Continuity:
An Ontological Proposal for the Mind-Body Problem
Abstract
This
paper addresses the mind-body problem by highlighting the concept of continuity.
Building on philosophical definitions, it introduces an "ontology of
continuity" thesis to bridge the mental and the physical. Based on the
thesis, the paper introduces a “neuro-subjective interactive (NSI)” model,
which incorporates empirical studies from brain science. The model suggests
that subjective experiences and neural activities are inter-dependent. Instead
of separating between human mentality and its physical base, the paper posits that
our mentality is constituted by both physical (neural) and non-physical
(subjective) elements. This approach addresses two major challenges in the
mind-body problem: causal overdetermination and physical causal closure.
Keywords:
supervenience; continuity; panpsychism; overdetermination; physicalism
1.
Introduction
This
paper delves into the ontological nature of the mental and physical. But what
is ontology? Broadly, it is understood as the study of being. According to
Hofweber (2023), there are “at least two parts to the overall philosophical
project of ontology” (Section 3.1). The first one concerns “what there is, what
exists, what the stuff of reality is made out of.” The second one involves
“what the most general features and relations of these things are.” However,
clarifying these two aspects is not an easy task. Hofweber also points out that
“[o]ne of the troubles with ontology is that it not only isn’t clear what there
is, it also isn’t so clear how to settle questions about what there is.” So, should
we abandon this inquiry? Certainly not.
Hofweber
argues that the “larger discipline of ontology” involves the “study of
ontological commitment, i.e. what we or others are committed to.” Given that
the mind-body problem is one of the most intensely debated topics today, it is
worth investigating the relationships between the mental and physical by
assuming their ontological validity. That is, we need not be led to believe,
unlike the ancient Greek philosopher Zeno, that the world is an illusion.
When
examining the mind-body problem, we face the fundamental question: what is the
nature of the mental, and how does it relate to the physical? In seeking to
answer this question, this paper emphasizes the significance of continuity in
both mental and physical realms. Specifically, the paper proposes that
continuity be viewed as an ontological construct that bridges the two.
To
that end, Section 2 introduces key definitions regarding the mind-body problem.
Subsequently, Section 3 provides an “ontology of continuity” thesis by
comparing physicalism and idealism. Section 4 investigates several features of
our mind by referring to several empirical studies. Finally, Section 5 presents
a supervenience model that attempts to resolve Jaegwon Kim’s causal
overdetermination and causal closure of the physical. Section 6 discusses
potential critiques of this paper and also considers other positions in the
mind-body problem debate. The conclusion will summarize the paper’s major points
and suggest that it offers a meaningful extension to the debate surrounding the
mind-body problem.
2.
Definitions
Physicalists
argue that the mental is ultimately physical. Although “the world might contain
many items that at first glance don’t seem physical – items of a biological, or
psychological, or moral, or social or mathematical nature,” “at the end of the
day such items are physical, or at least bear an important relation to the
physical” (Stoljar, 2022, Section 0). The word “physical” sounds intuitive. It
can refer to anything that can be perceived through our senses. But how exactly
should we define it? According to Ney (2008), “many interpret physicalism as
the doctrine that everything is physical, where to be physical is to be
countenanced by physics” (p. 1035). However, Hempel (1980) notes that “the
physicalistic claim that the language of physics can serve as a unitary
language of science is inherently obscure” (p. 194). Why? Physics is constantly
evolving, as “it will no doubt undergo further changes” (p. 195). This means
that physics is yet incomplete, which suggests that definition of physicalism
rests upon an unstable foundation. Considering the difficulty in formulating
precise definitions in the mind-body problem, this paper will use conditional
statements for definitions. For instance, instead of stating that “The physical
is X,” this paper will use the form: “If something is physical, it is X.” See
below:
Definitions
(1) If something is physical, it has a
spatiotemporal form but has no awareness.
(2) If something is
spatiotemporal, it is spatially/temporally continuous.
(3) If something is
continuous, it forms its own type of wholeness through connectivity.
(4) If something is
spatial, it involves a simultaneous representation of connectivity.
(5) If something is
temporal, it involves a successive representation of connectivity.
(6) If something is
mental, it has awareness and perceives the spatiotemporal form of the physical.
(7) If something has
awareness, it continuously retains
its self-identity temporally.
(8) If something
focuses on an object, it encounters the otherness of the object.
(9) If something is
perceived, the perception begins as awareness occurs to focus on the something
as its spatiotemporal form is immediately externalized (i.e., “otherness” is
manifested).
Panpsychists
may have a different idea about (1). They hold “that everything is conscious,
which many find counterintuitive” (Chalmers, 1996, p. 153). Nonetheless,
Chalmers claims that “we ought to take the possibility of some sort of
panpsychism seriously,” since “there seem to be no knockdown arguments against
the view” (p. 299). However, for the sake of discussion, this paper does not
accept that all physical matter has a certain form of consciousness on an
individual level. Instead, this paper proposes that the universe as a whole may possess a mental element.
