Philosophy Discussion Forums | A Humans-Only Club for Open-Minded Discussion & Debate

[Consul]

Humans do not, for instance, run their consciousness at lower levels, to be equivalent to, say, that of an insect or a flatworm. It's either a full human kaleidoscope of consciousness or "nothing". I question that "nothing", just as cosmologists questioned whether space was a true vacuum. I think that, just as there are organisms humans cannot see with the naked eye, that reflexes are themselves "micro-consciousness", too subtle to qualify as consciousness in our conceptualisations.

No, once again, responsiveness to stimuli just isn't the same as phenomenal consciousness!

[Consul]

A very interesting question: Do "humans and other animals share minds of the same general sort with the same overall architecture"?

QUOTE>
"Everyone allows that there is some sort of significant discontinuity between human and animal minds. Only humans contemplate the origins of the universe, the possibility of life after death, and the nature of right and wrong. Only humans build complex multipart tools, make kayaks, and hunt with weapons. And of course only humans perform exact mathematical calculations, conduct scientific experiments, and evaluate the strength of an argument for a conclusion. These and other differences have enabled us ultimately to travel to the moon, to construct skyscrapers and the internet, and (unfortunately) to alter the climate of the planet itself.

It is tempting to think that a behavioral discontinuity of this magnitude is best explained by some equally radical mental discontinuity. Humans must have a different kind of mind from the minds of other animals, one might think. The most extreme form of discontinuity-view is to deny that animals have minds at all, as René Descartes famously did. If this were correct, then it would settle our question about phenomenal consciousness in animals quite straightforwardly. If animals lack mental states altogether, then plainly they can’t possess phenomenally conscious mental states.

While no one accepts the Cartesian view any longer, there are still plenty of defenders of mental discontinuity. I shall consider two such proposals in the course of this chapter. One is to deny that animals are capable of genuine thought, while allowing that they enjoy mental states of other kinds. The other is to claim that the human mind comprises two systems for thinking, reasoning, and decision-making, only one of which is shared with other animals. I shall suggest that neither view is defensible. The upshot is that the human mind is strongly continuous with the minds of nonhuman animals. But, as we will see in due course, this by no means settles the question of phenomenal consciousness in animals.

On the view that I favor, humans and other animals share minds of the same general sort with the same overall architecture (…). But humans have a number of distinctive adaptations. Some of these have to do with sources of motivation (especially of a prosocial sort), while others facilitate learning in particular domains (notably language and other forms of social cognition). The result is that humans collaborate and learn from others while living together in large groups of unrelated individuals, and with successful innovations in culture, technology, and thought being retained and transmitted across the generations, gradually “ratcheting up” overall human capacities."

(Carruthers, Peter. Human and Animal Minds: The Consciousness Questions Laid to Rest. New York: Oxford University Press, 2019. pp. 29-30)
<QUOTE

[Consul]

Carruthers argues that…

QUOTE>
"The human mind is fully continuous with the minds of nonhuman animals, I suggest. Most other animals are capable of compositionally structured thought, and have minds organized around a central workspace (working memory). In the course of our evolution we surely acquired some additional mental capacities, such as language. And we greatly extended the sophistication and scope of others (such as executive function). But one major source of the vast behavioral differences we noted at the outset is cultural. It is our status as cultural beings, not our possession of a radically distinct kind of mind, that explains why our achievements far surpass those of other animals (Henrich 2016). None of this entails that animals are capable of having phenomenally conscious mental states, however. Cognitive organization is one thing; phenomenally conscious qualities may be quite another."

(Carruthers, Peter. Human and Animal Minds: The Consciousness Questions Laid to Rest. New York: Oxford University Press, 2019. p. 51)
<QUOTE

[Consul]

QUOTE>
"The human mind is fully continuous with the minds of nonhuman animals, I suggest. Most other animals are capable of compositionally structured thought…Cognitive organization is one thing; phenomenally conscious qualities may be quite another."

