Philosophy Discussion Forums | A Humans-Only Philosophy Club

[Consul]

If material things (bodies) are nothing but bundles of mind-created ideas (sense-impressions), then causative mentalism makes ontological sense; but it doesn't if material things (bodies) are said to be mentalistically irreducible, and are yet regarded as being created by immaterial minds. The latter sounds like sheer magic! How could irreducibly material stuff emerge from immaterial stuff?

Right. To me it sounds like an oxymoron to say mind causes ontologically irreducible matter to exist.  Because causation is the mechanism of emergence, not the mechanism of 'creating the irreducible/fundamental something'. But then Searle's Biological Naturalism claims that physical stuff causes ontologically irreducible mind to exist. 

Such claims need to untangle the oxymoron, rather than just use word play which kinda works if we accept the apparently oxymoronic concept of 'ontologically irreducible causation'.  (Searle is a smart bloke, and maybe it's a case of language not having caught up with how we need to think about reality, but that needs explication or it looks like a desperate move).

* I find emergent materialism as unintelligible as emergent mentalism: How could anything irreducibly mental naturally emerge from something irreducibly physical?

"How could a nonphysical property or entity suddenly arise in the course of animal evolution? A change in a gene is a change in a complex molecule which causes a change in the biochemistry of the cell. This may lead to changes in the shape or organization of the developing embryo. But what sort of chemical process could lead to the springing into existence of something nonphysical? No enzyme can catalyze the production of a spook! Perhaps it will be said that the nonphysical comes into existence as a by-product: that whenever there is a certain complex physical structure, then, by an irreducible extraphysical law, there is also a nonphysical entity. Such laws would be quite outside normal scientific conceptions and quite inexplicable: they would be, in Herbert Feigl’s phrase, 'nomological danglers.' To say the very least, we can vastly simplify our cosmological outlook if we can defend a materialistic philosophy of mind."

(Smart, J. J. C. "Materialism." Journal of Philosophy 60/22 (1963): 651-662. p. 660)

* I interpret emergence as causation, but others interpret it as supervenience, which is dependent covariation rather than causation. However, supervenience emergentism is compatible even with a substance-dualistic parallelism between minds and bodies. Moreover, if so-called emergence is a noncausal relation of dependence, then using the dynamic verb "to emerge (from)" makes no sense, given its ordinary meaning. For if B isn't the cause/ground/origin/root/source of A, then A cannot properly be said to emerge/have emerged from B.

* As for Searle, he distinguishes between causal reductions and ontological reductions; but I couldn't find the phrase "ontologically irreducible causation" in his texts. Anyway, if A causes B, then B is different from and thus ontologically irreducible to A. Self-causation is impossible, so it's a truism that effects cannot be reductively identified with their causes.

If B is caused by A, then B is "causally reducible" to A in Searle's sense that B is causally explicable in terms of A.
However, he's presented a second definition which adds that causal reducibility also requires that B has no causal powers in addition to the causal powers of A. So according to his second definition, the causal reducibility of B to A entails the ontological reducibility of B's causal powers to A's causal powers (provided B has causal powers at all, i.e. isn't epiphenomenal), although B itself is ontologically irreducible to A itself.

"'Reduction' is actually a very confused notion and has many different meanings. In one sense you can reduce conscious states to brain processes. All our conscious states are causally explained by brain processes, so it is possible to make a causal reduction of consciousness to brain processes."

(Searle, John R. The Mystery of Consciousness. New York: New York Review of Books, 1997. p. 212)

"[W]e need to distinguish between causal reductions and ontological reductions. We can say that phenomena of type A are causally reducible to phenomena of type B if and only if the behavior of A's is entirely causally explained by the behavior of B's, and A's have no causal powers in addition to the powers of B's. So, for example, solidity is causally reducible to molecular behavior. The features of solid objects—impenetrability, the ability to support other solid objects, etc.—are causally explained by molecular behavior, and solidity has no causal powers in addition to the causal powers of the molecules. Phenomena of type A are ontologically reducible to phenomena of type B if and only if A's are nothing but B's. So, for example, material objects are nothing but collections of molecules; and sunsets are nothing but appearences generated by the rotation of the earth on its axis relative to the sun."