Regarding
(2), we say that something spatiotemporal is necessarily continuous, for
otherwise it can have no significance in the empirical world. If something is
spatial, it necessarily occupies space. Everything that occupies space has an
extension. Or even a segment within empty space is an extension within it. An
extension exhibits internal connectivity. Similarly, if something is temporal,
it necessarily has an extension in temporal passage. Anything lacking extension
in temporal passage is atemporal.
(3)
must be understood with caution. The “continuous” as defined therein differs
from the notion of mathematical continuity. It is also unrelated to whether our
space or time is seamlessly continuous or gappy. The core feature of continuity
is that seemingly isolated features can combine to create a unified whole. For
instance, a melody is spatiotemporally continuous as its acoustic wave
propagates physically through the air. The crests and troughs of the wave,
though they are seen as opposites, constitute one melodious sound. Similarly,
two particles of a tangible object, despite their spatial separation, are still
the components of the same object. The object’s continuity is demonstrated
through the numerous connectivities of such particles that constitute the
object. These connectivities are static rather than dynamic. Thus, (4) states
that the “spatial” involves a simultaneous representation of connectivity.
Meanwhile,
(5) states that the “temporal” involves a successive representation of
connectivity. It has a dynamic element. Or it can be thought of as a flow. For
example, the motion of an object in our eyes can be interpreted to be a
collection of successive snapshots of the same object. Although these snapshots
are separated by intervals, they create an impression of oneness in the
temporal dimension.
According
to (6), mentality has two features: awareness and perception. (7) defines
awareness based on the retention of self-identity. But what is “retention”? This
is well established in Husserl (1928/1991, pp. 25-29). For instance, by taking
the “tone” (sound) as an instance of a “hylectic datum” (i.e., sensory datum),
Husserl states: “It begins and ends; and after it has ended, its whole
duration-unity, the unity of the whole process in which it begins and ends,
‘recedes’ into the ever more distant past. In this sinking back, I still ‘hold
onto it,’ have it in a ‘retention’” (emphasis added, p. 25).
(8)
notes that as a subject focuses on an object, it encounters the “otherness” of
the object. But why is this definition necessary? During perception, there must
be an initial moment when the subject becomes aware of perceiving the object.
However, it is hard to exactly define when this perception begins. It must
occur on a subliminal level at first. But even if we could pinpoint the
biological timing that this subliminal processing begins, it is unclear how
much time should pass from that timing. For instance, suppose that the
subliminal processing begins at timing “X.” But does this mean that perception
begins exactly when the clock hits “X”? Wouldn’t at least some time need to
pass after that point for perception to fully occur? Specifically, shouldn’t we
say that initial perception occurs over the time span from X to X + ẟ, however
small “ẟ” might be? In other words, perception requires that there be a time
span rather than an exact singular timing coordinate. Although we cannot be
certain about the exact numerical value of ẟ, we can conceptually understand
that perception begins as the subject consciously or subconsciously becomes
aware of the object’s otherness.
In
(9), note that perception begins as awareness “occurs to focus on the
something.” In other words, the subject’s perception of the physical may be
purely accidental regardless of the subject’s intention. In this sense, the
spatiotemporal form of the physical is revealed as external to the subject.
This externalization happens because the continuity of its spatiotemporal form is
mapped onto the continuity of the subject’s awareness (but not exactly
on a one-on-one basis). Subsequently, the perception proceeds as the
spatiotemporal form manifests by aligning with the retention held by the
awareness. In other words, the image of the spatiotemporally continuous external form is continuously held in a temporal manner.
Based
on the nine definitions, let us examine more closely the relationship between
the mental and the physical.
3.
Ontology of Continuity
If everything is physical, it could exist without
the mental. After all, it is logically possible that there is a world where the
physical exists but the mental does not. The material universe has existed
since long before the human species, so that is plausible. But is it also
possible that, in all conceivable worlds, the physical exists while the mental
does not? This presents another valid logical possibility. This idea can be expanded
as follows.
Physicalists’ view:
From a vantage point outside all the conceivable
worlds, it is possible that the physical exists without
the mental having to exist in those worlds, because the ontology of the
physical (whose essence is continuity) is self-sufficient.
However,
this view raises one question. Definition (1) states that the physical lacks
awareness and has no first-person perspective. Thus, it lacks the
self-sufficiency to exhibit its spatiotemporal continuity. So how can it be
established that the physical exists in its spatiotemporal form in those worlds?
Perhaps, its continuity exists only in potential? To ensure the actual
existence of the physical, idealists (who believe that the mental takes
ontological precedence over the physical) might respond as follows.
Idealists’
view:
From
a vantage point outside all the
conceivable worlds, it is possible that the physical exists without the
mental having to exist in those worlds, because the continuity of the physical
is materialized by the mental that occupies the vantage point. The very fact
that the physical may exist on its own is entirely due to the presence of a
hypothetical being that stipulates it as such.