(Carruthers, Peter. Human and Animal Minds: The Consciousness Questions Laid to Rest. New York: Oxford University Press, 2019. p. 51)
<QUOTE

The problem I have with this is that I disbelieve in (phenomenally) nonconscious thought. I believe thinking is always a (phenomenally) conscious, experiential process; so no animal is a thinker unless it is a subject of experience. For example, Fodor's term "language of thought" doesn't refer to conscious inner speech, but to nonconscious mental processes (manipulations of mental representations). There may be nonconscious sign processing in minds/brains, but it isn't properly called thinking unless it takes place in the form of conscious inner speech or, more generally, consists in the conscious use of linguistic or nonlinguistic imagery (for certain intellectual purposes, e.g. reasoning, planning).

[NickGaspar]

We can not say about ... Atlas "filters".

How do you even come up with these things? I never said or implied anything about some "filters".

I am really sorry. I thought you wrote: "There are new upcoming consciousness theories named 'filter' or 'reducing valve' theory of mind
(2019) Consciousness is a property of the Universe that is filtered by the brain".
But if you did and it's just a problem with the Ctrl+C CTRL+P of my keyboard....I am terrible sorry.

Do you have trouble reading names? Did you mean ctrl+v?

Anyway, "filter" theories are for kids, just as "generate" theories are.

ok!

[Sy Borg]

I am not sure that Robocop would have felt any more than the ED-209 (the security droids), just that he would have had more sensitive sensing equipment. At what point is a conscious system complete? Just the brain, or even just the cortex, with "black boxed" inputs? Do we need the spine? Sensory nerves and motor nerves? How many of the original peripheral nerves would be needed?

The brain or CNS (brain + spinal cord) isn't physiologically self-sufficient, so it needs to be connected to and integrated into a natural or artificial body of some kind or other. However, again, there's a distinction between a factory and a supply firm. The former depends on and interacts with the latter, but the latter isn't part of the former. That the brain isn't itself an independent organism doesn't mean that it isn't the (only) factory of consciousness, the (only) place in the body or organism "where the magic happens."

Maybe, but I do not have the same faith as others that the conceptions of 2021 will stand up in fifty years' time. I see too many basic gaps in our knowledge, as already discussed ad nauseam.

Also, I am confident that structures will be found that fulfil the same functions as brains. In historical terms, researches have only recently discovered that birds have far complex mentalities than assumed. The assumption was based on birds' lack of a cerebral cortex, thought to the be exclusive organ of higher order brain functions. Then it was found that the pallium in a bird's brain functioned in an equivalent way as a cerebral cortex in mammals.

Thus, if an organism can senses, then any claim that they do, or do not, experience their lives is speculative. There is still much that is unknown about how microbes achieve the complex things they do. It's easy to dismiss them as "biological machines" because there is no cost to us to dismiss the consciousness of less powerful beings. I am not suggesting high level cognition in them, more likely vague sensations.

None of us know for sure, but if I had no choice but to bet my worldly goods on what future researchers will determine about consciousness, I'd say that life and qualia are synonymous. That to be alive is to feel something.

I see no justification for biopanpsychism/panbiopsychism (the view that all living beings are feeling, i.e. subjectively experiencing, beings). Where and how does the "magic" of sentience happen in an organism lacking a (central) nervous system?

As above, there may be other structures that perform equivalent functions, albeit far more simply.

Humans and higher order animals (with some exceptions) tend to have on/off consciousness, in that we are either experiencing highly sophisticated consciousness (compared with other animals) or we are unconscious.

Humans do not, for instance, run their consciousness at lower levels, to be equivalent to, say, that of an insect or a flatworm. It's either a full human kaleidoscope of consciousness or "nothing". I question that "nothing", just as cosmologists questioned whether space was a true vacuum. I think that, just as there are organisms humans cannot see with the naked eye, that reflexes are themselves "micro-consciousness", too subtle to qualify as consciousness in our conceptualisations.

That's a straw man, because "highly sophisticated consciousness" isn't the only level of human consciousness. There are several levels of human (self-)consciousness or (self-)awareness, and several degrees of human wakefulness or alertness (ranging from vigilance to somnolence). For example, concerning their cognitive or intellectual (self-)awareness, human persons suffering from dementia do "run their consciousness at lower levels", but they are still phenomenally conscious.

As for the content of human consciousness, the number of (kinds of) experiences occurring therein simultaneously is variable. It's not always the "full human kaleidoscope" of humanly possible experiences. (Imagine floating in a sensory-deprivation tank!)