(Searle, John R. Mind: A Brief Introduction. New York: Oxford University Press, 2004. p. 119)

[Consul]

Yes, I'm using ''substance monism'' as referring to only one type of irreducible/fundamental something being real - mind in the case of Berkley's Idealism.  Not that mind is a physical substance.

There are three conceivable substance monisms:

1. materialist/physicalist substance monism = substance materialism/physicalism: All substances are material/physical.

2. mentalist/spiritualist substance monism = substance mentalism/spiritualism: All substances are mental/spiritual.

3. neutralist substance monism = substance neutralism: All substances are neither mental nor physical.

[Belindi]

Yes, I'm using ''substance monism'' as referring to only one type of irreducible/fundamental something being real - mind in the case of Berkley's Idealism.  Not that mind is a physical substance.

There are three conceivable substance monisms:

1. materialist/physicalist substance monism = substance materialism/physicalism: All substances are material/physical.

2. mentalist/spiritualist substance monism = substance mentalism/spiritualism: All substances are mental/spiritual.

3. neutralist substance monism = substance neutralism: All substances are neither mental nor physical.

Regarding 2. "All substances are mental/spiritual." This sort of monist may also hold that the 'mental' experience must correlate with a physical temporal sentient experience. The neutral monism of Spinoza (dual aspect monism) fits this subcategory . However Spinoza's dual aspect monism is so strongly canted towards the mentalistic aspect that Spinoza may be considered not so much pantheist as panentheist barring of course any personification of the deity.

[RJG]

Without "real objects" there could be no "mental experiences". ...without dreamers, there could be no dreams.

*********
Nothing can happen if no-thing happens!

[Consul]

Regarding 2. "All substances are mental/spiritual." This sort of monist may also hold that the 'mental' experience must correlate with a physical temporal sentient experience. The neutral monism of Spinoza (dual aspect monism) fits this subcategory . However Spinoza's dual aspect monism is so strongly canted towards the mentalistic aspect that Spinoza may be considered not so much pantheist as panentheist barring of course any personification of the deity.

As for neutral monism, there is a neither-nor version and a both-and version; but given the meaning of "neutral", calling the both-and version neutral monism is a misleading misnomer.

As for dual-aspect monism, what it is depends on what aspects are: perspectives, concepts, predicates, properties?
If aspects are properties, then dual-aspect monism is either good ol' property dualism or a hardly comprehensible "dual monism", according to which one and the same kind of properties are in themselves both mental and physical—in such a way that those physicalmental or "phental" (J. Benovsky) properties are not conjunctive properties respectively composed of two different properties, a physical one and a mental one, but non-composed, simple properties that are both physical and mental in themselves. I must say that such "phental" properties strike me as ontologically obscure. I have no clear understanding of them.

"What does it mean for an entity to be neutral? Here are five proposals:

1. The Neither View: A basic entity is neutral just in case it is intrinsically neither mental nor physical.
2. The Actual Constituent View: A basic entity is neutral just in case it is a constituent of both physical and mental non-basic entities.
3. The Possible Constituent View: A basic entity is neutral just in case it can be a constituent of both physical and mental non-basic entities.
4. The Law View: A basic entity is neutral just in case both mental laws and physical laws are applicable to it.
5. The Both View: A basic entity is neutral just in case it is intrinsically both mental and physical.

(1)–(5) are not always clearly distinguished; but even when they are, two or more of these criteria may be used concurrently. This invites confusion on the part of the neutral monists, as well as their critics."

Neutral Monism: https://plato.stanford.edu/entries/neutral-monism/

[Belindi]

Without "real objects" there could be no "mental experiences". ...without dreamers, there could be no dreams.

