Conscious visual perception happens in the frontal lobes

Diagram of the brain with the frontal regions in green and the poster regions in pink

Credit: OpenStax College via Wikipedia

(warning: neuroscience weeds)

Okay, switching back to the other major debate in neuroscience: whether conscious perception happens in the back or front of the brain.  A new study presents evidence that seems to bolster the frontal view: Neural Correlates of the Conscious Perception of Visual Location Lie Outside Visual Cortex (warning: paywall):

When perception differs from the physical stimulus, as it does for visual illusions and binocular rivalry, the opportunity arises to localize where perception emerges in the visual processing hierarchy. Representations prior to that stage differ from the eventual conscious percept even though they provide input to it. Here, we investigate where and how a remarkable misperception of position emerges in the brain. This “double-drift” illusion causes a dramatic mismatch between retinal and perceived location, producing a perceived motion path that can differ from its physical path by 45° or more. The deviations in the perceived trajectory can accumulate over at least a second, whereas other motion-induced position shifts accumulate over 80–100 ms before saturating. Using fMRI and multivariate pattern analysis, we find that the illusory path does not share activity patterns with a matched physical path in any early visual areas. In contrast, a whole-brain searchlight analysis reveals a shared representation in anterior regions of the brain. These higher-order areas would have the longer time constants required to accumulate the small moment-to-moment position offsets that presumably originate in early visual cortical areas and then transform these sensory inputs into a final conscious percept. The dissociation between perception and the activity in early sensory cortex suggests that consciously perceived position does not emerge in what is traditionally regarded as the visual system but instead emerges at a higher level.

Subjects were shown a visual stimulus that led to a perceptual illusion.  But the illusion correlated more with activity in the frontal lobes than in the visual cortex in the back of the brain.  Activity in the visual cortex correlated with the actual visual stimuli rather than the illusion.

And, from the Discussion section of the paper:

Interestingly, the significant cross-classification clusters found in our searchlight analyses were primarily in anterior parts of the brain, such as the lateral prefrontal cortex (LPFC), dACC (the cingulo-opercular control network), and medial prefrontal cortex (MPFC), that are known to be involved in executive control [18, 19, 20, 21, 22] and working-memory-related processing [23, 24, 25, 26]

This seems pretty much in line with predictions from both global workspace (GWT) and higher order theories (HOT) of consciousness.  And it seems like a strike against integrated information (IIT) and local first order theories.  At least if the results hold up.  I imagine the proponents of posterior consciousness theories will be combing through the methodology to see if there are any cracks.

This is actually a stronger result than I would have expected.  I was open to the possibility that conscious visual perception happened in the posterior regions, but that the full package, including associated affects, adding the felt quality of the experience, didn’t get integrated until the information reached the frontal lobes.  But it’s looking like the frontal lobes might have it all as far as conscious perception.

It’ll be interesting to see if the Templeton funded competition comes to the same conclusion, and if not, what differences in the data lead to the discrepancy.  But right now PFC centered theories seem to have a head start.

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44 Responses to Conscious visual perception happens in the frontal lobes

  1. James Cross says:

    I probably shouldn’t comment until I’ve read the whole thing. But…

    “Subjects were shown a visual stimulus that led to a perceptual illusion. But the illusion correlated more with activity in the frontal lobes than in the visual cortex in the back of the brain. Activity in the visual cortex correlated with the actual visual stimuli rather than the illusion.”

    This just seems to suggest that frontal lobes were involved with figuring out the illusion.

    Like

    • The frontal lobes do appear to be involved in the illusion. But if it’s the illusion that is consciously perceived, wouldn’t that mean the processing before figuring out the illusion is pre-conscious?

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      • James Cross says:

        Maybe. I don’t doubt that a good bit of brain activity during conscious states is actually unconscious or preconscious. The problem is how to distinguish which parts of the activity are conscious and which aren’t. I’m not sure we can say everything in the frontal lobes are conscious and everything else isn’t or vice versa. It might be that conscious activity and unconscious activity for an experience are scattered over a lot of the brain.
        If the L5 pyramidal neuron theory has any merit, it might be that those neurons firing in both the frontal lobe and the visual cortex are the NCCs and other neurons firing in those same areas are unconscious or preconscious processing.