In
other words, the supposed self-sufficiency of the physical rests upon the
metaphysical existence of the mental. This mental must be something greater
than our mind. Our mind is finite and cannot capture the full continuity of the
physical. Simply put, our perceptions do not fully represent the physical. For
instance, our cognitive system filters out much of the available information
when observing an object. If it processed every bit of information, this would place
a huge load on our brain. That would be inefficient from an evolutionary
viewpoint.
But
why would physical continuity need to be perceived for the physical to exist?
Also, even if there is no being that actually perceives its continuity, this might
not matter because the laws of physics fully describe its “continuity” (again,
this is not mathematical continuity). For instance, Meillassoux (2008)
maintains that “the mathematizable properties of [an] object are exempt from
the constraint of a [subject’s] relation [to the world], and that they are
effectively in the object in the way in which I conceive them, whether I am in
relation with this object or not” (p. 3). Meanwhile, Žižek (2012) notes that
“even in the sphere of pure conceptual reasoning, the succession of moves does
not work as an atemporal chain of consequences” (p. 629). The laws of physics
are expressed through mathematical equations and understood through conceptual
reasoning. Without a mental being to engage in such reasoning, why would the
equations have to exist? This suggests that the universe may require some form
of mental element.
Does
this idea sound too mystical? Perhaps, but it may not be far removed from the
belief in the self-sufficiency of the physical. In fact, this self-sufficiency
can be interpreted as the actualization, through some form of mentality, of its
potential to exist in its continuity. Whether or not they agree with this idea,
physicalists must admit that their stance is inherently metaphysical. In
any case, we can argue that continuity,
as an ontological construct, connects between the mental and physical.
Specifically, the mental perceives the continuity of the physical in its
independent form, while the physical exists in its continuity due to the
metaphysical presence of the mental. Let us call this an “ontology of
continuity” thesis. This will be discussed in the context of the mind-body
problem. But before then, we will first examine several empirical studies from
brain science.
4. Features of Our Mind
Our
mind is believed to have the following features.
(A)
The conscious is an immediately present portion of the mind, which experiences
“nowness,” during which awareness at the beginning of the nowness is continuously
retained, along with the other intermediate occasions of awareness, up to
awareness at the end of the nowness.
(B)
The subconscious is a non-immediately present portion of the mind, which
organizes/modifies/integrates information in the background.
(C)
Perception, judgment, and emotion -- which are subjective experiences -- occur
on both conscious and subconscious levels, entirely dependent on corresponding
neural activities at all times.
(D)
In response to the subjective experiences, another neural activity takes place
to encode and store their information in the memory.
(E)
The mind differs from artificial intelligence (AI), which continuously appears,
from the viewpoint of the conscious, to process information under design rather
than processing information based on the sense of continuity.
Let
us examine (A) more closely. According to Wang et al. (2015), “temporal perception
is implemented in a ‘time window’ of approximately 3 s which we experience as
‘present’” (p. 405). However, 3 seconds is too long to suggest that there is
only a single instance of “awareness” within that period. According to Rayner
(1998), “[w]hen we read, look at a scene, or search for an object, we
continually make eye movements called saccades,”
between which “our eyes remain relatively still during fixations for about 200 – 300 ms” (p. 373). When reading a text,
“new information is acquired from the text only during fixations” (p. 378).
This shows that we experience multiple occasions of awareness in the present
moment.
With
regard to (B), Luo et al. (2024) note that when the brain is at rest, “the
Default Mode Network (DMN) is activated” (p. 1). Specifically, “neural
activities such as beta wave rhythm regulation, ‘subconscious’ divergence thinking mode initiation, hippocampal
function, and neural replay occur during default mode” (emphasis added, p. 1). Their
research suggests that the subconscious portion of our mind works to organize
the information learned through conscious training even when we are not working
on it.
Now
let us turn to (C). When the conscious perceives objects, what parts of the
brain work? Rowe et al. (2024) discuss the roles of the prefrontal cortex (PFC)
and “posterior cortical areas” (p. 284). Specifically, “[o]ne family of the
theories proposes that the PFC is necessary for perception,” while the other
“postulates that the PFC is not necessary and that other areas (e.g., posterior
cortical areas) are more important for conscious perception” (p. 284). Rowe et
al. claim that their observations “provide partial support for both posterior
and prefrontal theories of consciousness but do not provide strong support for
either on their own” (p. 296). This likely suggests that conscious perception
is a distributed process that involves both of them. Additionally, the PFC is
known for its crucial role in our conscious judgment-making.
Perception
occurs on a subconscious level as well. Dehaene et al. (2006) describe
“subliminal processing” as “a condition of information inaccessibility where
bottom-up activation is insufficient to trigger a large-scale reverberating
state in a global network of neurons with long range axons” (p. 206). Even if
some sensory information was received, a person may not be aware of it because
the corresponding input was too weak. For instance, if a person is presented
with a word but it is immediately “masked” by another visual stimulus (e.g.,
random letters or shapes), she may not be consciously aware of seeing the word.