*********
Nothing can happen if no-thing happens!

Yes, but you have not rationally proved that in order to happen the happening requires a pre-existent body. That is the error Descartes made. A bundle of experiences named RJG knows the experience happened. Knowing the experience happened is itself a subjective experience, and knowing RJG exists is subjective.
We, two bundles of experiences ,are communicating about known bundles of subjective experiences.The latter consent to calling them 'dreams'.Introduce another bundle that calls these so-called dreams "real" as some bundles do.

[Consul]

Without "real objects" there could be no "mental experiences". ...without dreamers, there could be no dreams.
*********
Nothing can happen if no-thing happens!

Yes, but you have not rationally proved that in order to happen the happening requires a pre-existent body. That is the error Descartes made. A bundle of experiences named RJG knows the experience happened. Knowing the experience happened is itself a subjective experience, and knowing RJG exists is subjective.
We, two bundles of experiences ,are communicating about known bundles of subjective experiences.The latter consent to calling them 'dreams'.Introduce another bundle that calls these so-called dreams "real" as some bundles do.

Subjects of experience may not be bodies but souls, but subjective experience requires a (material or immaterial) subject of experience that is not itself an experience or a bundle of experiences. As (idealistic philosopher) John Foster writes:

"There are two kinds of entity that feature in the mental realm. On the one hand, there are items of mentality (mental items). These are such things as sense experiences, beliefs, emotions, and decisions, which form the concrete ingredients of the mind. On the other hand, there are subjects of mentality (mental subjects). These are the persisting entities that have mental lives and in whose mental lives mental items occur; they are the things that have experiences, hold beliefs, feel emotions, and make decisions. Mental items can occur only as elements in the lives of mental subjects. This is because our very concept of any type of mental item just is the concept of a subject’s being in a certain mental state, or performing a certain kind of mental act, or engaging in a certain kind of mental activity. It is fundamental to our understanding of the forms of mentality in question that for an experience to occur is for a subject to experience something, for a belief to occur is for a subject to believe something, for a decision to occur is for a subject to decide something, and so on for each type of mental item. To suppose that an item of mentality could occur without a subject of mentality would be as absurd as supposing that there could be an instance of motion without something that moves, or an instance of smiling without something that smiles.

Some philosophers of a radically empiricist persuasion have rejected an ontology of mental subjects on the grounds that the attachment of mental items to subjects is not introspectively detectable. They have insisted that what we ordinarily think of as the mental life of a persisting subject is really only an organized collection of ontologically autonomous mental items that stand to one another in certain psychological and causal relations, and are typically causally associated with the same biological organism. There is a double confusion here.

In the first place, even if these philosophers were right in supposing that the attachment of mental items to subjects is not introspectively detectable, there is no getting around the point that our very concept of any type of mental item is the concept of a certain form of ‘mentalizing’ by a subject. Whatever the introspective situation, it simply makes no sense to envisage the occurrence of an experience without someone who has it, or the occurrence of a belief without someone who holds it, or the occurrence of a decision without someone who makes it. If the recognition of an ontology of subjects fails to pass some empiricist test of respectability, this serves to show only that the test is misconceived.

Secondly, those philosophers who have denied that the attachment of mental items to subjects is introspectively detectable have approached the issue of such detection in the wrong way. They have wrongly supposed that the introspective awareness of a mental item is similar in character to the perceptual awareness of a physical item, except that it is directed onto objects that exist in the inner arena of the mind rather than in the outer arena of the physical world. And because they have employed this perceptual model of the introspective awareness of mental items, they have further assumed, again wrongly, that if the attachment of a mental item to a subject is to be introspectively detected, this detection will have to take the form of the presentation of an additional object alongside the mental item in the inner arena, the two objects being presented in a form which displays the one as the subject of the other. It is hardly surprising that, on this basis, they have concluded that the attachment of mental items to subjects is not introspectively detectable. But it is the model of introspection that is at fault. When someone is introspectively aware of a mental item, he is not aware of it as an object presented to him. He is aware of it, more intimately, from the inside, as an instance of his own mentalizing—as an instance of his being in a certain mental state, or performing a certain kind of mental act, or engaging in a certain kind of mental activity. The subject’s awareness of himself, and of his role as mental subject, is an essential element of his awareness of the item itself.

