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Although no one can say with certainty how conscious experience is realized in relation to the brain's activity, all the evidence seems to indicate that it must occur somewhere downstream from the LGN (lateral geniculate nucleus). The reason I say "downstream" is because the optic nerve connecting the retina to the LGN is an afferent nerve through which information is passed in one direction only.

The retina is, of course, an integral part of the overall nervous system, but it's activity seems to be primarily in preparation for sending information to the brain. Within the retina, there is a complex system of intercellular inhibition which seems to be a means of regulating any given cell's response in relation to that of neighboring cells. Another aspect of this preparatory activity is the transformation of graded potentials to action potentials which is analogous to transforming analog signals to digital. This may be a way to minimize errors during the transmission of the signal. In addition to this, the mind distinguishes between neural signals from different sense organs not according to any characteristic of the signals themselves but according to which pathway conveys the signal to the brain. That rules out the possibility that neural signals are somehow transporting phenomenal qualities from the outside world.

In my opinion, all of these physiological facts seem to be more consistent with the sense-data theories which were predominant prior to the 20th century. John Searle is an example of modern philosophy's opposition to sense-data theories. He claims that our conscious experience gives us direct access to the objects of perception (see Intentionality, p.45), but he also makes some assertions which seem to oppose the possibility of such a theory. For example, he recognizes that perceived attributes are distinct from how the "world really is" (Intentionality, p.75). He also acknowledges the causal nature of physiology and even asserts that visual experience occurs within the brain:

"Notice that this story is a causal account, it tells us how the visual experience is caused by the firing of a vast number of neurons in literally millions of synapses. But where, then, is the visual experience in this account? It is right there in the brain where these processes have been going on. That is, the visual experience is caused by the functioning of the brain in response to external optical stimulation of the visual system, but it is also realized in the structure of the brain." (Intentionality, p.267)

If visual experience occurs within the dark recesses of the cranium and has no means to access the world as it is upstream from the LGN, it's difficult to imagine in what sense we can be said to have a direct access to the objects of perception. Michael Tye is another philosopher opposed to sense-data theory, and according to his account, consciousness is "transparent". Of course, he gives no physiological explanation how that might be possible.

My question is: Among the philosophers who make similar claims, such as to having direct access to the objects of perception or that consciousness is transparent, are there any that have attempted to explain that in physiological terms?

2 Answers2

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Searle isn't contradicting himself. We need to distinguish the content of an experience from the nature of the experience itself. Direct realism is a thesis about the content; the bit in the section you've quoted looks to be about the nature of the experience.

Direct realists say the content of my thought of the tree outside my window is the tree itself. This is in contrast to sense-datum theorists who say that the content of my thought is not the tree itself, but merely my mental representation of the tree.

However, saying that the content of my thought is the tree, isn't yet to have said anything at all about the ontology of the thought that has the tree as its content. What is this thing the thought? That's what Searle is answering in the bit you've quoted. "The visual experience" is the name, Searle is saying, of the whole complicated process of environmental interaction between the tree, light, and the extraordinarily complicated organization of my nervous system. I think he's making the point that these complicated physiological cum environmental changes constitute the experience, rather than cause it. Just like each of the buildings on campus constitute the university, but none of the buildings is the cause of the university.