Obviously we cannot compare the consciousness of a tired, senile human with that of, say, P. pacificus, right? If you are tripping out in a sensory deprivation tank, would you equate that level of sentience with, say, a tardigrade's?

No matter how sleepy or damaged a human mind, it's still be akin to comparing a mountain with a pebble. In that, you have illustrated my point.

That is, it is impossible for humans to imagine what it would feel like to be a much simpler organism. Their tiny, inconsistent and indistinct levels of awareness and sensation would seem like nothing to us. We don't know how far back in the evolutionary timescale that sensations emerged.

[Consul]

Also, I am confident that structures will be found that fulfil the same functions as brains.

I don't think so, because the anatomies of (C)NS-less organisms are well known; so if there were such functionally equivalent non-neuronal structures, the scientists would have found them already. (Let me stress again that the term "plant neurobiology" is a misnomer!)

In historical terms, researches have only recently discovered that birds have far complex mentalities than assumed. The assumption was based on birds' lack of a cerebral cortex, thought to the be exclusive organ of higher order brain functions. Then it was found that the pallium in a bird's brain functioned in an equivalent way as a cerebral cortex in mammals.

Whatever kind of (conscious) mind they have, birds do have brains. Nonhuman animals needn't have a humanlike brain in order to have a (conscious) mind, but they must have some kind of brain or other. For example, octopus brains are very different from human brains, but they are brains all the same.

Thus, if an organism can senses, then any claim that they do, or do not, experience their lives is speculative. There is still much that is unknown about how microbes achieve the complex things they do. It's easy to dismiss them as "biological machines" because there is no cost to us to dismiss the consciousness of less powerful beings. I am not suggesting high level cognition in them, more likely vague sensations.

It is not the case that in the realm of speculation all hypotheses are equally (im)plausible or (im)probable. The hypothesis that nervous systems and especially central ones are necessary for conscious minds appears highly plausible and probable in the light of our scientific knowledge of nature, and there is no convincing evidence for its negation!

I think any form of phenomenal consciousness (subjective experience) is integrated into and dependent on a mind qua cognitive system.

By the way, we humans have "vague sensations" too. What makes us special and even unique (on Earth) is our reflective self-consciousness: We have the cognitive capacity for linguistic thought about our conscious minds, which all nonhuman animals (on Earth) lack.

I see no justification for biopanpsychism/panbiopsychism (the view that all living beings are feeling, i.e. subjectively experiencing, beings). Where and how does the "magic" of sentience happen in an organism lacking a (central) nervous system?

As above, there may be other structures that perform equivalent functions, albeit far more simply.

Even if organisms lacking a nervous system can properly be said to have a mind in the sense of having some mental (cognitive) abilities and states (*, there is no good reason to suppose that they also have phenomenal consciousness.
(* It's partly a matter of semantics, i.e. how psychological concepts such as <mind> are defined.)

Obviously we cannot compare the consciousness of a tired, senile human with that of, say, P. pacificus, right? If you are tripping out in a sensory deprivation tank, would you equate that level of sentience with, say, a tardigrade's?

There are levels of (intransitive and transitive) consciousness in the sense of levels of awakeness or alertness, or of awareness (perception, cognition) of oneself or one's environment, and there are levels of intelligence; but what is a "level of sentience"?

No matter how sleepy or damaged a human mind, it's still be akin to comparing a mountain with a pebble. In that, you have illustrated my point.

What exactly is compared with what here? For example, the level of consciousness qua degree of wakefulness of a vigilant dog is surely higher than that of a somnolent human. And isn't the healthy mind of an adult chimp on a higher level of consciousness qua degree of (self-)cognition or (self-)perception than the mind of a human suffering from dementia?

That is, it is impossible for humans to imagine what it would feel like to be a much simpler organism. Their tiny, inconsistent and indistinct levels of awareness and sensation would seem like nothing to us. We don't know how far back in the evolutionary timescale that sensations emerged.