        Or it could be that the same activities/circuits have both conscious and unconscious aspects to them and the differentiation is made on some basis other than physical location.

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        • “I’m not sure we can say everything in the frontal lobes are conscious and everything else isn’t or vice versa.”

          We can say definitely say that not everything in the frontal lobes are conscious. The frontal lobes are vast, and a lot of its own processing is preconscious. Isolating conscious awareness to them, even to the specific regions listed in the paper, is just a beginning, assuming the results hold up.

          “If the L5 pyramidal neuron theory has any merit,”

          I think it does, but only as part of the overall framework. Saying consciousness is in the L5s strikes me as implausible. Saying that the networks that are conscious heavily use the L5s seems like a much stronger position.

          Liked by 1 person

          • James Cross says:

            I think the actual theory is that only information passing through the L5 pyramidal neurons is conscious and information on non L5 pyramidal circuits is not conscious , not necessarily that consciousness resides in L5 pyramidal neurons.

            Since consciousness is seemingly unitary but has multiple aspects – sensory integration, internal thoughts, feelings, memories, it would pretty much have to something which integrates multiple parts of the brain.

            Liked by 1 person

          • There are actually multiple levels of integration in the brain. Some people focus on the final integration for action, which happens in the brainstem. But we appear to have no introspective access to processing at this level. There’s also multi-modal sensory integration in the parietal regions, integration for habitual decisions in the basal ganglia, and integration for deliberation in the frontal lobes. It’s this last which we have introspective access to, and I think correlates to what we normally label “consciousness”.

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  2. Wyrd Smythe says:

    Asking where the consciousness resides in the brain seems a bit like asking where the shipness resides in a ship. Given you can apparently operate pretty pretty well with only half your brain, or with large chunks missing, it really seems like a holistic operation.

    In your previous post, in the comments, you wrote how, “About 10% of the axons from the optic nerve actually go directly to the superior colliculus in the midbrain (part of the brainstem).” Which suggests some kind of awareness going on even there. And certainly the PFC seems kind of important.

    The answer to “Where?” seems to be anywhere and everywhere.

    Liked by 2 people

    • James Cross says:

      “anywhere and everywhere”

      Maybe not quite but probably a lot of different places rather than a single location.

      While speaking of axons, what do we make of the apical dendrite in the L5 pyramidal neurons? As I understand it, they run from the lower levels of the cortex (layer 5) to the top of the cortex. There are billions of these lined up side by side. Superficially they resemble tiny antennas. Is it possible these are allowing the neurons to resonate electromagnetically and to sync firings between groups of neurons over wide sections of the brain?

      But maybe my understanding of these structures is wrong.

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    • Certainly most of the brain participates in generating the content of consciousness. But neuroscience has been on a quest in the last few decades to find the neural correlates. In that sense, isolating where a perception becomes a reportable event is a meaningful endeavor. Of course, the regions mentioned in the paper are themselves pretty vast, so even if the results hold up, there’s still a lot of work ahead.

      On the imagery in the midbrain, note that I also said we don’t have introspective access to that imagery. So does it count as awareness? For me, an important point is that the circuitry in the midbrain is reflexive. That means the imagery there isn’t really being examined. It’s like automatic breaking and lane shifting in cars. Something that happens without cognition. That said, for a lot of people, the fact that there is imagery down there makes it a type of consciousness, even if it’s not our consciousness.

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      • James Cross says:

        My working hypothesis is that the main function of consciousness is to integrate information from multiple sources – primarily different senses in more primitive organisms – and make decisions on action.

        The contents of consciousness would be all over the brain but most likely the integration is driven by something evolutionarily older because the requirement for integration would be happen as soon as organisms began developing multiple,more sophisticated senses and a more complex reaction capability.

