Biological Naturalism states that consciousness is a higher level function of the human brain's physical capabilities.
Biological naturalism is a theory about, among other things, the relationship between consciousness and body (i.e. brain), and hence an approach to the mind–body problem. It was first proposed by the philosopher John Searle in 1980 and is defined by two main theses: 1) all mental phenomena from pains, tickles, and itches to the most abstruse thoughts are caused by lower-level neurobiological processes in the brain; and 2) mental phenomena are higher-level features of the brain.
This entails that the brain has the right causal powers to produce intentionality. However, Searle's biological naturalism does not entail that brains and only
brains can cause consciousness. Searle is careful to point out that
while it appears to be the case that certain brain functions are
sufficient for producing conscious states, our current state of
neurobiological knowledge prevents us from concluding that they are
necessary for producing consciousness. In his own words:
"The fact that brain processes cause consciousness does not imply
that only brains can be conscious. The brain is a biological machine,
and we might build an artificial machine that was conscious; just as the
heart is a machine, and we have built artificial hearts. Because we do
not know exactly how the brain does it we are not yet in a position to
know how to do it artificially." (Biological Naturalism, 2004)
Overview
John Searle
Searle denies Cartesian dualism, the idea that the mind is a separate kind of substance to the body, as this contradicts our entire understanding of physics, and unlike Descartes, he does not bring God
into the problem. Indeed, Searle denies any kind of dualism, the
traditional alternative to monism, claiming the distinction is a
mistake. He rejects the idea that because the mind is not objectively
viewable, it does not fall under the rubric of physics.
Searle believes that consciousness "is a real part of the real world and it cannot be eliminated in favor of, or reduced to, something else"[1] whether that something else is a neurological state of the brain or a computer program. He contends, for example, that the software known as Deep Blueknows nothing about chess. He also believes that consciousness is both a cause of events in the body and a response to events in the body.
On the other hand, Searle doesn't treat consciousness as a ghost in the machine.
He treats it, rather, as a state of the brain. The causal interaction
of mind and brain can be described thus in naturalistic terms: Events at
the micro-level (perhaps at that of individual neurons)
cause consciousness. Changes at the macro-level (the whole brain)
constitute consciousness. Micro-changes cause and then are impacted by
holistic changes, in much the same way that individual football players
cause a team (as a whole) to win games, causing the individuals to gain
confidence from the knowledge that they are part of a winning team.
He articulates this distinction by pointing out that the common
philosophical term 'reducible' is ambiguous. Searle contends that
consciousness is "causally reducible" to brain processes without being
"ontologically reducible". He hopes that making this distinction will
allow him to escape the traditional dilemma between reductive materialism
and substance dualism; he affirms the essentially physical nature of
the universe by asserting that consciousness is completely caused by and
realized in the brain, but also doesn't deny what he takes to be the
obvious facts that humans really are conscious, and that conscious
states have an essentially first-person nature.
It can be tempting to see the theory as a kind of property dualism,
since, in Searle's view, a person's mental properties are categorically
different from his or her micro-physical properties. The latter have
"third-person ontology"
whereas the former have "first-person ontology." Micro-structure is
accessible objectively by any number of people, as when several brain
surgeons inspect a patient's cerebral hemispheres. But pain or desire or belief
are accessible subjectively by the person who has the pain or desire or
belief, and no one else has that mode of access. However, Searle holds
mental properties to be a species of physical property—ones with
first-person ontology. So this sets his view apart from a dualism of
physical and non-physical properties. His mental properties are
putatively physical.
Criticism
There have been several criticisms of Searle's idea of biological naturalism.
Jerry Fodor suggests that Searle gives us no account at all of exactly why he believes that a biochemistry like, or similar to, that of the human brain is indispensable for intentionality.
Fodor thinks that it seems much more plausible to suppose that it is
the way in which an organism (or any other system for that matter) is
connected to its environment that is indispensable in the explanation of
intentionality. It is easier to see "how the fact that my thought is
causally connected to a tree might bear on its being a thought about a
tree. But it's hard to imagine how the fact that (to put it crudely) my
thought is made out of hydrocarbons could matter, except on the unlikely
hypothesis that only hydrocarbons can be causally connected to trees in
the way that brains are." [2]
John Haugeland
takes on the central notion of some set of special "right causal
powers" that Searle attributes to the biochemistry of the human brain.