  • Thanks for the answer. Howard Robinson says, "[Descartes] makes it quite clear that ideas possess what he calls 'objective reality', which means that it is part of their essential nature to have an object—that is, to be of something. This contradicts [the conception] that sense-contents possess no intrinsic intentionality." This suggests that intentionalists should agree with the sense-data theorists with respect to content and perhaps with respect to the ontology of the experience as well. Is there no real debate then? Is it just a question of terminology and emphasis? –  Mar 30 '16 at 19:54
  • That's an excellent question. Where is the reference to Robinson? I would usually think of Hume rather than Descartes as an example of a sense-datum theorist, but I'm not an expert on the matter. Certainly, the difference between direct realists and sense datum theorists is supposed to be that sense-datum theorists suffer the "no good inference" problem, i.e. that they can't be certain that their mental representations correspond to the world, whereas the direct realists aren't supposed to have that problem. Robinson might be arguing that that isn't right though, I'd have to check. –  Mar 30 '16 at 19:58
  • Page 11 of Perception. But Robinson aside, the "no good inference" problem always struck me as rather superficial, because even before encountering Robinson, I never imagined that sense-data philosophers ever imagined it to be anything else but intentional. –  Mar 30 '16 at 20:03
  • Let me take a look, and if I'll see if I can get back to you in a few days. I've not read Perception, but I don't think Robinson would be too worried about the problem anyway, since he's an idealist. There's no need to make an inference, hence no need to worry about whether the inference is a good one or not! –  Mar 30 '16 at 20:08
  • If the content of perception is the thing in itself as you, how does it make sense for Searle to speak of phenomenal properties which don't belong to it? To what could those properties belong except to a mental image representing the object perceived? But he expressly rejects that idea. Unless Searle and everyone else is essentially a sense-data theorist with a possible emphasis on intentionality, I'm still looking for a physiological account for the opposing view. –  Mar 31 '16 at 01:21
  • Searle's definitely not a sense-datum theorist. The SEP article attributes to Searle the view that "some physical qualities or states are irreducibly subjective entities". I'd take it that the physical state in question here is the brain state. So "what it's like to see red" is subjective, and it's a property that my brain state (as opposed to some mental representation) is supposed to have. –  Mar 31 '16 at 13:08
  • http://plato.stanford.edu/entries/qualia/#Repqualia there's some nice material on transparency in there too, that appears relevant. –  Mar 31 '16 at 13:08
  • I know that Searle say he's not a sense-data theorist; he just talks like a one. What distinction can be made between a brain-state that appears red and a sense datum that appears red? And if phenomenal red is not a known property of of gray matter, on what basis can it be asserted that it belongs to the brain? My question wasn't about Searle. Unless everyone agrees that phenomenology is a property of sense-data or pseudo-brain states, I'm still looking for a physiological explanation. –  Mar 31 '16 at 14:36
  • This is me extrapolating, so take it with a grain of salt. But, I think Searle would deny your premise that "what it's like to feel" red isn't a known property of grey matter. Wouldn't he simply rather reject your claim that there should be a physiological explanation? I think he'd say your demand for an explanation is misplaced. You need physiological explanations of physiological phenomena, sure. But qualia aren't physiological phenomena in that sense, so why would there be a physiological explanation of them? Now it might be that Searle's wrong here. (Dennett would certainly say so!) –  Mar 31 '16 at 14:48
  • It's not my premise. It was you who said, "it's a property that my brain state." My question has to do with the idea of accessing the properties that belong to the external world either directly or transparently. I'm not convinced that no one holds such a view, so I would like a a physiological explanation for those who do. –  Mar 31 '16 at 15:08
  • I'm not clear what it is that you want an explanation of. Do you want a physiological explanation of visual experience? Do you want a physiological explanation of how an experience has content? Do you want a physiological explanation how an experience has a subjective, qualitative character? Those are all quite different questions and I can't see why we would even expect there to be a physiological explanation of the last two. But that's all I have to contribute, so I'll wait now for someone more knowledgeable to come along. –  Mar 31 '16 at 15:20
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Many current theories of perception http://theconversation.com/how-do-our-brains-reconstruct-the-visual-world-49276 shape it more as the Ancient Greeks did than the way Newtonian physics does. Something goes out from the mind and meets reality rather than coming into the mind and getting encoded. Of course, we know the light comes to us, but the idea of what is to be seen seems to meet it halfway, in the brain, as the visual field is being turned into information. The same seems to be true of all the senses to some degree.

Optical illusions and related Apophenias tell us that the originating assumption of what we are going to see has more reality for us than the actual input:

  • We see faces and snakes where they clearly are not present.
  • We notice dogs in clouds (not tables).
  • We hear the exact same sound pattern as different phonemes in different contexts.
  • Colors seem to spread into white space.
  • The mp3 process discards information and we cannot hear the difference it, but if they discard a little too much, we don't hear a lack of something, but totally unrelated (schwooshing) patterns invade the sound as a whole.
  • We miss doubled words when reading, and may have a hard time seeing them even when they are pointed out.

It seems obvious that we project our intentions on the data well before it reaches the point of really thinking. All this error is explained by the success it enables. By being a little too aggressive with our assumptions, we can see things we are looking for faster than we can ordinarily interpret them. It is common for some reaction times to be shorter than would be possible if the brain were to fully interpret the input.

Sensory content is clearly afferent, but we do not passively receive information. In fact, unexpected information can fail to register. For many, that means the best theory is that the brain is reaching out into its pool of data to confirm suspicions about what is present. It is not simply observing the patterns that are present and deducing the layout of the world. If there is no suspicion, we may fail to perceive the otherwise obvious. Change blindness seems to be quite the norm.

This implies that the ideas of things that are to be checked for may originate in the mind and then get shaped by testing against the outside world, instead of getting incorporated from sense-data. They are sculpted rather than molded or drawn. Inappropriate assumptions are made and then removed when they are found not to fit into the model we are testing against.

In that sense, you can say that reaction timing and eye tracking physiology supports the idea that sensory impressions and interpretations are not built up from the data, but originate in the mind, and must be more available to it than sensory data.