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        • I’d give the same response I just gave elsewhere on this thread:
          There are actually multiple levels of integration in the brain. Some people focus on the final integration for action, which happens in the brainstem. But we appear to have no introspective access to processing at this level. There’s also multi-modal sensory integration in the parietal regions, integration for habitual decisions in the basal ganglia, and integration for deliberation in the frontal lobes. It’s this last which we have introspective access to, and I think correlates to what we normally label “consciousness”.

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          • James Cross says:

            I think the internal awareness is a focus on multiple parts of the brain which would include the frontal lobe but not be limited to it. The introspective, meta-cognitive aspects of it may originate in the frontal lobes but does not comprise all that is consciousness.

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      • Wyrd Smythe says:

        “On the imagery in the midbrain, note that I also said we don’t have introspective access to that imagery. So does it count as awareness?”

        To the midbrain, certainly. Similar to your car analogy, it might be how an operating system is “aware” of its internal data structures, but applications running on that O/S have no access or knowledge of them.

        I think, perhaps, the bigger problem is that it seems hard to localize “consciousness” when just about every discussion starts with a disclaimer about how no one agrees on a definition for it. How do you find something when you don’t have a clear idea what it is?

        As you say, some see what might be going on in the brainstem as a form of consciousness.

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        • “How do you find something when you don’t have a clear idea what it is?”

          That is the difficulty. I actually think it’s misleading to use the word “consciousness” without qualification. Are we talking about self aware consciousness, primary consciousness, affect consciousness, exteroceptive consciousness, wakefulness, or something else? People sometimes get impatient when I qualify the term. They only want to talk about “real” consciousness, usually the one matching their favorite definition.

          What we can say is that the brainstem doesn’t include the type of consciousness available for self report.

          Liked by 1 person

  3. James Cross says:

    Still assimilating the article, but I’m surprised I see no mention of V5.

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    • Sounds like you’re going through it much more carefully than I did. (I really just skimmed it.)

      From what I can see, they refer to V5 as MT (middle temporal) in the paper.

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      • James Cross says:

        Still not sure what to make of it.

        The claim seems to be: “Consciously perceived location emerges in anterior areas beyond the visual cortex.”

        So it seems limited to location not more broadly.

        Numerous studies seem to suggest NCCs in the visual cortex. A lot of them noted here:

        https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2430003/

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        • James Cross says:

          That study also suggests correlations in the frontal regions too.

          “The most parsimonious account of currently available data is that the current contents of visual consciousness consist of a representation in primary visual cortex and ventral visual pathway corresponding to the attributes represented in consciousness, together with related activity in specific parietal (and perhaps) prefrontal structures.”

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        • I don’t think there’s any doubt that the representations in the visual cortex are a crucial part of the chain. But everything I’ve read implies there has to be later processing on top of it. I think even many posterior consciousness proponents think the parietal regions are crucial. The only question is whether we are ever conscious of it prior to the PFC.

          A lot depends on how we define “consciousness”. If it is outside the scope of introspection (which appears to happen in the PFC), are we conscious of it? Many proponents of the phenomenal vs access consciousness divide would argue that we are. I’m not sure there’s a fact of the matter answer to that question. All we can really ascertain is when it becomes available for self report. (While trying to compensate for the activity related to reporting itself.)

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  4. Lee Roetcisoender says:

    Mike & Eric,
    If you’ve been following my post on Wyrd’s blog, you’ve seen that it can be demonstrated that there is no ontological distinction between mind or matter. Therefore, I postulated that the laws which govern motion and form within the physical world of matter have to be the same laws which govern motion and form within the mental world of mind. Our current methodology for studying mind, and/or consciousness, is grounded in physics. Clearly, that model is the tail wagging the dog simply because the only “thing” we have direct access to is our own experience. And that experience is the only empirically quantifiable evidence which is capable of garnering the evidence needed to determine what those laws actually are. So in conclusion: If one can uncover the mechanisms responsible for motion and form within mind, then those mechanisms can be applied to matter. This method then corresponds to the dog wagging the tail.