Nonetheless, it can still be processed at a subliminal level. This indicates
subconscious-level perception. Judgment, too, can occur on a subconscious
level. Yin and Knowlton (2006) state that “intentional, goal-directed actions”
“often proceed automatically, as habitual responses to antecedent stimuli” (p.
464). They note that the “distinct networks involving the basal ganglia are the
neural implementations of actions and habits.” The basal ganglia is a crucial
organ in the brain that helps to make spontaneous judgments through habits.
Although their study focuses on habitual decision-making that bypasses
conscious control, it serves as an example of how subconscious judgments are
formed.
Regarding
(D), the hippocampus plays an important role in remembering subjective
experiences. According to Frankland and Bontempi (2005), “the central tenet of
most contemporary views of system consolidation” in brain science suggests that
“the hippocampus functions as a temporary store for new information, but
permanent storage depends on a broadly distributed cortical network” (p. 119).
While the PFC is involved in realization of our subjective experiences, the
hippocampus stores the neural representations of the subjective content before
they are consolidated into long-term memory in the cortex. Meanwhile, the short-term
memory that the conscious relies on is called a “working memory.” Baddeley
(2003) says, “the concept of working memory proposes that a dedicated system
maintains and stores information in the short term, and that this system
underlies human thought processes. Current views of working memory involve a
central executive” (p. 829). Although the exact mechanism of the working memory
is not yet fully understood, the “central executive … is likely to engage
multiple brain regions in a functionally coherent network, including
dorsolateral prefrontal cortex” (p. 836).
In
(E), what does it mean that AI only “continuously appears” to process
information? Today, the most prominent AI systems are Large Language Models
(LLM). Bender et al. (2021) say: “Contrary to how it may seem when we observe
its output, an LM is a system for haphazardly stitching together sequences of
linguistic forms it has observed in its vast training data, according to
probabilistic information about how they combine, but without any reference to meaning: a stochastic parrot” (pp.
616-617). Yet, skeptics note that the meaning of “meaning” is inherently
ambiguous. Also, when considering that human language is fluid and
context-dependent, it may be unreasonable to expect LLMs to possess a single,
unified understanding of meaning. Moreover, there may be no true
“understanding” of meaning. From a purely functional viewpoint, if LLMs perform
well enough in real-world tasks, they may have no qualitative difference from
human reasoning. In addition, every error they might make could be justified
when considering human fallibility.
The
power of LLMs is undeniable. Since they have been trained on vast amounts of
data (accumulated through collective human efforts) and can connect information
at a speed far beyond human capacity, they can provide information or even
novel insights that nobody can individually. But they may still fall short of
reaching a level of understanding where “retention” takes place. Without
retention, there can be no perspective from which to make judgments. Any
“first-person perspective” held by LLMs is arguably non-existent. Furthermore,
any information synthesis performed on their part may subtly differ from ours
because they do not rely on the sense of continuity. This could result in a
qualitative difference between their response and ours. But how can this
difference be shown?
While
discussing a difference between human and machine intelligence, Lee (2024) somewhat
abruptly notes that time traveling to the past is “philosophically worth
considering, even though it is unlikely to materialize in reality” (p. 21). In
his view, “[i]f a human agent in the past received our knowledge of her history
(which would be regarded as a form of future knowledge for her), she would
generate a non-trivial response to it. However, a machine agent would not be
able to” (p. 27). This is only presented as a pure metaphysical possibility,
because it violates the principle of causality in physics. Nevertheless, suppose
the impossible. Say, the human agent came to know about her future. Then, despite
there being no causal link between her distant past and her new found knowledge,
she would be able to provide a non-trivial response to it. For example, she
might ask: “Whatever action I take right now, was that also predetermined?” (p.
24). This illustrates the continuity of her subjective experience, as she can
synthesize her “current” knowledge of her state with the “future” knowledge of
her in a continuous way.
On
the other hand, AI only operates under a set of specific rules under a
mechanical architecture, even if it employs “stochastic” reasoning. Thus, it
would be unable to provide a non-trivial response to knowledge of its future. This
does not mean that the AI would not respond in a “continuous” way. It certainly
could. From a third-person perspective (i.e., our perspective), the way that AI
produces its response appears continuous, because the AI is part of the
physical. However, AI lacks anything we might call non-physical, e.g., a first-person
perspective. As a result, it experiences no continuity in information
processing. Accordingly, the content of its potential response would be
“obvious,” producing something like “The seminar tires me” (p. 22). Although
this metaphysical difference between the two cannot be directly observed in our
empirical world, it remains latent in their operational difference.
Next,
we will explore the above features in relation to two major challenges in the
mind-body problem: causal overdetermination and physical causal closure. Following
this, we will discuss two models of our mind that meet this challenge.
5. New Supervenience
Model
(1)
Causal Overdetermination
John
Searle claims that “[m]ental phenomena are caused by neurophysiological
processes in the brain and are themselves features of the brain” (Kim, 1995, p.
189). However, Kim counters that it does not provide a “simple solution” to the
mind-body problem (p. 189). Kim questions Searle’s rationale for rejecting
reductionism while embracing supervenience. But what exactly is supervenience?