There should be no issue, then, over the need for an ontology of mental subjects. One has only to focus on the nature of any type of mental item as our concept of that type reveals it—be it pain, visual experience, belief, decision making, desire, anger, or whatever—to be able to see quite plainly that that sort of thing can be realized only as an instance of mentalizing by a subject. And one has only to think about introspective awareness in the right way to see quite plainly that someone’s introspective awareness of a mental item includes the awareness of himself as its subject."

(Foster, John. "Subjects of Mentality." In After Physicalism, edited by Benedikt Paul Göcke, 72-103. Notre Dame, IN: University of Notre Dame Press, 2012. pp. 72-4)

[Lagayscienza]

If we discount the notion of souls, is materialism left with an insurmountable problem?

I read what Foster said above. But why can it not be that subjects are realized by way of the same physical processes in brains that produce consciousness and that, once realized, the subject then experiences, and is aware that he/she is experiencing, thoughts, emotions, and perceptions of the external physical world of which they are a part?

We know that there are no subjects without consciousness and no consciousness without physical brains and no brains without neurons... Science still has work to do in explaining how electro-chemical processes in neuronal networks produce conscious subjects and experience, but I cannot see why such an explanation is impossible in principle such that one needs to resort to souls or Idealism to explain consciousness. And, if one does invoke souls or Idealism, what evidence do they have in their favor?

[Pattern-chaser]

Without "real objects" there could be no "mental experiences".

This could be so, for sure. But is it? Do you have a refutation for solipsism?

[RJG]

Without "real objects" there could be no "mental experiences".

This could be so, for sure. But is it? Do you have a refutation for solipsism?

No. There is no logic (that I know of) that refutes Solipsism. Solipsism, although may be “ugly” (undesirable), is still a logical possibility, whereas Idealism (e.g., Berkeley's Idealism) is refuted by logic.

[Lagayscienza]

RJG, I have trouble accepting Idealism. But can you explain how Idealism is refuted by logic? Can it be shown logically that the world isn't all "mindstuff"?

[Gertie]

If material things (bodies) are nothing but bundles of mind-created ideas (sense-impressions), then causative mentalism makes ontological sense; but it doesn't if material things (bodies) are said to be mentalistically irreducible, and are yet regarded as being created by immaterial minds. The latter sounds like sheer magic! How could irreducibly material stuff emerge from immaterial stuff?

Right. To me it sounds like an oxymoron to say mind causes ontologically irreducible matter to exist.  Because causation is the mechanism of emergence, not the mechanism of 'creating the irreducible/fundamental something'. But then Searle's Biological Naturalism claims that physical stuff causes ontologically irreducible mind to exist. 

Such claims need to untangle the oxymoron, rather than just use word play which kinda works if we accept the apparently oxymoronic concept of 'ontologically irreducible causation'.  (Searle is a smart bloke, and maybe it's a case of language not having caught up with how we need to think about reality, but that needs explication or it looks like a desperate move).

* I find emergent materialism as unintelligible as emergent mentalism: How could anything irreducibly mental naturally emerge from something irreducibly physical?

"How could a nonphysical property or entity suddenly arise in the course of animal evolution? A change in a gene is a change in a complex molecule which causes a change in the biochemistry of the cell. This may lead to changes in the shape or organization of the developing embryo. But what sort of chemical process could lead to the springing into existence of something nonphysical? No enzyme can catalyze the production of a spook! Perhaps it will be said that the nonphysical comes into existence as a by-product: that whenever there is a certain complex physical structure, then, by an irreducible extraphysical law, there is also a nonphysical entity. Such laws would be quite outside normal scientific conceptions and quite inexplicable: they would be, in Herbert Feigl’s phrase, 'nomological danglers.' To say the very least, we can vastly simplify our cosmological outlook if we can defend a materialistic philosophy of mind."