He asks us to imagine a concrete situation in which the "right" causal
powers are those that our neurons have to reciprocally stimulate one
another. In this case, silicon-based alien life forms can be intelligent
just in case they have these "right" causal powers; i.e. they possess
neurons with synaptics connections that have the power to reciprocally
stimulate each other. Then we can take any speaker of the Chinese
language and cover his neurons in some sort of wrapper which prevents
them from being influenced by neurotransmitters and, hence, from having
the right causal powers. At this point, "Searle's demon" (an English
speaking nanobot, perhaps) sees what is happening and intervenes: he
sees through the covering and determines which neurons would have been
stimulated and which not and proceeds to stimulate the appropriate
neurons and shut down the others himself. The experimental subject's
behavior is unaffected. He continues to speak perfect Chinese as before
the operation but now the causal powers of his neurotransmitters have
been replaced by someone who does not understand the Chinese language.
The point is generalizable: for any causal powers, it will always be
possible to hypothetically replace them with some sort of Searlian demon
which will carry out the operations mechanically. His conclusion is
that Searle's is necessarily a dualistic view of the nature of causal
powers, "not intrinsically connected with the actual powers of physical
objects." [3]
Searle himself does not rule out the possibility for alternate
arrangements of matter bringing forth consciousness other than
biological brains. He also disputes that Biological naturalism is
dualistic in nature in a brief essay entitled "Why I Am Not a Property Dualist".
A phrenological mapping of the brain – phrenology
was among the first attempts to correlate mental functions with
specific parts of the brain although it is now largely discredited.
Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are addressed, such as the hard problem of consciousness and the nature of particular mental states. Aspects of the mind that are studied include mental events, mental functions, mental properties, consciousness, the ontology of the mind, the nature of thought, and the relationship of the mind to the body.
Dualism and monism are the two central schools of thought on the mind–body problem, although nuanced views have arisen that do not fit one or the other category neatly.
Dualism finds its entry into Western philosophy thanks to René Descartes in the 17th century. Substance dualists like Descartes argue that the mind is an independently existing substance, whereas property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.
Monism is the position that mind and body are ontologically indiscernible entities (not dependent substances). This view was first advocated in Western philosophy by Parmenides in the 5th century BCE and was later espoused by the 17th-century rationalistBaruch Spinoza. Physicalists
argue that only entities postulated by physical theory exist, and that
mental processes will eventually be explained in terms of these entities
as physical theory continues to evolve. Physicalists maintain various
positions on the prospects of reducing mental properties to physical
properties (many of whom adopt compatible forms of property dualism), and the ontological status of such mental properties remains unclear. Idealists
maintain that the mind is all that exists and that the external world
is either mental itself, or an illusion created by the mind. Neutral monists such as Ernst Mach and William James
argue that events in the world can be thought of as either mental
(psychological) or physical depending on the network of relationships
into which they enter, and dual-aspect monists such as Spinoza
adhere to the position that there is some other, neutral substance, and
that both matter and mind are properties of this unknown substance. The
most common monisms in the 20th and 21st centuries have all been
variations of physicalism; these positions include behaviorism, the type identity theory, anomalous monism and functionalism.
Most modern philosophers of mind adopt either a reductive physicalist
or non-reductive physicalist position, maintaining in their different
ways that the mind is not something separate from the body. These approaches have been particularly influential in the sciences, especially in the fields of sociobiology, computer science (specifically, artificial intelligence), evolutionary psychology and the various neurosciences.
Reductive physicalists assert that all mental states and properties
will eventually be explained by scientific accounts of physiological
processes and states. Non-reductive physicalists argue that although the mind is not a separate substance, mental properties supervene
on physical properties, or that the predicates and vocabulary used in
mental descriptions and explanations are indispensable, and cannot be
reduced to the language and lower-level explanations of physical
science. Continued neuroscientific
progress has helped to clarify some of these issues; however, they are
far from being resolved. Modern philosophers of mind continue to ask
how the subjective qualities and the intentionality of mental states and properties can be explained in naturalistic terms.
However, a number of issues have been recognized with
non-reductive physicalism. First, it is irreconcilable with
self-identity over time. Secondly, intentional states of consciousness
do not make sense on non-reductive physicalism. Thirdly, free will is
impossible to reconcile with either reductive or non-reductive
physicalism. Fourthly, it fails to properly explain the phenomenon of
mental causation.
Mind–body problem
The mind–body problem concerns the explanation of the relationship that exists between minds, or mental processes, and bodily states or processes.