Kim
(1998) explains: “Mental properties supervene
on physical properties, in that necessarily any two things (in the same or
different possible worlds) indiscernible in all physical properties are
indiscernible in mental respects” (p. 10). This means that there can be no
change in the mental unless there is any corresponding change in the physical. The
supervenience of “phenomenal properties” on the physical has “nomological
necessity” (i.e., necessary by virtue of the natural laws of the universe).
Kim
does not believe that one can reject reductionism if she accepts supervenience.
His position is based on causal overdetermination. Kim (1995, p. 193) explains
it as follows:
Let:
M
= mental property
B
= biological property
Mental
event = instantiation of M = instantiation of B
Assumption:
M has causal powers to cause other properties to be instantiated.
Case
1: The property that M can cause to be instantiated is itself a mental property
(M*). (Same-level causation)
Case
2: The property that M can cause to be instantiated is a biological property.
(Downward causation)
Observations:
M*
is also caused by some underlying biological property (B*).
Thus,
M* has two distinct sufficient causes (i.e., M and B*).
In
other words, M* is causally overdetermined.
Kim
(1998) ironically describes this as a “bless[ing] with an overabundance of
causes” (p. 43). He highlights that an “antireductive physicalist who wants to
remain a mental realist ... must give an account of how the mental cause and
the physical cause of one and the same event are related to each other” (p.
37). Since there is no viable solution to this problem, Kim turns to reductive
physicalism.
He observes that “[r]eductive physicalism saves the mental but only as a part
of the physical” (p. 120). Ultimately, he concludes: “To think that one can be
a serious physicalist and at the same time enjoy the company of things and
phenomenon that are nonphysical ... is an idle dream.” Kim does not seem to
deny the reality of subjective experience. It is a brute fact that it exists.
Qualia (i.e., the “what it feels like” aspect of our subject experience) is
undeniable. But why does it exist? Is the mental just an epiphenomenal outcome (i.e.,
a byproduct of the physical brain with no causal power)? This will be discussed
in more detail in the following sub-section.
(2)
Neuro-Subjective Interactive (NSI) Model
This
paper argues that subjective experience is crucial for generating sophisticated
information for the brain. Without subjective experience, the brain would only
receive the crudest form of information and fail to acquire complex thinking
abilities. As noted earlier, human intelligence is set apart from AI due to its
ability to continuously synthesize
information to output a high-level judgment. This synthesis is possible only when
an agent can retain information up to
reaching a final judgment. However, Kim’s core implication is that, since every
subjective experience is ultimately neuronal in the physical sense, the brain
may work perfectly well without them. But this is not the case. To clarify, let
us revisit Features (C) and (D).
According
to (C), subjective experience depends entirely on its corresponding neural activity
at all times. (D) alleges that another neural activity takes place to encode
and store the content of the subjective experience. Previously, we saw that the
conscious relies on the “working memory.” For instance, understanding a sentence
requires that we retain our understanding of a subject word
within the sentence until we recognize its predicate. This is impossible without
memory.
The
implication is that when our conscious is working, it relies on multiple neural
processes. Specifically, one type of neural activity generates our subjective
experience. Simultaneously, another neural process takes place to carry
information about the content of the subjective experience and provide it to
the existing neural activity that the subjective experience supervenes on. This
interaction enables the sense of awareness. Additionally, information may be
retrieved through neural pathways from the long-term memory to inform and guide
the current neural activity. These processes establish a feedback loop, which
enables the subjective experience to proceed to a subsequent stage while
supervening on a corresponding neural activity. This is what the paper refers
to as a neuro-subjective interactive
(NSI) model. See the figure below.
[Figure
1: Neuro-Subjective Interactive (NSI) Model]
N1,
N2, and N3 stand for neural activities that subjective
experiences S1, S2, and S3 supervene on. These
individual subjective experiences are assumed to be as simplistic as possible.
In other words, no single subjective experience constitutes a complex thinking
activity that unfolds over a prolonged time.
ST1,
ST2, and ST3 represent the short-term memory encoding of
S1, S2, and S3. The nature of continuity present
within the perception/judgment forming each of S1, S2,
and S3 adds sophistication to the information. This information is
fed back in short-term neural form to N1, N2, and N3.
This helps to retain the sense of awareness.
LM
stands for the long-term memory, which also receives the information from ST1,
ST2, and ST3. Relevant information may be provided from LM
to N1, N2, and N3. This enriches the
subjective experiences.
Without
the influence of subjective experiences, the pattern of neural activities across
the brain, as we understand them today, would look quite different. It is
possible that the neural activities are worked out through the mediating role
of subjective experiences. These experiences provide sophisticated information
to the neural that spontaneous reflexes or AIs cannot. This addresses Kim’s
concern that the mental may be epiphenomenal. It also overcomes causal
overdetermination.