Any attempt at an empathetic imagination of nonhuman minds from the first-person perspective contorts their reality insofar as it is done with and takes places within our human minds. So when I try to imagine what it's like to be a cat with a cat mind, I inevitably end up imagining something else, namely what it's like to be a cat with a human mind, which is surely unlike what it's like to be a cat with a cat mind.

However, it doesn't follow that a comparative psychology of human and nonhuman minds or consciousnesses is impossible in principle, just because we cannot have any introspective access to nonhuman minds or consciousnesses.

[Sy Borg]

Also, I am confident that structures will be found that fulfil the same functions as brains.

I don't think so, because the anatomies of (C)NS-less organisms are well known; so if there were such functionally equivalent non-neuronal structures, the scientists would have found them already.

That is only an assumption, and not of the kind that tends to play out well in history.

In historical terms, researches have only recently discovered that birds have far complex mentalities than assumed. The assumption was based on birds' lack of a cerebral cortex, thought to the be exclusive organ of higher order brain functions. Then it was found that the pallium in a bird's brain functioned in an equivalent way as a cerebral cortex in mammals.

Whatever kind of (conscious) mind they have, birds do have brains. Nonhuman animals needn't have a humanlike brain in order to have a (conscious) mind, but they must have some kind of brain or other. For example, octopus brains are very different from human brains, but they are brains all the same.

Nonetheless, the assumption was made that they lacked higher mental functions due to their lack of a cortex. They knew about the pallium, but not about some of its functions in bird brains.

By the same token, other equivalences may be found in other organisms. The octopus's non-centralised brains alert us to the fact that configurations of consciousness-shaping organs can be unexpectedly different.

Thus, if an organism can senses, then any claim that they do, or do not, experience their lives is speculative. There is still much that is unknown about how microbes achieve the complex things they do. It's easy to dismiss them as "biological machines" because there is no cost to us to dismiss the consciousness of less powerful beings. I am not suggesting high level cognition in them, more likely vague sensations.

It is not the case that in the realm of speculation all hypotheses are equally (im)plausible or (im)probable. The hypothesis that nervous systems and especially central ones are necessary for conscious minds appears highly plausible and probable in the light of our scientific knowledge of nature, and there is no convincing evidence for its negation!

Yes, there's plenty of convincing circumstances for its negation - unexpected complexity and flexibility in the behaviours of non-brained organisms. It's not evidence, but it's real and often dismissed without investigation based on brain-based dogmas.

I see no justification for biopanpsychism/panbiopsychism (the view that all living beings are feeling, i.e. subjectively experiencing, beings). Where and how does the "magic" of sentience happen in an organism lacking a (central) nervous system?

As above, there may be other structures that perform equivalent functions, albeit far more simply.[/quote]

Even if organisms lacking a nervous system can properly be said to have a mind in the sense of having some mental (cognitive) abilities and states (*, there is no good reason to suppose that they also have phenomenal consciousness.
(* It's partly a matter of semantics, i.e. how psychological concepts such as <mind> are defined.)[/quote]
It would be very basic, but it may well feel like something to be a microbe - or certain microbes (who knows?).

Obviously we cannot compare the consciousness of a tired, senile human with that of, say, P. pacificus, right? If you are tripping out in a sensory deprivation tank, would you equate that level of sentience with, say, a tardigrade's?

There are levels of (intransitive and transitive) consciousness in the sense of levels of awakeness or alertness, or of awareness (perception, cognition) of oneself or one's environment, and there are levels of intelligence; but what is a "level of sentience"?

To experience the same kind consciousness as a tardigrade - to know what it feels like to be a tardigrade. My argument is that, to us, feeling like a tardigrade would feel like nothing, like deep sleep, but such feelings would be significant to tardigrades.

No matter how sleepy or damaged a human mind, it's still be akin to comparing a mountain with a pebble. In that, you have illustrated my point.

What exactly is compared with what here? For example, the level of consciousness qua degree of wakefulness of a vigilant dog is surely higher than that of a somnolent human. And isn't the healthy mind of an adult chimp on a higher level of consciousness qua degree of (self-)cognition or (self-)perception than the mind of a human suffering from dementia?