The main aim of philosophers working in this area is to determine the
nature of the mind and mental states/processes, and how—or even if—minds
are affected by and can affect the body.
Perceptual experiences depend on stimuli that arrive at our various sensory organs
from the external world, and these stimuli cause changes in our mental
states, ultimately causing us to feel a sensation, which may be pleasant
or unpleasant. Someone's desire for a slice of pizza, for example, will
tend to cause that person to move his or her body in a specific manner
and in a specific direction to obtain what he or she wants. The
question, then, is how it can be possible for conscious experiences to
arise out of a lump of gray matter endowed with nothing but
electrochemical properties.
A related problem is how someone's propositional attitudes (e.g. beliefs and desires) cause that individual's neurons to fire and muscles to contract. These comprise some of the puzzles that have confronted epistemologists and philosophers of mind from the time of René Descartes.
Dualist solutions to the mind–body problem
Dualism is a set of views about the relationship between mind and matter (or body). It begins with the claim that mental phenomena are, in some respects, non-physical. One of the earliest known formulations of mind–body dualism was expressed in the eastern Samkhya and Yoga schools of Hindu philosophy (c. 650 BCE), which divided the world into purusha (mind/spirit) and prakriti (material substance). Specifically, the Yoga Sutra of Patanjali presents an analytical approach to the nature of the mind.
In Western Philosophy, the earliest discussions of dualist ideas are in the writings of Plato who suggested that humans' intelligence (a faculty of the mind or soul) could not be identified with, or explained in terms of, their physical body. However, the best-known version of dualism is due to René Descartes (1641), and holds that the mind is a non-extended, non-physical substance, a "res cogitans". Descartes was the first to clearly identify the mind with consciousness and self-awareness,
and to distinguish this from the brain, which was the seat of
intelligence. He was therefore the first to formulate the mind–body
problem in the form in which it still exists today.
Arguments for dualism
The
most frequently used argument in favor of dualism appeals to the
common-sense intuition that conscious experience is distinct from
inanimate matter. If asked what the mind is, the average person would
usually respond by identifying it with their self, their personality, their soul,
or another related entity. They would almost certainly deny that the
mind simply is the brain, or vice versa, finding the idea that there is
just one ontological entity at play to be too mechanistic or unintelligible. Modern philosophers of mind think that these intuitions are misleading and that we critical faculties, along with empirical evidence from the sciences, should be used to examine these assumptions and determine whether there is any real basis to them.
The mental and the physical seem to have quite different, and perhaps irreconcilable, properties.
Mental events have a subjective quality, whereas physical events do
not. So, for example, one can reasonably ask what a burnt finger feels
like, or what a blue sky looks like, or what nice music sounds like to a
person. But it is meaningless, or at least odd, to ask what a surge in
the uptake of glutamate in the dorsolateral portion of the prefrontal cortex feels like.
Philosophers of mind call the subjective aspects of mental events "qualia" or "raw feels".
There are qualia involved in these mental events that seem particularly
difficult to reduce to anything physical. David Chalmers explains this
argument by stating that we could conceivably know all the objective
information about something, such as the brain states and wavelengths of
light involved with seeing the color red, but still not know something
fundamental about the situation – what it is like to see the color red.
If consciousness (the mind) can exist independently of physical
reality (the brain), one must explain how physical memories are created
concerning consciousness. Dualism must therefore explain how
consciousness affects physical reality. One possible explanation is that
of a miracle, proposed by Arnold Geulincx and Nicolas Malebranche, where all mind–body interactions require the direct intervention of God.
Another argument that has been proposed by C. S. Lewis is the Argument from Reason:
if, as monism implies, all of our thoughts are the effects of physical
causes, then we have no reason for assuming that they are also the consequent
of a reasonable ground. Knowledge, however, is apprehended by reasoning
from ground to consequent. Therefore, if monism is correct, there would
be no way of knowing this—or anything else—we could not even suppose
it, except by a fluke.
The zombie argument is based on a thought experiment proposed by Todd Moody, and developed by David Chalmers in his book The Conscious Mind.