Conventionally,
we assume that the mental entirely supervenes on the physical. This is valid. Yet,
the traditional supervenience model may create an impression of a rigid
separation between the mental and physical. In contrast, our model considers
the subjective experience as a component of the tetrad: N – S – ST – LM. This
as a whole constitutes the biological mental. In other words, both the
subjective and neural, which are believed to belong in different realms, are
the critical components of human mentality (not the mentality assumed by
idealists). As such, rather than placing a strict hierarchical distinction
between the physical and the mental, the NSI model suggests that our mentality be understood to comprise both the subjective experience and its
physical basis. In other words, the brain is a kind of biological
information-processing machine that operates through the subjective as well as
the neural. Consider the following scenario.
A person sees a pigeon on the street (S1).
The perception supervenes on the neural (N1). The perception is
immediately encoded in neural form (ST1) and fed back to the neural
(N1). This leads to the sense of awareness during which the
perception is happening. At the same time, ST1 triggers the
long-term memory (LM) to provide related information to the neural (N1).
(This triggering process would not have occurred in the same way without the
subjective experience (S1), which integrates the sensory input into a continuous spatiotemporal perception of
the pigeon.) Due to the triggering, her vague memory of reading a news article on
the germs spread by pigeons comes up. This can be either a subconscious process
or a process where the memory surfaces on a conscious level. Let us assume that
it is subconscious. This subconscious processing can trigger a sense of disgust
with the pigeon. Then, it guides the neural (N1) to proceed to a new
neural form (N2). Since N2 is an extension from N1,
the influence of N1 remains in N2. This retains the sense
of continuity from N1 to N2.
The new neural (N2) can now generate a subjective experience (S2)
of abhorrence of the pigeon. This experience is an emotional one. The
abhorrence is transformed into neural information (ST2). Then, this
information is fed back to N2, together with information from LM suggesting
that it is preferable to create a distance from the object of abhorrence. All
of this leads to N3. By supervening on N3, she makes a
judgment that she should walk away. As information on this judgment is
transferred through ST3 to N3, together with an
instruction to run from LT, she may proceed to a subjective state of physically
running (i.e., S4 supervening on N4).
As
shown above, the NSI model overcomes a limitation of non-reductive
physicalism
(i.e., causal overdetermination) by
assigning a “functional” role to the subjective in the context of neural
workings. This also naturally resolves a limitation of reductive physicalism
propounded by Kim. Reductive physicalism cannot explain the role that the
subjective plays within neural processes. But the above model does. That is,
the subjective provides information to the neural and influences its activity.
However,
the model raises concerns. First, it does not explain how the subjective arises
from the physical, nor how the content of subject experiences is encoded into
neural form. Second, subjective experiences seem to have only a passive role in
the neural processing. They appear to function only as intermediaries.
As
for the first concern, note that the principles of supervenience between the
biological-chemical-physical are equally elusive. But still, we may try a
metaphysical resolution. Section 3 proposed an “ontology of continuity” thesis
in order to bridge the mental and physical. This approach shares some sympathy
with what Chalmers (1996) calls “psychophysical laws” (p. 127). They specify
“how phenomenal (or protophenomenal) properties depend on physical properties.”
In addition, they “will not interfere with physical laws; physical laws already
form a closed system. Instead, they will be supervenience
laws, telling us how experience
arises from physical processes.” Since “the dependence of experience on the
physical cannot be derived from physical laws, so any final theory must include
laws of this variety.” Although the conception of psychophysical laws remains
speculative, it provides a tentative holistic framework. The ontology of
continuity can provide a basis for the compatibility between the physical and
mental. This can justify why psychophysical laws may be possible.
Then,
what about the “encoding” process? Empirically, it is well known that events in
our lives mold our brain structure. For instance, the deep traumas of war may
substantially “rewire” the victims’ brains. However, it is also hard to know what
enables this transition from the subjective to the neural encoding. Given the
upward and downward
transitions between the subjective and neurons, we might have to add that they
establish a dialectical relationship where one cannot exist without the other.
The
second concern is addressed through a derivative version of the NSI model in
the next sub-section. However, before illustrating the model, a brief mention
should be made on the relationship between perception and awareness. In
Definition (9), perception is defined based on awareness. However, in our
evolutionary history, it is more likely that perception preceded awareness. The
initial rudimentary forms of life on earth most certainly relied on automatic,
spontaneous reflexes rather than conscious thinking. This would have provided
an evolutionary advantage of quickly detecting prey or avoiding enemies. This
cumulative process of building upon the history of sensory experiences likely
led to a vague sense of self. As life forms grew more and more sophisticated,
along with the development of memory organs, this sense of self would have
become more substantial. The perceptive function powered by this sense of self
enabled more sophisticated “judgments” for survival. In other words, instead of
purely relying on automatic reflexes, they began to develop a more complex
understanding of their environmental circumstances through “awareness.” All
this culminated in the emergence of homo
sapiens, which acquired the ability to engage in reasoning by abstracting
from perceptions, powered by both short-term and long-term memories.
(3)
NSI Model Simplified
Now,
in the NSI model, suppose that the respective time lapses between N1,
N2, and N3; and
ST1, ST2, and ST3 became incredibly short.