I am saying that humans would be unable to perceive the simplest consciousnesses. They are too trivial as compared with our deeply complex psyches. We humans have long been dismissive of other organisms' capacity to feel and, while much improvement in this area his happened in the last century, it appears to me that we just lowered the bar, while remaining gatekeepers - of anthropocentric conceptions of what it feels like to be alive. It's hard not to be anthropocentric because it's all we have. There are still many researchers who believe that insects have no phenomenal consciousness - that being an insect does not feel like anything.

I am aware that you have a more nuanced view on this, and draw the line somewhere around brained nematodes. I am not convinced that we have solved as much of this puzzle as you are.

That is, it is impossible for humans to imagine what it would feel like to be a much simpler organism. Their tiny, inconsistent and indistinct levels of awareness and sensation would seem like nothing to us. We don't know how far back in the evolutionary timescale that sensations emerged.

Any attempt at an empathetic imagination of nonhuman minds from the first-person perspective contorts their reality insofar as it is done with and takes places within our human minds. So when I try to imagine what it's like to be a cat with a cat mind, I inevitably end up imagining something else, namely what it's like to be a cat with a human mind, which is surely unlike what it's like to be a cat with a cat mind.

However, it doesn't follow that a comparative psychology of human and nonhuman minds or consciousnesses is impossible in principle, just because we cannot have any introspective access to nonhuman minds or consciousnesses.

When I conduct the thought experiment I think of blind pulses within, like breaths or heartbeats, and tingling on the outside where the environment is sensed. There is no emotion, no care. Just sensations, attraction and repulsion, excitation and slowing. We call such things "biological machines" but that's just an analogy because they are obviously not machines - they are simple living, sensing beings.

[NickGaspar]

Is It Time to Give Up on Consciousness as ‘the Ghost in the Machine’?
https://neurosciencenews.com/consciousn ... ine-18566/

Yesterday neurosciencenews published an article on this old debate and explained why the available science doesn't leave any room for ghost stories any more.

[Consul]

Is It Time to Give Up on Consciousness as ‘the Ghost in the Machine’?
https://neurosciencenews.com/consciousn ... ine-18566/

Yesterday neurosciencenews published an article on this old debate and explained why the available science doesn't leave any room for ghost stories any more.

Interesting, thanks! Here's the paper mentioned:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8121175/

[Consul]

Interesting, thanks! Here's the paper mentioned:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8121175/

The authors endorse and defend epiphenomenalism about conscious events/states:

"Although we readily accept the first-person reality of personal experience, we aver a uni-directional causal relationship, whereby neurological states (somehow) generate mental states, but that these mental states (derived from physical states) that we become aware of, do not have the capacity to influence physical or mental states."

To quote myself from a previous post:

"There is a distinction between a causal mechanism that is different from what it causes, and a compositional/constitutional mechanism that is identical with what it is a mechanism of. Reductionists are looking for the latter!"

The authors of that paper speak of causal neural mechanisms of consciousness. But according to the view I endorse—mereological physicalism, compositional/constitutional materialism—, consciousness isn't "vertically" caused by (and thus different from) neural mechanisms, because it is composed of or constituted by those mechanisms instead. This is a version of the mind-brain identity theory, because a constitutive, noncausal mechanism of something is identical with what it is a mechanism of. If constitutional materialism about conscious ocurrents is true, the general question is whether mechanisms consisting of non-epiphenomenal parts can constitute epiphenomenal wholes and thus be epiphenomenal as wholes. If all parts of a whole are non-epiphenomenal, how can the whole be epiphenomenal? – I'm not sure a consistent epiphenomenalistic mereological physicalism about phenomenal consciousness is possible.

[Consul]

Is It Time to Give Up on Consciousness as ‘the Ghost in the Machine’?…

If a subjective experience is nothing but "a passive accompaniment to neurocognitive processes" (the authors of that paper), isn't phenomenal consciousness still a "ghost in the machine"?

[Consul]

I don't think so, because the anatomies of (C)NS-less organisms are well known; so if there were such functionally equivalent non-neuronal structures, the scientists would have found them already.

That is only an assumption, and not of the kind that tends to play out well in history.

No, since if "the anatomies of (C)NS-less organisms are well known"—which is true!—, there are no hidden, hitherto undiscovered organs or systems "that fulfil the same functions as brains."