The basic idea is that one can imagine one's body, and therefore
conceive the existence of one's body, without any conscious states being
associated with this body. Chalmers' argument is that it seems possible
that such a being could exist because all that is needed is that all
and only the things that the physical sciences describe about a zombie
must be true of it. Since none of the concepts involved in these
sciences make reference to consciousness or other mental phenomena, and
any physical entity can be by definition described scientifically via physics, the move from conceivability to possibility is not such a large one. Others such as Dennett have argued that the notion of a philosophical zombie is an incoherent, or unlikely,
concept. It has been argued under physicalism that one must either
believe that anyone including oneself might be a zombie, or that no one
can be a zombie—following from the assertion that one's own conviction
about being (or not being) a zombie is a product of the physical world
and is therefore no different from anyone else's. This argument has been
expressed by Dennett who argues that "Zombies think they are conscious,
think they have qualia, think they suffer pains—they are just 'wrong'
(according to this lamentable tradition) in ways that neither they nor
we could ever discover!"
Interactionist dualism, or simply interactionism, is the particular form of dualism first espoused by Descartes in the Meditations. In the 20th century, its major defenders have been Karl Popper and John Carew Eccles. It is the view that mental states, such as beliefs and desires, causally interact with physical states.
Descartes' argument for this position can be summarized as
follows: Seth has a clear and distinct idea of his mind as a thinking
thing that has no spatial extension (i.e., it cannot be measured in
terms of length, weight, height, and so on). He also has a clear and
distinct idea of his body as something that is spatially extended,
subject to quantification and not able to think. It follows that mind
and body are not identical because they have radically different
properties.
Seth's mental states (desires, beliefs, etc.) have causal
effects on his body and vice versa: A child touches a hot stove
(physical event) which causes pain (mental event) and makes her yell
(physical event), this in turn provokes a sense of fear and
protectiveness in the caregiver (mental event), and so on.
Descartes' argument depends on the premise that what Seth believes to be "clear and distinct" ideas in his mind are necessarily true. Many contemporary philosophers doubt this. For example, Joseph Agassi
suggests that several scientific discoveries made since the early 20th
century have undermined the idea of privileged access to one's own
ideas. Freud
claimed that a psychologically-trained observer can understand a
person's unconscious motivations better than the person himself does. Duhem has shown that a philosopher of science can know a person's methods of discovery better than that person herself does, while Malinowski
has shown that an anthropologist can know a person's customs and habits
better than the person whose customs and habits they are. He also
asserts that modern psychological experiments that cause people to see
things that are not there provide grounds for rejecting Descartes'
argument, because scientists can describe a person's perceptions better
than the person herself can.
Other forms of dualism
Four varieties of dualism. The arrows indicate the direction of the causal interactions. Occasionalism is not shown.
Psychophysical parallelism
Psychophysical parallelism, or simply parallelism,
is the view that mind and body, while having distinct ontological
statuses, do not causally influence one another. Instead, they run along
parallel paths (mind events causally interact with mind events and
brain events causally interact with brain events) and only seem to
influence each other. This view was most prominently defended by Gottfried Leibniz. Although Leibniz was an ontological monist who believed that only one type of substance, the monad,
exists in the universe, and that everything is reducible to it, he
nonetheless maintained that there was an important distinction between
"the mental" and "the physical" in terms of causation. He held that God
had arranged things in advance so that minds and bodies would be in
harmony with each other. This is known as the doctrine of pre-established harmony.
Occasionalism
Occasionalism is the view espoused by Nicholas Malebranche as well as Islamic philosophers such as Abu Hamid Muhammad ibn Muhammad al-Ghazali
that asserts that all supposedly causal relations between physical
events, or between physical and mental events, are not really causal at
all. While body and mind are different substances, causes (whether
mental or physical) are related to their effects by an act of God's
intervention on each specific occasion.
Property dualism
Property dualism is the view that the world is constituted of one kind of substance – the physical kind – and there exist two distinct kinds of properties: physical properties and mental properties.
It is the view that non-physical, mental properties (such as beliefs,
desires and emotions) inhere in some physical bodies (at least, brains).
Sub-varieties of property dualism include:
Emergent materialism
asserts that when matter is organized in the appropriate way (i.e. in
the way that living human bodies are organized), mental properties
emerge in a way not fully accountable for by physical laws.
These emergent properties have an independent ontological status and
cannot be reduced to, or explained in terms of, the physical substrate
from which they emerge. They are dependent on the physical properties
from which they emerge, but opinions vary as to the coherence of top–down causation, i.e. the causal effectiveness of such properties. A form of emergent materialism has been espoused by David Chalmers and the concept has undergone something of a renaissance in recent years, but it was already suggested in the 19th century by William James.