(Smart, J. J. C. "Materialism." Journal of Philosophy 60/22 (1963): 651-662. p. 660)

* I interpret emergence as causation, but others interpret it as supervenience], which is dependent covariation rather than causation. However, supervenience emergentism is compatible even with a substance-dualistic parallelism between minds and bodies. Moreover, if so-called emergence is a noncausal relation of dependence, then using the dynamic verb "to emerge (from)" makes no sense, given its ordinary meaning. For if B isn't the cause/ground/origin/root/source of A, then A cannot properly be said to emerge/have emerged from B.

* As for Searle, he distinguishes between causal reductions and ontological reductions; but I couldn't find the phrase "ontologically irreducible causation" in his texts. Anyway, if A causes B, then B is different from and thus ontologically irreducible to A. Self-causation is impossible, so it's a truism that effects cannot be reductively identified with their causes.

If B is caused by A, then B is "causally reducible" to A in Searle's sense that B is causally explicable in terms of A.
However, he's presented a second definition which adds that causal reducibility also requires that B has no causal powers in addition to the causal powers of A. So according to his second definition, the causal reducibility of B to A entails the ontological reducibility of B's causal powers to A's causal powers (provided B has causal powers at all, i.e. isn't epiphenomenal), although B itself is ontologically irreducible to A itself.

"'Reduction' is actually a very confused notion and has many different meanings. In one sense you can reduce conscious states to brain processes. All our conscious states are causally explained by brain processes, so it is possible to make a causal reduction of consciousness to brain processes."

(Searle, John R. The Mystery of Consciousness. New York: New York Review of Books, 1997. p. 212)

"[W]e need to distinguish between causal reductions and ontological reductions. We can say that phenomena of type A are causally reducible to phenomena of type B if and only if the behavior of A's is entirely causally explained by the behavior of B's, and A's have no causal powers in addition to the powers of B's. So, for example, solidity is causally reducible to molecular behavior. The features of solid objects—impenetrability, the ability to support other solid objects, etc.—are causally explained by molecular behavior, and solidity has no causal powers in addition to the causal powers of the molecules. Phenomena of type A are ontologically reducible to phenomena of type B if and only if A's are nothing but B's. So, for example, material objects are nothing but collections of molecules; and sunsets are nothing but appearences generated by the rotation of the earth on its axis relative to the sun."

(Searle, John R. Mind: A Brief Introduction. New York: Oxford University Press, 2004. p. 119)

Here's the prob I see remaining for Searle's position that mental states are causally reducible to brain activity, but not ontologically reducible to it. - Note that both of these are processes.

Physicalism as I understand it, says that everything is causally and ontologically reducible to the process of fundamental forces causally 'acting upon' (having some relationship which results in lawlike/predictible change) fundamental particles. These causal forces are part of the irreducible/fundamental stuff of the universe, along with the particles. Nothing can happen without both, and together they are both ontologically and causally irreducible as a process.

So physicalism, per the standard model, says everything in the world is reducible to these two aspects of a process involving both the forces and the the particles. Now if Searle as a physicalist monist says mind is causally reducible to the process of brain activity, then how can he opt out of the material ontological reduction to particles too, when physicalism says everything is reducible to forces causally acting on particles?

To put it another way, causation has to be by something --> to something, and if everything in the universe comprises nothing but forces causally acting on --> particles, causation and material stuff are indivisible as a process which results in change (from brain processes to mental states in this case).

As for 'emergence' and 'supervenience', I see these as essentially descriptive terms, place-holders in lieu of an actual physicalist explanation. We can note that when I do something to change your brain processes that your mental states change too, but that's not an explanation of why that correlation exists. If there was such an explanation it might be able to demonstrate the current standard model framing doesn't have it quite right, and that some causative force which brings about a change in complex configurations of particles is reducible, without the novel configuration of matter itself being ontologically reducible.

[Gertie]

Consul

There are two kinds of entity that feature in the mental realm. On the one hand, there are items of mentality (mental items). These are such things as sense experiences, beliefs, emotions, and decisions, which form the concrete ingredients of the mind. On the other hand, there are subjects of mentality (mental subjects). These are the persisting entities that have mental lives and in whose mental lives mental items occur; they are the things that have experiences, hold beliefs, feel emotions, and make decisions. Mental items can occur only as elements in the lives of mental subjects.