Whatever kind of (conscious) mind they have, birds do have brains. Nonhuman animals needn't have a humanlike brain in order to have a (conscious) mind, but they must have some kind of brain or other. For example, octopus brains are very different from human brains, but they are brains all the same.

Nonetheless, the assumption was made that they lacked higher mental functions due to their lack of a cortex. They knew about the pallium, but not about some of its functions in bird brains.

Being wrong about the capacities of nonhuman minds doesn't mean being wrong about the necessity for brains.

By the same token, other equivalences may be found in other organisms. The octopus's non-centralised brains alert us to the fact that configurations of consciousness-shaping organs can be unexpectedly different.

An octopus does have a central(ized) nervous system!
Brains come in various sizes and shapes, but there are no brainlike nonbrains in organisms that are functionally and informationally equivalent to brains.

It is not the case that in the realm of speculation all hypotheses are equally (im)plausible or (im)probable. The hypothesis that nervous systems and especially central ones are necessary for conscious minds appears highly plausible and probable in the light of our scientific knowledge of nature, and there is no convincing evidence for its negation!

Yes, there's plenty of convincing circumstances for its negation - unexpected complexity and flexibility in the behaviours of non-brained organisms. It's not evidence, but it's real and often dismissed without investigation based on brain-based dogmas.

No, there isn't! There's just plenty of unjustified conclusions. For if complex and flexible forms of behavior are brain-independent, it by no means follows that phenomenal consciousness is brain-independent too.

"Most researchers accept that even quite complex perception, cognition, and control of action can go on entirely 'in the dark'."

(Godfrey-Smith, Peter. "The Evolution of Consciousness in Phylogenetic Context." In The Routledge Handbook of Philosophy of Animal Minds, edited by Kristin Andrews and Jacob Beck, 216-226. London: Routledge, 2018. p. 220)

It would be very basic, but it may well feel like something to be a microbe - or certain microbes (who knows?).

"May" in the sense of "logically possible", yes; but given what we know about the morphology and physiology of bacteria and protozoa (unicellular microorganisms), it is extremely improbable.

There are levels of (intransitive and transitive) consciousness in the sense of levels of awakeness or alertness, or of awareness (perception, cognition) of oneself or one's environment, and there are levels of intelligence; but what is a "level of sentience"?

To experience the same kind consciousness as a tardigrade - to know what it feels like to be a tardigrade. My argument is that, to us, feeling like a tardigrade would feel like nothing, like deep sleep, but such feelings would be significant to tardigrades.

(By the way, being animals, tardigrades don't belong to the unicellular protozoa but to the multicellular metazoa.)

Is there anything it feels like to be a tardigrade? Anyway, if there is, they surely don't know what it feels like to be a tardigrade in the sense of having introspective knowledge of it. If you have a feeling without being cognitively aware of it, in what sense is it significant to you? For instance, when I am in pain but don't know I am, it means nothing to me.

(Galen Strawson would object that in the case of experience, "the having is the knowing", with this kind of knowledge being non-propositional or objectual "knowledge by acquaintance" rather than introspective knowledge qua propositional "knowledge by description". That's the distinction between knowing something and knowing that something is the case/true. The question is whether you can know something/somebody without knowing anything about it/her/him—in the sense of having mental representations of it.)

I am saying that humans would be unable to perceive the simplest consciousnesses. They are too trivial as compared with our deeply complex psyches. We humans have long been dismissive of other organisms' capacity to feel and, while much improvement in this area his happened in the last century, it appears to me that we just lowered the bar, while remaining gatekeepers - of anthropocentric conceptions of what it feels like to be alive. It's hard not to be anthropocentric because it's all we have. There are still many researchers who believe that insects have no phenomenal consciousness - that being an insect does not feel like anything.
I am aware that you have a more nuanced view on this, and draw the line somewhere around brained nematodes. I am not convinced that we have solved as much of this puzzle as you are.

I am saying that natural consciousness is an exclusively zoological phenomenon, and there is certainly nothing anthropocentric about my saying so. I do not believe that all animals are phenomenally conscious, but I strongly tend to believe that all brained animals are, or at least those among them with non-primitive brains. (I know that "non-primitive" is an imprecise adjective.) It is uncertain whether insects are phenomenally conscious, but it isn't unlikely that they are—unless the higher-order theory of phenomenal consciousness is true, in which case the number of phenomenally conscious animal species is reduced drastically.