Epiphenomenalism is a doctrine first formulated by Thomas Henry Huxley.
It consists of the view that mental phenomena are causally ineffectual,
where one or more mental states do not have any influence on physical
states or mental phenomena are the effects, but not the causes, of
physical phenomena. Physical events can cause other physical and mental
events, but mental events cannot cause anything since they are just
causally inert by-products (i.e. epiphenomena) of the physical world. This view has been defended by Frank Jackson.
Non-reductive physicalism
is the view that mental properties form a separate ontological class to
physical properties: mental states (such as qualia) are not reducible
to physical states. The ontological stance towards qualia in the case of
non-reductive physicalism does not imply that qualia are causally
inert; this is what distinguishes it from epiphenomenalism.
Panpsychism
is the view that all matter has a mental aspect, or, alternatively, all
objects have a unified center of experience or point of view.
Superficially, it seems to be a form of property dualism, since it
regards everything as having both mental and physical properties.
However, some panpsychists say that mechanical behaviour is derived from
the primitive mentality of atoms and molecules—as are sophisticated
mentality and organic behaviour, the difference being attributed to the
presence or absence of complex structure in a compound object. So long as the reduction of non-mental properties to mental ones is in place, panpsychism is not a (strong) form of property dualism; otherwise it is.
Dual aspect theory
Dual aspect theory or dual-aspect monism is the view that the mental and the physical
are two aspects of, or perspectives on, the same substance. (Thus it is
a mixed position, which is monistic in some respects). In modern
philosophical writings, the theory's relationship to neutral monism
has become somewhat ill-defined, but one proffered distinction says
that whereas neutral monism allows the context of a given group of
neutral elements and the relationships into which they enter to
determine whether the group can be thought of as mental, physical, both,
or neither, dual-aspect theory suggests that the mental and the
physical are manifestations (or aspects) of some underlying substance,
entity or process that is itself neither mental nor physical as normally
understood. Various formulations of dual-aspect monism also require the
mental and the physical to be complementary, mutually irreducible and
perhaps inseparable (though distinct).
Experiential dualism
This
is a philosophy of mind that regards the degrees of freedom between
mental and physical well-being as not synonymous thus implying an
experiential dualism between body and mind. An example of these
disparate degrees of freedom is given by Allan Wallace
who notes that it is "experientially apparent that one may be
physically uncomfortable—for instance, while engaging in a strenuous
physical workout—while mentally cheerful; conversely, one may be
mentally distraught while experiencing physical comfort".
Experiential dualism notes that our subjective experience of merely
seeing something in the physical world seems qualitatively different
than mental processes like grief that comes from losing a loved one.
This philosophy is a proponent of causal dualism, which is defined as
the dual ability for mental states and physical states to affect one
another. Mental states can cause changes in physical states and vice
versa.
However, unlike cartesian dualism or some other systems,
experiential dualism does not posit two fundamental substances in
reality: mind and matter. Rather, experiential dualism is to be
understood as a conceptual framework that gives credence to the
qualitative difference between the experience of mental and physical
states. Experiential dualism is accepted as the conceptual framework of
Madhyamaka Buddhism.
Madhayamaka Buddhism goes further, finding fault with the monist view of
physicalist philosophies of mind as well in that these generally posit
matter and energy as the fundamental substance of reality. Nonetheless,
this does not imply that the cartesian dualist view is correct, rather
Madhyamaka regards as error any affirming view of a fundamental
substance to reality.
In denying the independent
self-existence of all the phenomena that make up the world of our
experience, the Madhyamaka view departs from both the substance dualism
of Descartes and the substance monism—namely, physicalism—that is
characteristic of modern science. The physicalism propounded by many
contemporary scientists seems to assert that the real world is composed
of physical things-in-themselves, while all mental phenomena are
regarded as mere appearances, devoid of any reality in and of
themselves. Much is made of this difference between appearances and
reality.
Indeed, physicalism, or the idea that matter is the only fundamental substance of reality, is explicitly rejected by Buddhism.
In
the Madhyamaka view, mental events are no more or less real than
physical events. In terms of our common-sense experience, differences of
kind do exist between physical and mental phenomena. While the former
commonly have mass, location, velocity, shape, size, and numerous other
physical attributes, these are not generally characteristic of mental
phenomena. For example, we do not commonly conceive of the feeling of
affection for another person as having mass or location. These physical
attributes are no more appropriate to other mental events such as
sadness, a recalled image from one's childhood, the visual perception of
a rose, or consciousness of any sort. Mental phenomena are, therefore,
not regarded as being physical, for the simple reason that they lack
many of the attributes that are uniquely characteristic of physical
phenomena. Thus, Buddhism has never adopted the physicalist principle
that regards only physical things as real.