    Anybody see a problem with that methodology?

    Like

    • Lee Roetcisoender says:

      James,
      I should have included you on my post……… please feel free to comment, anybody.

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      • James Cross says:

        Regarding motion. I made the comment about V5 not being mentioned. There also isn’t a lot of discussion of MT (middle temporal) either if that is the same.

        My understanding is that motion detection is done in V5 because damage in that area leaves people with an inability to perceive motion. That makes this statement puzzling to me:

        “This “double-drift” illusion causes a dramatic mismatch between retinal and perceived location, producing a perceived motion path that can differ from its physical path by 45° or more.”

        If motion detection is in V5, what would be the involvement of the retina in perceived motion aside from input to V5. It would seem a discrepancy in motion path would be between V5, not the retina, and the frontal lobe. I don’t think the retina per se perceives motion. For that matter, does it even perceive location? I would think it would also be input to other brain processes that create the space illusion/reality.

        “Therefore, I postulated that the laws which govern motion and form within the physical world of matter have to be the same laws which govern motion and form within the mental world of mind.”

        Julian Barbour, who I’ve mentioned before, thinks motion is an illusion. This is part of philosophical tradition going back to Parmenides and Zeno. Hoffman thinks we can derive space-time from the brain (or mind in his world). I’m intrigued by these ideas and occasionally espouse them. The relationship between brain/mind and reality seems more complicated than the simplistic view that brain/mind faithfully reflects reality. But it doesn’t seem quite correct to think it completely manufactures it either.

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        • I do see MT mentioned a lot in the paper (specifically “MT+”). It’s shown in several diagrams. Admittedly, I’ve only skimmed the main experimental sections of the paper, so maybe they don’t give it as much attention as they appear to.

          MT is often used instead of V5 in neuroscience papers, although usually the paper mentions that it’s also V5. This one doesn’t appear to. Indeed, the methodology sections are pretty technical and not calibrated to make things easy for people not deeply enmeshed in the terminology.

          I think the point about the retinal vs perceived mismatch isn’t that the retina perceives anything, merely that the image formed on the retina (and topographically mapped to V1) doesn’t match the consciously perceived perception, wherever that happens.

          “My understanding is that motion detection is done in V5 because damage in that area leaves people with an inability to perceive motion.”

          We have to be careful with this kind of evidence. It indicates that V5 / MT is important for perceiving motion, but not that all motion perception processing happens there. From what I’ve read, the posterior parietal regions are also important for this. And according to this paper at least, so are various frontal regions.

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          • James Cross says:

            “The inability to perceive motion is called akinetopsia and it may be caused by a lesion to cortical area V5 in the extrastriate cortex. Neuropsychological studies of a patient who could not see motion, seeing the world in a series of static “frames” instead, suggested that visual area V5 in humans is homologous to motion processing area MT in primates”

            https://en.wikipedia.org/wiki/Motion_perception

            So V5 or parts of it seem critical to process. I doubt conscious processes take place in single parts of the brain. I think more likely multiple groups of neurons in different parts of the brain are synchronized in some manner to account for the unitary appearance of consciousness. That is why I find the insistence of everything is in the frontal lobe so odd.

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          • When talking about where in the brain conscious perception happens, I do think there is value in being clear what we’re talking about. We’re not talking about a location of a soul, or where the mind in its totality resides. There is no place in the brain like that.

            We can talk about whether information at various stages and locations is part of consciousness, but with the understanding that the pre-conscious stuff is crucial, and that the regions where information enters consciousness could not be conscious by themselves.

            Of course, even talking about whether something is a part of consciousness can get mired in a definitional morass. Does phenomenal consciousness overflow self report? Or is that a coherent idea? Your answer to these questions will determine when you decide that information at a certain point has made it into consciousness.