"Most generally, then, higher-order theories of phenomenal consciousness claim the following:
Higher Order Theory (In General): 
A phenomenally conscious mental state is a mental state (of a certain sort—see below) that either is, or is disposed to be, the object of a higher-order representation of a certain sort."

Source: https://plato.stanford.edu/entries/cons ... ss-higher/

Such higher-order representations require a highly developed cognitive apparatus enabling an inner awareness of one's conscious states, which most brained animals lack.

When I conduct the thought experiment I think of blind pulses within, like breaths or heartbeats, and tingling on the outside where the environment is sensed. There is no emotion, no care. Just sensations, attraction and repulsion, excitation and slowing. We call such things "biological machines" but that's just an analogy because they are obviously not machines - they are simple living, sensing beings.

One meaning of "machine" is "a combination of parts moving mechanically, as contrasted with a being having life, consciousness and will" (Oxford Dictionary of English). Given this meaning, living organisms aren't machines. But in the broadest sense a machine is a mechanism or dynamic system of any kind; so given this meaning, living organisms are machines too.

By the way, Carruthers argues that…

"…perception / belief / desire / planning / motor-control architectures are of very ancient ancestry indeed, being present even in insects and spiders. So the sort of cognitive architecture depicted in Figure 2.1 is likely to be shared by almost all animals that possess some sort of central nervous system."

(Carruthers, Peter. The Architecture of the Mind. Oxford: Oxford University Press, 2006. pp. 65-6)

[Atla]

I don't think so, because the anatomies of (C)NS-less organisms are well known; so if there were such functionally equivalent non-neuronal structures, the scientists would have found them already.

That is only an assumption, and not of the kind that tends to play out well in history.

No, since if "the anatomies of (C)NS-less organisms are well known"—which is true!—, there are no hidden, hitherto undiscovered organs or systems "that fulfil the same functions as brains."

Whatever kind of (conscious) mind they have, birds do have brains. Nonhuman animals needn't have a humanlike brain in order to have a (conscious) mind, but they must have some kind of brain or other. For example, octopus brains are very different from human brains, but they are brains all the same.

Nonetheless, the assumption was made that they lacked higher mental functions due to their lack of a cortex. They knew about the pallium, but not about some of its functions in bird brains.

Being wrong about the capacities of nonhuman minds doesn't mean being wrong about the necessity for brains.

By the same token, other equivalences may be found in other organisms. The octopus's non-centralised brains alert us to the fact that configurations of consciousness-shaping organs can be unexpectedly different.

An octopus does have a central(ized) nervous system!
Brains come in various sizes and shapes, but there are no brainlike nonbrains in organisms that are functionally and informationally equivalent to brains.

It is not the case that in the realm of speculation all hypotheses are equally (im)plausible or (im)probable. The hypothesis that nervous systems and especially central ones are necessary for conscious minds appears highly plausible and probable in the light of our scientific knowledge of nature, and there is no convincing evidence for its negation!

Yes, there's plenty of convincing circumstances for its negation - unexpected complexity and flexibility in the behaviours of non-brained organisms. It's not evidence, but it's real and often dismissed without investigation based on brain-based dogmas.

No, there isn't! There's just plenty of unjustified conclusions. For if complex and flexible forms of behavior are brain-independent, it by no means follows that phenomenal consciousness is brain-independent too.

"Most researchers accept that even quite complex perception, cognition, and control of action can go on entirely 'in the dark'."

(Godfrey-Smith, Peter. "The Evolution of Consciousness in Phylogenetic Context." In The Routledge Handbook of Philosophy of Animal Minds, edited by Kristin Andrews and Jacob Beck, 216-226. London: Routledge, 2018. p. 220)

It would be very basic, but it may well feel like something to be a microbe - or certain microbes (who knows?).

"May" in the sense of "logically possible", yes; but given what we know about the morphology and physiology of bacteria and protozoa (unicellular microorganisms), it is extremely improbable.