Monist solutions to the mind–body problem
In contrast to dualism, monism
does not accept any fundamental divisions. The fundamentally disparate
nature of reality has been central to forms of eastern philosophies for
over two millennia. In Indian and Chinese philosophy, monism is integral to how experience is understood. Today, the most common forms of monism in Western philosophy are physicalist.
Physicalistic monism asserts that the only existing substance is
physical, in some sense of that term to be clarified by our best
science. However, a variety of formulations (see below) are possible. Another form of monism, idealism, states that the only existing substance is mental. Although pure idealism, such as that of George Berkeley, is uncommon in contemporary Western philosophy, a more sophisticated variant called panpsychism,
according to which mental experience and properties may be at the
foundation of physical experience and properties, has been espoused by
some philosophers such as Alfred North Whitehead and David Ray Griffin.
Phenomenalism is the theory that representations (or sense data) of external objects are all that exist. Such a view was briefly adopted by Bertrand Russell and many of the logical positivists during the early 20th century.
A third possibility is to accept the existence of a basic substance
that is neither physical nor mental. The mental and physical would then
both be properties of this neutral substance. Such a position was
adopted by Baruch Spinoza and was popularized by Ernst Mach in the 19th century. This neutral monism, as it is called, resembles property dualism.
Physicalistic monisms
Behaviorism
Behaviorism dominated philosophy of mind for much of the 20th century, especially the first half. In psychology, behaviorism developed as a reaction to the inadequacies of introspectionism.
Introspective reports on one's own interior mental life are not subject
to careful examination for accuracy and cannot be used to form
predictive generalizations. Without generalizability and the possibility
of third-person examination, the behaviorists argued, psychology cannot
be scientific.
The way out, therefore, was to eliminate the idea of an interior mental
life (and hence an ontologically independent mind) altogether and focus
instead on the description of observable behavior.
Parallel to these developments in psychology, a philosophical behaviorism (sometimes called logical behaviorism) was developed. This is characterized by a strong verificationism,
which generally considers unverifiable statements about interior mental
life pointless. For the behaviorist, mental states are not interior
states on which one can make introspective reports. They are just
descriptions of behavior or dispositions to behave in certain ways, made by third parties to explain and predict another's behavior.
Philosophical behaviorism has fallen out of favor since the latter half of the 20th century, coinciding with the rise of cognitivism.
Identity theory
Type physicalism (or type-identity theory) was developed by John Smart and Ullin Place
as a direct reaction to the failure of behaviorism. These philosophers
reasoned that, if mental states are something material, but not
behavioral, then mental states are probably identical to internal states
of the brain. In very simplified terms: a mental state M is nothing other than brain state B.
The mental state "desire for a cup of coffee" would thus be nothing
more than the "firing of certain neurons in certain brain regions".
The
classic Identity theory and Anomalous Monism in contrast. For the
Identity theory, every token instantiation of a single mental type
corresponds (as indicated by the arrows) to a physical token of a single
physical type. For anomalous monism, the token–token correspondences
can fall outside of the type–type correspondences. The result is token
identity.
On the other hand, even granted the above, it does not follow that
identity theories of all types must be abandoned. According to token
identity theories, the fact that a certain brain state is connected with
only one mental state of a person does not have to mean that there is
an absolute correlation between types of mental state and types of brain
state. The type–token distinction can be illustrated by a simple
example: the word "green" contains four types of letters (g, r, e, n)
with two tokens (occurrences) of the letter e along with one each
of the others.
The idea of token identity is that only particular occurrences of mental
events are identical with particular occurrences or tokenings of
physical events. Anomalous monism (see below) and most other non-reductive physicalisms are token-identity theories. Despite these problems, there is a renewed interest in the type identity theory today, primarily due to the influence of Jaegwon Kim.
Mental states are characterized by their causal relations with
other mental states and with sensory inputs and behavioral outputs.
Functionalism abstracts away from the details of the physical
implementation of a mental state by characterizing it in terms of
non-mental functional properties. For example, a kidney is characterized
scientifically by its functional role in filtering blood and
maintaining certain chemical balances.