Then, it would look like they were almost one and the same. This is illustrated
as follows.
[Figure
2: NSI Model Simplified]
In
the figure, the subjective proceeds almost
in parallel with the neural. Without the neural, the subjective cannot unfold. It
is totally dependent on the physical. Meanwhile, the neural would not function
in the same way without subjective experiences involved. Therefore, the
subjective and neural establish a co-dependent relationship. Specifically, as
the respective lapses between N1, N2, and N3;
and ST1, ST2, and ST3 become increasingly
shorter, along with the diminishing lapses between N1, N2,
and N3, the subjective establishes continuity over these discrete
processes. This creates a mental experience.
Again, this continuity is grounded in the compatibility between the mental and
physical assured by the ontology of continuity. It proceeds on its own terms
with the neural backing it up at all times. This explanation overcomes, at
least partially, the concern that the subjective is merely passive. Although
the model as depicted in Fig. 2 does not fully illustrate an active, agential
aspect of the human psyche, it is somewhat close to it. Its difference from the
NSI model lies in approximating the agential aspect of the human mind.
The
next section discusses potential critiques of the models and their underlying
basis.
6. Potential Critiques and
Other Views
(1) Physical Causal
Closure
Kim
might question the NSI model by invoking “physical causal closure.” Kim (1998)
states:
“One
way of stating the principle of physical causal closure of the physical domain
is this: If you pick any physical event and trace out its causal ancestry or posterity,
that will never take you outside the physical domain. That is, no causal chain
will take you outside the physical domain. That is, no causal chain will ever
cross the boundary between the physical and the nonphysical. … If you reject
this principle, you are ipso facto rejecting the in-principle completability of
physics -- that is, the possibility of a complete and comprehensive physical
theory of all physical phenomena” (p. 40).
Meanwhile,
the NSI model posits that the subjective experience, as a non-physical cause,
influences, through a subsequent neural representation of the subjective
experience, an existing neural activity on which the subjective experience
supervenes. Technically speaking, this violates the physical causal closure
principle. However, in Section 3, we already discussed a limitation of
physicalism. Physicalism cannot justify itself. It does not justify the vantage
point from which it is determined that the physical can exist alone in all
conceivable worlds. The continuity of the physical cannot be established unless
it relies on some form of mental element. When physicists assert that every
physical phenomenon should be explained through the laws of physics, who is
saying it? Also, physical causal closure is a conceptual tool to be employed when observing physical phenomena.
This tool may have limits when applied to explaining our mentality. Similarly,
Chalmers (1996) notes: “The laws and causal relations themselves are posited to
explain existing physical phenomena, namely the manifold regularities present in
nature, whereas consciousness is a brute explanandum” (p. 86).
Admittedly,
the brain is a physical entity that is subject to the laws of physics.
Nevertheless, our capacity for reasoning demands more explanation than physical
laws. Instead of totally subjugating our mentality to the physical realm, it is
preferable to take a more holistic view that looks beyond physical causal
closure. This is what the NSI model attempts to do.
(2) Other Views
This
paper might be criticized for being substance dualist. In the classical
sense, substance dualism is Cartesian dualism. It says that the mind and body
are separate substances, but direct interaction can be achieved between them. Specifically,
Rodrigues (2014) distinguishes between “strong substance dualism” and “moderate
substance dualism” (p. 202). The former states that “[s]ouls are immaterial
objects whose properties are mental and they are distinct and independent of
the body and the brain,” while the latter says that the “souls” are “not
independent of the body and the brain.” Rodrigues defines soul as “a capacity
for mentality” (p. 205). The NSI model aligns better with the moderate version.
Still, there is a subtle difference. The NSI model highlights that both the
subjective and the neural are the critical components of our mentality. Then, according
to the model, soul should be partially physical. Furthermore, although the
model assumes a leap between the subjective and neural, it does not state that
our mentality directly interacts with the physical. Its workings are more
intricate than naïve substance dualism.
Nevertheless,
the ontology of continuity thesis may be dualistic, although it focuses more on
compatibility between the two. It stipulates that the physical exists only when
the existence of mentality is ensured in a metaphysical sense. This
metaphysical notion might be criticized for being unclear. It could mean,
roughly, that mentality (such as ours) has the potentiality to emerge through
a physical means or that the universe as a whole has some form of mentality
that our finite mind cannot grasp. This is essentially an idealistic stance.
Meanwhile,
libertarianism may be viewed as an idealized version of our second
model. “According to libertarian accounts, at least on certain occasions people
can be genuinely free agents. This means that sometimes they can be sources of
their actions, as opposed to mere witnesses or bystanders of them” (Morales,
2023, p. 6). Unfortunately, the second model does not deliver on its aim to
fully illustrate this libertarian notion. As noted earlier, it only
approximates the agential aspect of our mind. The NSI model, too, is limited to
conceptualizing our mentality as a biological information processing mechanism.