There are levels of (intransitive and transitive) consciousness in the sense of levels of awakeness or alertness, or of awareness (perception, cognition) of oneself or one's environment, and there are levels of intelligence; but what is a "level of sentience"?

To experience the same kind consciousness as a tardigrade - to know what it feels like to be a tardigrade. My argument is that, to us, feeling like a tardigrade would feel like nothing, like deep sleep, but such feelings would be significant to tardigrades.

(By the way, being animals, tardigrades don't belong to the unicellular protozoa but to the multicellular metazoa.)

Is there anything it feels like to be a tardigrade? Anyway, if there is, they surely don't know what it feels like to be a tardigrade in the sense of having introspective knowledge of it. If you have a feeling without being cognitively aware of it, in what sense is it significant to you? For instance, when I am in pain but don't know I am, it means nothing to me.

(Galen Strawson would object that in the case of experience, "the having is the knowing", with this kind of knowledge being non-propositional or objectual "knowledge by acquaintance" rather than introspective knowledge qua propositional "knowledge by description". That's the distinction between knowing something and knowing that something is the case/true. The question is whether you can know something/somebody without knowing anything about it/her/him—in the sense of having mental representations of it.)

I am saying that humans would be unable to perceive the simplest consciousnesses. They are too trivial as compared with our deeply complex psyches. We humans have long been dismissive of other organisms' capacity to feel and, while much improvement in this area his happened in the last century, it appears to me that we just lowered the bar, while remaining gatekeepers - of anthropocentric conceptions of what it feels like to be alive. It's hard not to be anthropocentric because it's all we have. There are still many researchers who believe that insects have no phenomenal consciousness - that being an insect does not feel like anything.
I am aware that you have a more nuanced view on this, and draw the line somewhere around brained nematodes. I am not convinced that we have solved as much of this puzzle as you are.

I am saying that natural consciousness is an exclusively zoological phenomenon, and there is certainly nothing anthropocentric about my saying so. I do not believe that all animals are phenomenally conscious, but I strongly tend to believe that all brained animals are, or at least those among them with non-primitive brains. (I know that "non-primitive" is an imprecise adjective.) It is uncertain whether insects are phenomenally conscious, but it isn't unlikely that they are—unless the higher-order theory of phenomenal consciousness is true, in which case the number of phenomenally conscious animal species is reduced drastically.

"Most generally, then, higher-order theories of phenomenal consciousness claim the following:
Higher Order Theory (In General): 
A phenomenally conscious mental state is a mental state (of a certain sort—see below) that either is, or is disposed to be, the object of a higher-order representation of a certain sort."

Source: https://plato.stanford.edu/entries/cons ... ss-higher/

Such higher-order representations require a highly developed cognitive apparatus enabling an inner awareness of one's conscious states, which most brained animals lack.

When I conduct the thought experiment I think of blind pulses within, like breaths or heartbeats, and tingling on the outside where the environment is sensed. There is no emotion, no care. Just sensations, attraction and repulsion, excitation and slowing. We call such things "biological machines" but that's just an analogy because they are obviously not machines - they are simple living, sensing beings.

One meaning of "machine" is "a combination of parts moving mechanically, as contrasted with a being having life, consciousness and will" (Oxford Dictionary of English). Given this meaning, living organisms aren't machines. But in the broadest sense a machine is a mechanism or dynamic system of any kind; so given this meaning, living organisms are machines too.

By the way, Carruthers argues that…

"…perception / belief / desire / planning / motor-control architectures are of very ancient ancestry indeed, being present even in insects and spiders. So the sort of cognitive architecture depicted in Figure 2.1 is likely to be shared by almost all animals that possess some sort of central nervous system."

(Carruthers, Peter. The Architecture of the Mind. Oxford: Oxford University Press, 2006. pp. 65-6)

How many of these 'something out of nothing': 'phenomenal consciousness out of phenomenal unconsciousness' impossible philosophical theories are there?

[Atla]

How many of these 'something out of nothing': 'phenomenal consciousness out of phenomenal unconsciousness' impossible philosophical theories are there?

It's a bit like searching for gods, we couldn't find the first 10000 gods we were searching for, but we hope all the same that the 10001st one will show up somehow. Hope dies last.