Non-reductive physicalism
Non-reductionist philosophers hold firmly to two essential
convictions with regard to mind–body relations: 1) Physicalism is true
and mental states must be physical states, but 2) All reductionist
proposals are unsatisfactory: mental states cannot be reduced to
behavior, brain states or functional states. Hence, the question arises whether there can still be a non-reductive physicalism. Donald Davidson's anomalous monism
is an attempt to formulate such a physicalism. He "thinks that when one
runs across what are traditionally seen as absurdities of Reason, such
as akrasia or self-deception, the personal psychology framework is not
to be given up in favor of the subpersonal one, but rather must be
enlarged or extended so that the rationality set out by the principle of
charity can be found elsewhere."
Davidson uses the thesis of supervenience:
mental states supervene on physical states, but are not reducible to
them. "Supervenience" therefore describes a functional dependence: there
can be no change in the mental without some change in the
physical–causal reducibility between the mental and physical without
ontological reducibility.
Non-reductive physicalism, however, is irreconcilable with
self-identity over time. The brain goes on from one moment of time to
another; the brain thus has identity through time. But its states of
awareness do not go on from one moment to the next. There is no enduring
self – no “I” (capital-I) that goes on from one moment to the next. An
analogy of the self or the “I” would be the flame of a candle. The
candle and the wick go on from one moment to the next, but the flame
does not go on. There is a different flame at each moment of the
candle’s burning. The flame displays a type of continuity in that the
candle does not go out while it is burning, but there is not really any
identity of the flame from one moment to another over time. The scenario
is similar on non-reductive physicalism with states of awareness. Every
state of the brain at different times has a different state of
awareness related to it, but there is no enduring self or “I” from one
moment to the next. Similarly, it is an illusion that one is the same
individual who walked into class this morning. In fact, one is not the
same individual because there is no personal identity over time. If one
does exist and one is the same individual who entered into class this
morning, then a non-reductive physicalist view of the self should be
dismissed.
Because non-reductive physicalist theories attempt to both retain
the ontological distinction between mind and body and try to solve the
"surfeit of explanations puzzle" in some way; critics often see this as a
paradox and point out the similarities to epiphenomenalism, in that it is the brain that is seen as the root "cause" not the mind, and the mind seems to be rendered inert.
Epiphenomenalism regards one or more mental states as the
byproduct of physical brain states, having no influence on physical
states. The interaction is one-way (solving the "surfeit of explanations
puzzle") but leaving us with non-reducible mental states (as a
byproduct of brain states) – causally reducible, but ontologically
irreducible to physical states. Pain would be seen by epiphenomenalists
as being caused by the brain state but as not having effects on other
brain states, though it might have effects on other mental states (i.e.
cause distress).
Weak emergentism
Weak emergentism is a form of "non-reductive physicalism" that
involves a layered view of nature, with the layers arranged in terms of
increasing complexity and each corresponding to its own special science.
Some philosophers
hold that emergent properties causally interact with more fundamental
levels, while others maintain that higher-order properties simply
supervene over lower levels without direct causal interaction. The
latter group therefore holds a less strict, or "weaker", definition of
emergentism, which can be rigorously stated as follows: a property P of
composite object O is emergent if it is metaphysically impossible for
another object to lack property P if that object is composed of parts
with intrinsic properties identical to those in O and has those parts in
an identical configuration.
Sometimes emergentists use the example of water having a new property when Hydrogen H and Oxygen O combine to form H2O
(water). In this example there "emerges" a new property of a
transparent liquid that would not have been predicted by understanding
hydrogen and oxygen as gases. This is analogous to physical properties
of the brain giving rise to a mental state. Emergentists try to solve
the notorious mind–body gap this way. One problem for emergentism is the
idea of "causal closure" in the world that does not allow for a
mind-to-body causation.
Eliminative materialism
If one is a materialist and believes that all aspects of our common-sense psychology will find reduction to a mature cognitive neuroscience, and that non-reductive materialism is mistaken, then one can adopt a final, more radical position: eliminative materialism.
There are several varieties of eliminative materialism, but all maintain that our common-sense "folk psychology" badly misrepresents the nature of some aspect of cognition. Eliminativists such as Patricia and Paul Churchland
argue that while folk psychology treats cognition as fundamentally
sentence-like, the non-linguistic vector/matrix model of neural network
theory or connectionism will prove to be a much more accurate account of how the brain works.
The Churchlands often invoke the fate of other, erroneous popular theories and ontologies that have arisen in the course of history.