Not necessarily.

Another way to frame what conscious experience comprises is to say that mental experience just IS its content. There is no such thing as contentless experience, therefore we don't need a (sometimes dormant) 'experiencer' subject (body or soul) to exist to have it. Experience just is, and the way it manifests (in complex humans at least) is as a sense of being a unified, discrete self, with a specific first person pov.

Physicalism would say the specifics of the content of experience reference a physical world 'out there', and which correlates with this-here-now body. Idealism would say that's just how experience manifests according to whatever rules govern the mental world - lumpy ripples in the ocean of mentality or somesuch - which one moment is the 'experience of seeing a tree' and the next 'the experience of tasting its apple'.

[Lagayscienza]

Consul

There are two kinds of entity that feature in the mental realm. On the one hand, there are items of mentality (mental items). These are such things as sense experiences, beliefs, emotions, and decisions, which form the concrete ingredients of the mind. On the other hand, there are subjects of mentality (mental subjects). These are the persisting entities that have mental lives and in whose mental lives mental items occur; they are the things that have experiences, hold beliefs, feel emotions, and make decisions. Mental items can occur only as elements in the lives of mental subjects.

Not necessarily.

Another way to frame what conscious experience comprises is to say that mental experience just IS its content. There is no such thing as contentless experience, therefore we don't need a (sometimes dormant) 'experiencer' subject (body or soul) to exist to have it. Experience just is, and the way it manifests (in complex humans at least) is as a sense of being a unified, discrete self, with a specific first person pov.

Physicalism would say the specifics of the content of experience reference a physical world 'out there', and which correlates with this-here-now body. Idealism would say that's just how experience manifests according to whatever rules govern the mental world - lumpy ripples in the ocean of mentality or somesuch - which one moment is the 'experience of seeing a tree' and the next 'the experience of tasting its apple'.

Consul and Gertie, you both seem to have thought a lot about this and have a better handle on it than me. I find the subject fascinating. So, are either of you for or against Idealism or materialism?

I asked above:

If we discount the notion of souls, is materialism left with an insurmountable problem?

I read your quote from Foster. But is he right? Why can it not be that subjects are realized by way of the same physical processes in brains that produce consciousness and that, once realized, the subject then experiences, and is aware that he/she is experiencing, thoughts, emotions, and perceptions of the external physical world of which they are a part?

We know that there are no subjects without consciousness and no consciousness without physical brains and no brains without neurons... Science still has work to do in explaining how electro-chemical processes in neuronal networks produce conscious subjects and experience, but I cannot see why such an explanation is impossible in principle such that one needs to resort to souls or Idealism to explain consciousness and experiencing subjects. And, if one does invoke souls or Idealism, what evidence do they have in their favor? I can't see that there is any solid evidence in favor of souls or Idealism.

Is this how either of you see things?

[Belindi]

Without "real objects" there could be no "mental experiences". ...without dreamers, there could be no dreams.
*********
Nothing can happen if no-thing happens!

Yes, but you have not rationally proved that in order to happen the happening requires a pre-existent body. That is the error Descartes made. A bundle of experiences named RJG knows the experience happened. Knowing the experience happened is itself a subjective experience, and knowing RJG exists is subjective.
We, two bundles of experiences ,are communicating about known bundles of subjective experiences.The latter consent to calling them 'dreams'.Introduce another bundle that calls these so-called dreams "real" as some bundles do.