  • Thanks for the answer, but I don't know what it has to do with what I was asking. –  Mar 31 '16 at 00:56
  • If the objects of perception are internal objects projected onto reality, rather than external objects internalized from reality then the mind has direct access to them. –  Mar 31 '16 at 18:29
  • Via reaction timing, and in certain other cases we can trace this happening in physiology -- we start the reaction when we establish the expectation and not after we have the perception, then we subvert it if the expectation fails. So it is the expectation, which is fully accessible to the mind, that is the real object of perception. –  Mar 31 '16 at 18:39
  • I don't disagree with that. However, it looks like Searle was a poor example for me to have chosen, because I was trying to give an example of somebody who believes that we have a direct access to external objects--if any such philosopher exist. The idea that the mind has direct access to internal object seems to be indistinguishable from the sense-data theories. –  Mar 31 '16 at 18:55
  • You asked "Among the philosophers who make similar claims, such as to having direct access to the objects of perception or that consciousness is transparent, are there any that have attempted to explain that in physiological terms?" The answer is yes, if you listen to what they actually mean by those statements. If you purposely misunderstand them, then no. Not even Plato, Leibniz or Berkeley imply the mind has access to anything but ideas. The question is whether the idea comes first and seeks the object, or sense data accumulate and create the idea. –  Apr 04 '16 at 06:28
  • Take Plato -- the notion of something like a tree comes, for him, out of the ideal realm into the mind and is projected out the eyes to find imperfect imitations of itself in external reality, which the mind then uses to adapt its local notion of what a tree is. That is the original source that gave us the vocabulary about which you are asking in the West. The alternative is that there is no notion of a tree until we see one and decide the various images of branching things must have something in common. Some phobias, reaction times, apophenia, etc support Plato better than the alternative. –  Apr 04 '16 at 06:47
  • (Of course, in a modern scientific world, we may need to base this source of 'ideals' in genetics or some other shared pool of instincts, rather that in the mind of God.) –  Apr 04 '16 at 06:51
  • In spite of what you assume, I have no reason to intentionally misrepresent anyone. Furthermore, I question your interpretation of the sense-data theory. According to your understanding of it, ideas are "incorporated from sense-data." I believe that's simply untrue. And for the record, ideals don't originate from gene pools; the Bible clearly teaches that they originate from God. Kant also argued persuasively that an empirical origin would deprive them of any necessity or universality, hence the absurdity of materialism. –  Apr 04 '16 at 10:03
  • For the record: 1) I won't take the Bible as evidence when discussing philosophy or science -- It gives you lots of reasons to misrepresent everyone. And that makes the first sentence of your last comment into a lie. 2) If you consider materialism absurd, why ask about physiology? 3) There is no philosopher who thinks the mind has direct access to the same things we sense, it is not just Searle you have mischaracterized, it is the whole history back to Plato. Intentional or not, you did not respond to @shane's correction by taking correction. So your point is lost. –  Apr 04 '16 at 14:03
  • Are you confusing materialism with science? And I have no I idea what you're talking about concerning shane's correction. –  Apr 04 '16 at 14:13
  • Let's start over. For me the distinction is 1) Sense data theory: There is unclassified sense data that exists in the mind and represents current reality and is then classified into 'real ideas'. vs 2) Plato to Searle: Perception is an active process which selects from reality and classifies, with no intermediate "sense data" per se. My argument: if 1 were true we could not begin to react before collecting the data. But we do. We could also carefully reprocess the data to retroactively remove illusions. But we don't. Can we stick to the answer? –  Apr 04 '16 at 15:01
  • To your last remark: If God working via genetics is absurd, then so is God working via physiology. You cannot "sort of reject science, but not really." If ideal images reach us, they do so through some process, and that process probably has a physical trace. So whether or not they originate with God, ideals will also have materialist explanations. –  Apr 04 '16 at 16:19
  • The phobia of snakes or of maggot-like patterns (as in trypophobia) seems to clearly indicate an abstract idea that is inherited for biological reasons. A certain segment of the population automatically recognizes these, and is scared or disgusted, even at ages where they have never encountered them in real life. So there are at least a few good examples not traceable directly to God. –  Apr 04 '16 at 16:38
  • I'm quite certain that God does work through genetics, but that wasn't the question. You denied God as the author of ideals and put genetics in His place, and putting the creature in place of the Creator is by definition idolatry. You may believe that I'm morally obligated to treat that as if it were no big deal, but I believe that you're better off knowing the truth. –  Apr 04 '16 at 16:44
  • If you can, please put pushing other peoples' belief systems around pointlessly aside. Please focus on the answer, and decide if you still find it off-topic. I am trying to cosset your mythology without taking being called absurd personally. I don't intend to respond to your questions in the future. –  Apr 04 '16 at 17:16
  • Having asked for you to focus there, further commentary on anything else will also not be welcome. –  Apr 04 '16 at 17:21
  • And for the record, if you choose to be offended by statements about what we may need to do, a framing that offers only flexibility and does not place any requirement upon your beliefs whatsoever, and you are willing to tell me what I am supposed to believe, you are far too defensive to be worth interacting with. Besides which, the Bible says no such thing. Aside from oblique references to our being in God's image it offers no real insight into how the mind works, and makes no effort to even try. Try reading it instead of imputing contents to it at random. –  Apr 04 '16 at 21:41
  • I'm not offended. You're the one that brought God into the discussion, so if you want to change the subject, that's fine with me. I just have other things to think about right now. –  Apr 04 '16 at 21:42
  • That was meant to be God, a la Plato/Berkeley. The Bible still says nothing about how perception or the transfer of ideas works. So, lying will get you told you are lying. –  Apr 04 '16 at 21:44
  • I surely do not want more contact, if I can't even get straight answers here. –  Apr 04 '16 at 21:57
  • I couldn't tell by the way you keep posting comments. :-) –  Apr 04 '16 at 21:58