Another
interesting view is non-reductive monism. This suggests that the
physical is the only fundamental type of substance in the universe. But mental properties do exist. They depend on the
physical. Nonetheless, they are not reducible into physical properties. This
position is defended by MacDonald & MacDonald (2006). They believe that
“mental properties supervene on physical ones” and conclude that the “mental
properties … are not themselves constitutive properties of the events …, but
rather, supervene on those events’ physical, constitutive properties” (p. 561).
In their view, “mental properties of events could be causally relevant
to the effects their instancings bring about” (p. 543). But they are not
“causally efficacious.” Although their distinction between causal relevance and
efficacy may conceptually bypass causal overdetermination, this does not seem
to convincingly overcome epiphenomenalism. Their efforts to assign a special
characteristic to our mentality end up prioritizing physical causality in order
to avoid causing trouble with Kim’s physical causal closure. In contrast, the
NSI model adamantly acknowledges subjective experiences’ distinction over the physical
while placing them within the context of brain functioning.
Consequently,
the NSI model may be viewed as an idealist-influenced revisionary version of
non-reductive physicalism. While traditional non-reductive physicalism primarily
explains that the mental supervenes on the physical, the model expands on this
by describing mentality as a combination of neural (physical) processes and a
subjective element that supervenes on part
of these processes. Specifically, neural activity functions to construct a
coherent picture of the self and the external world in terms of their
continuity. It generates a qualitatively different subjective experience
through which the existing neural activity is reorganized by referring to
itself and being informed on the past by the long-term memory.
7. Conclusion
The
major ideas of the paper are summarized below.
(I)
Ontology of Continuity
Continuity,
as an ontological construct, connects between the mental and the physical, as
the mental perceives the continuity of the physical in its independent form,
while the physical exists in its continuity due to the metaphysical presence of
the mental.
(II)
Consciousness
By
entirely relying on neural activity, through the consecutive steps of nowness
that depend on the short-term memory, the conscious portion of our mind (i)
perceives the physical world and (ii) makes judgments by building upon
abstractions from the perceptions, while the subconscious dynamically
modifies/integrates/organizes the information, which is accumulated through the
perceptions and judgments in the long-term memory, in order to feed it back to
the conscious when needed.
(III)
Neuro-Subjective Interactive (NSI) Model
Subjective
experience consistently supervenes on
the neural, with its continuity enhancing the complexity of information to be provided to the neural. Specifically,
this subjective content is continuously encoded in the short-term memory and
fed back to the neural, sustaining the sense of awareness. The information
retrieved from long-term memory contributes to the complexity of judgments
formed through subjective experience. The compatibility between the subjective
and the neural is grounded in the ontology of continuity thesis.
Through
the above ideas, the paper sought to overcome physicalism. At the same time, it
made efforts to resolve causal overdetermination and physical causal closure.
Although the paper’s conceptions do not definitively solve the problems in the
contemporary mind-body problem debate, the author hopes that they build a
meaningful extension to inspire further thoughts on the issue.
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All this perception
and judgment take place through relevant neural activities. According to Tononi
and Koch (2015), the “neural correlates of consciousness (NCC) have been
defined as the minimal neural mechanisms that are jointly sufficient for any
one conscious percept, thought or memory” (p. 2). “Every experience will have
an associated NCC: one for seeing a red patch, another one for hearing a high
C.”
This is the view that
the mind is ultimately reducible to the physical. Regarding reducibility, Stoljar
(2022) states: “Reductionism is true iff for each mental predicate F,
there is a physical predicate G such that a sentence of the
form ‘x is F iff x is G’
is analytically true” (emphasis
added, Section 3.1). Simply put, the mental can be explained fully through a
mere conceptual analysis of physical truths. But is it obviously true that the
mental logically follows from the physical? We may boldly claim that if that is
true, it is only because the physical is
what the mental perceives of and abstracts from reality.
Our initial recognition
of the subject word occurs as we come to “focus” on it as in Definition (8) in
Section 2. That is, we encounter its “otherness.” But when does real
comprehension of the subject word begin? It likely begins when information is
retrieved from the long-term memory and synthesized with the information from
the recognition. The comprehension of the subject word is almost subconscious,
as it unfolds spontaneously.
This view says that
while mental states are fully dependent on physical states, they cannot be
fully reduced to physical states. The distinction between non-reductive
physicalism and emergentism is often
blurred. For details, see Barnes (2012, pp. 897-899).
The downward
transition subtly differs from “downward causation.” Downward causation
suggests that higher-level mental phenomena influence lower-level physical
processes. Meanwhile, the downward transition is a process where the content of
a subjective experience is transformed into neural form to be used by a neural
activity that is generating the subjective experience. Thus, in our model, the
downward causation is to be understood as a process where N1, N2,
and N3 affect themselves through subjective experiences while the
long-term memory is influencing them in the background.
A stronger version of
this view is shared by Hanna (2006): “Things can exist without existing human
persons, and in fact did so for millions of years before we came along. But things could not have existed unless it were
really possible for us to come along” (emphasis added) (p. 32).