            I think we can say that information becomes available for self report in the frontal regions. But I suspect it’s possible for information in the parietal and temporal regions, not available for self report, to be captured in memory, and later recalled by the frontal lobes and then be available for self report. In that case, was the initial information part of consciousness? Or is it a part of the nonconsciousness that later bubbled up into consciousness? Is there a fact of the matter answer?

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          • James Cross says:

            I’m inclined to think that all the measures we are using are actually measuring unconscious activity. To use an analogy – the debate is whether the pistons, the driveshaft, the axle, or the wheels are making the car move.

            Liked by 1 person

          • There are parts of a car not involved in producing movement, and some parts that are involved are more crucial than others. The radio, air conditioner, and power seats don’t really contribute to car movement (at least not directly). And if we’re interested in what drives the physical sequence, there’s a lot to be said for examining the motor, always keeping in mind that a motor by itself isn’t going anywhere.

            Similarly, there’s a point in the brain (actually maybe several points) where information becomes available for self report. But those regions by themselves, without all the supporting regions, are not conscious.

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          • James Cross says:

            “several points”

            We are more or less agreeing but I think you are missing the point that consciousness is a holistic property of the brain not just a collection of several points.

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          • Maybe the difference is I’m not satisfied by simply saying that consciousness emerges holistically from the brain. It’s true, it does emerge, but I don’t think we’ve explained anything with that observation. I want to know how it emerges, and I think learning it is achievable.

            I view it similar to how life is emergent from chemistry. The details are messy and complex, but we understand in principle how it works, and are now filling in the details.

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          • Just to clarify, I’m not talking about how life started, which we have yet to figure out, but how it works today in terms of organic chemistry.

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          • James Cross says:

            My gut feeling is that there is something that relates the consciousness problem to the life problem. Of course, there is obvious thing that we don’t suspect we know of anything conscious that isn’t also alive. Yet aside from that my gut tells me there is something more. Certainly the underlying electrochemistry must be mostly the same. Both processes run at the edge of chaos and order. Evolution must be a factor in both. Information is processed. Intelligence accumulates slowly in genes and quickly in brains.

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          • James Cross says:

            I’m hoping to post something soon relating to electromagnetic theories which to me is looking like a much overlooked area of research. It generally seems to be regarded as the province of crackpots so it gets dismissed in favor of the information theories. Yet low frequency EM waves permeate the brain and even the crude detectors we have for measuring them can clearly distinguish basic states like deep sleep, wakefulness, and dreaming.

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          • There is a chance that some ephaptic coupling takes place, but right now it seems pretty slim, particularly in an actual brain where glia insulate the neurons from each other. Low level EM fields do permeate the brain, but they also permeate the environment. If the brain used the actual fields, it would be subject to disruption from those environmental fields. (TMS does affect it, but TMS is relatively strong, and right near the skull.)

            But in the end, it comes down to where the evidence points. If the data pointed toward EM fields, then we would have to investigate. I’d want to know what that EM activity was doing. I don’t think it would rule out information theories, just change the physics of how that information was processed. (That’s also true if, despite everything, quantum physics ever turned out to have a significant role.)

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          • James Cross says:

            I’ve seen those objections. Wait for my post.

            Like

        • Lee Roetcisoender says:

          “Julian Barbour, who I’ve mentioned before, thinks motion is an illusion. This is part of philosophical tradition going back to Parmenides and Zeno. Hoffman thinks we can derive space-time from the brain (or mind in his world).”

          James, as much time as you’ve spent on Bernardo’s blog, I think you recognize that idealism is not tenable. Mind and matter are both reducible to one (1) thing, and to the dismay of the religiously fervent idealists, that one thing is “not” mind. Idealists like to claim Parmenides as one of their champions, but Parmenides was not an idealist. Parmenides is the first person in recorded history to articulate the reality/appearance distinction (RAM). It was an architecture further expounded by Nagarjuna, the Hebrews, Immanuel Kant and now myself.