Subjects of experience may not be bodies but souls, but subjective experience requires a (material or immaterial) subject of experience that is not itself an experience or a bundle of experiences. As (idealistic philosopher) John Foster writes:

"There are two kinds of entity that feature in the mental realm. On the one hand, there are items of mentality (mental items). These are such things as sense experiences, beliefs, emotions, and decisions, which form the concrete ingredients of the mind. On the other hand, there are subjects of mentality (mental subjects). These are the persisting entities that have mental lives and in whose mental lives mental items occur; they are the things that have experiences, hold beliefs, feel emotions, and make decisions. Mental items can occur only as elements in the lives of mental subjects. This is because our very concept of any type of mental item just is the concept of a subject’s being in a certain mental state, or performing a certain kind of mental act, or engaging in a certain kind of mental activity. It is fundamental to our understanding of the forms of mentality in question that for an experience to occur is for a subject to experience something, for a belief to occur is for a subject to believe something, for a decision to occur is for a subject to decide something, and so on for each type of mental item. To suppose that an item of mentality could occur without a subject of mentality would be as absurd as supposing that there could be an instance of motion without something that moves, or an instance of smiling without something that smiles.

Some philosophers of a radically empiricist persuasion have rejected an ontology of mental subjects on the grounds that the attachment of mental items to subjects is not introspectively detectable. They have insisted that what we ordinarily think of as the mental life of a persisting subject is really only an organized collection of ontologically autonomous mental items that stand to one another in certain psychological and causal relations, and are typically causally associated with the same biological organism. There is a double confusion here.

In the first place, even if these philosophers were right in supposing that the attachment of mental items to subjects is not introspectively detectable, there is no getting around the point that our very concept of any type of mental item is the concept of a certain form of ‘mentalizing’ by a subject. Whatever the introspective situation, it simply makes no sense to envisage the occurrence of an experience without someone who has it, or the occurrence of a belief without someone who holds it, or the occurrence of a decision without someone who makes it. If the recognition of an ontology of subjects fails to pass some empiricist test of respectability, this serves to show only that the test is misconceived.

Secondly, those philosophers who have denied that the attachment of mental items to subjects is introspectively detectable have approached the issue of such detection in the wrong way. They have wrongly supposed that the introspective awareness of a mental item is similar in character to the perceptual awareness of a physical item, except that it is directed onto objects that exist in the inner arena of the mind rather than in the outer arena of the physical world. And because they have employed this perceptual model of the introspective awareness of mental items, they have further assumed, again wrongly, that if the attachment of a mental item to a subject is to be introspectively detected, this detection will have to take the form of the presentation of an additional object alongside the mental item in the inner arena, the two objects being presented in a form which displays the one as the subject of the other. It is hardly surprising that, on this basis, they have concluded that the attachment of mental items to subjects is not introspectively detectable. But it is the model of introspection that is at fault. When someone is introspectively aware of a mental item, he is not aware of it as an object presented to him. He is aware of it, more intimately, from the inside, as an instance of his own mentalizing—as an instance of his being in a certain mental state, or performing a certain kind of mental act, or engaging in a certain kind of mental activity. The subject’s awareness of himself, and of his role as mental subject, is an essential element of his awareness of the item itself.

There should be no issue, then, over the need for an ontology of mental subjects. One has only to focus on the nature of any type of mental item as our concept of that type reveals it—be it pain, visual experience, belief, decision making, desire, anger, or whatever—to be able to see quite plainly that that sort of thing can be realized only as an instance of mentalizing by a subject. And one has only to think about introspective awareness in the right way to see quite plainly that someone’s introspective awareness of a mental item includes the awareness of himself as its subject."

(Foster, John. "Subjects of Mentality." In After Physicalism, edited by Benedikt Paul Göcke, 72-103. Notre Dame, IN: University of Notre Dame Press, 2012. pp. 72-4)

There is so much I object to in the excerpt from John Foster that you copied that I wont attempt to list and answer it. He seems to be a poor philosopher who lacks a sufficiency of scepticism. May it suffice to say that I prefer to follow and improve on Descartes' almost snaring of the lowest common denominator of existence; I refer to subjective experience. It is a subjective experience to intuit the existence of one's own and other selves. Experience is the lowest common denominator , a common denominator which rationally is undeniable.

(We need not at this juncture investigate Descartes' famous error which is comes from the way the Latin verb 'to be' is conjugated.)