, the move seems quite natural, but I think that is because they are implicitly assuming foundationalism is the right road for epistemology to be on.

I prefer to turn the Cartesian's priorities on their head and believe that we can and should explain C1 using science. E.g., a cognitive system set up in such-and-such a way will tend to make judgments about its own representational states that tend to be more immune to error than judgments it makes about the world. This could follow from the simple fact that there are more intermediaries between the world and the consciousness box than there are between sensory systems activated during hallucinations and the consciousness box.

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