          According to RAM, reality is contextual all the way down, which include but are not limited to the following: A myriad of intellectual constructions which mind creates. Some of them are accurate depictions of our reality, models which are able to make accurate predictions. Other are delusions and/or creative fictions which are constructed for mere entertainment.

          In conclusion: If one can uncover the mechanisms responsible for motion and form within mind, then those mechanisms can be applied to matter. It’s like Mike articulated, motion is the mind working, and form is the content or the intellectual constructions which the mind constructs. It’s constructions all the way down, and the mechanisms responsible for those constructions be them mental constructions and/or physical constructions has to be the same.

          Peace

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          • James Cross says:

            To be clear. Barbour is not an idealist. Actually he is very much a materialist/physicalist.

            But as far as idealism being tenable, I think it and materialism are functionally equivalent. We have no way to know what the world is composed of outside of our knowing of it. Whether we call it matter or mind it doesn’t matter or mind.

            It may be turtles all the way down. Or it may not…

            Like

    • Lee,
      A lot depends on exactly what you mean by “motion and form with mind”. If you mean the motion and form of the mind working, then yes, I agree.

      But if you mean the perceived or imagined motion and form within the contents of the mind, then I’d say it’s definitely data (empirical data), but not something we can always take a face value, being subject to the limitations of our senses, memory, etc. It is data for our theories, arguably the only data we’ll ever get. But to form scientific theories, the experiences must be repeatable or otherwise verifiable.

      And the only way we can ever judge the resulting theories is by whether they increase the accuracy of our predictions of future empirical observations, and do so better than any alternative theories.

      So, is that agreement?

      Like

  5. Lee Roetcisoender says:

    “So, is that agreement?”

    Absolutely! This corresponds with my hypothesis that mind and matter are intrinsically linked when it comes to causation, an idea that even Wyrd himself was intrigued with.

    Liked by 1 person

    • Wyrd Smythe says:

      “…an idea that even Wyrd himself was intrigued with.”

      For the record, what I said was:

      But what is the difference between the physical causal limits of the “real” world and the often causality-free nature of the mental world? In the same sense I can create a fantasy story or movie, using factual tools, my mind can have wild flights of fancy using a factual brain.

      So I’m not persuaded the the rules of thought apply to the rules of reality. (My dreams, day or night, certainly can get pretty wild.)

      But I am intrigued by the real/mental distinction given I’ve been writing a lot of posts lately about the real/virtual distinction. One might also invoke the factual/fiction distinction with regard to reporting and narrating.

      Simply put, fiction isn’t bound by fact.

      Like

      • Lee Roetcisoender says:

        “But what is the difference between the physical causal limits of the “real” world and the often causality-free nature of the mental world? In the same sense I can create a fantasy story or movie, using factual tools, my mind can have wild flights of fancy using a factual brain.”

        There does not appear to be any limits in either the physical world or the mental world. Now, those fantasy stories, using factual tools are intellectual constructions which are all an expression of mind. And that imaginatively creative mind is an expression of the physical brain. It’s expression all the way down, just like it’s constructions all the way down, constructions which reach the pinnacle of expression, the construction mind.

        So, to correct your error Wyrd, it’s not that there is any causality-free nature of the mental world, because causality “never” fails. It’s just that homosapsens are too dumb to figure out causality period. It’s not our fault…

        Peace

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        • Wyrd Smythe says:

          “There does not appear to be any limits in either the physical world or the mental world.”

          That seems false to me. There are many limits that apply to physical existence, and the posts I’ve been writing are all about how, in contrast, virtual causality is entirely arbitrary (not to mention teleological).

          You say that’s an error, but I haven’t seen anything other than assertions that lets me see exactly how.

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          • Lee Roetcisoender says:

            I can’t argue with that last statement Wyrd. I cannot see your mind. Even if I were physically present and could gaze directly into your physical eyes. All I would have are your assertions.

            Peace

            Like

          • Wyrd Smythe says:

            There is logic, the dialectic, and empirical consistency. As you said in our discussion about the SOM and RAM, even in metaphysics there is (and indeed must be) logic.

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