For example, Ptolemaic astronomy served to explain and roughly predict
the motions of the planets for centuries, but eventually this model of
the solar system was eliminated in favor of the Copernican model. The
Churchlands believe the same eliminative fate awaits the
"sentence-cruncher" model of the mind in which thought and behavior are
the result of manipulating sentence-like states called "propositional attitudes".
Mysterianism
Some philosophers take an epistemic approach and argue that the
mind–body problem is currently unsolvable, and perhaps will always
remain unsolvable to human beings. This is usually termed New mysterianism. Colin McGinn holds that human beings are cognitively closed
in regards to their own minds. According to McGinn human minds lack the
concept-forming procedures to fully grasp how mental properties such as
consciousness arise from their causal basis. An example would be how an elephant is cognitively closed in regards to particle physics.
A more moderate conception has been expounded by Thomas Nagel,
which holds that the mind–body problem is currently unsolvable at the
present stage of scientific development and that it might take a future
scientific paradigm shift or revolution to bridge the explanatory gap. Nagel posits that in the future a sort of "objective phenomenology" might be able to bridge the gap between subjective conscious experience and its physical basis.
Linguistic criticism of the mind–body problem
Each
attempt to answer the mind–body problem encounters substantial
problems. Some philosophers argue that this is because there is an
underlying conceptual confusion. These philosophers, such as Ludwig Wittgenstein and his followers in the tradition of linguistic criticism, therefore reject the problem as illusory.
They argue that it is an error to ask how mental and biological states
fit together. Rather it should simply be accepted that human experience
can be described in different ways—for instance, in a mental and in a
biological vocabulary. Illusory problems arise if one tries to describe
the one in terms of the other's vocabulary or if the mental vocabulary
is used in the wrong contexts.
This is the case, for instance, if one searches for mental states of
the brain. The brain is simply the wrong context for the use of mental
vocabulary—the search for mental states of the brain is therefore a category error or a sort of fallacy of reasoning.
Today, such a position is often adopted by interpreters of Wittgenstein such as Peter Hacker. However, Hilary Putnam,
the originator of functionalism, has also adopted the position that the
mind–body problem is an illusory problem which should be dissolved
according to the manner of Wittgenstein.
Naturalism and its problems
The
thesis of physicalism is that the mind is part of the material (or
physical) world. Such a position faces the problem that the mind has
certain properties that no other material thing seems to possess.
Physicalism must therefore explain how it is possible that these
properties can nonetheless emerge from a material thing. The project of
providing such an explanation is often referred to as the "naturalization of the mental".
Some of the crucial problems that this project attempts to resolve
include the existence of qualia and the nature of intentionality.
Qualia
Many mental states seem to be experienced subjectively in different ways by different individuals. And it is characteristic of a mental state that it has some experiential quality,
e.g. of pain, that it hurts. However, the sensation of pain between two
individuals may not be identical, since no one has a perfect way to
measure how much something hurts or of describing exactly how it feels
to hurt. Philosophers and scientists therefore ask where these
experiences come from. The existence of cerebral events, in and of
themselves, cannot explain why they are accompanied by these
corresponding qualitative experiences. The puzzle of why many cerebral
processes occur with an accompanying experiential aspect in
consciousness seems impossible to explain.
Yet it also seems to many that science will eventually have to explain such experiences. This follows from an assumption about the possibility of reductive explanations.
According to this view, if an attempt can be successfully made to
explain a phenomenon reductively (e.g., water), then it can be explained
why the phenomenon has all of its properties (e.g., fluidity,
transparency).
In the case of mental states, this means that there needs to be an
explanation of why they have the property of being experienced in a
certain way.
The 20th-century German philosopher Martin Heidegger criticized the ontological
assumptions underpinning such a reductive model, and claimed that it
was impossible to make sense of experience in these terms. This is
because, according to Heidegger, the nature of our subjective experience
and its qualities is impossible to understand in terms of Cartesian
"substances" that bear "properties". Another way to put this is that
the very concept of qualitative experience is incoherent in terms of—or
is semantically incommensurable with the concept of—substances that bear properties.
This problem of explaining introspective first-person aspects of
mental states and consciousness in general in terms of third-person
quantitative neuroscience is called the explanatory gap. There are several different views of the nature of this gap among contemporary philosophers of mind. David Chalmers and the early Frank Jackson interpret the gap as ontological in nature; that is, they maintain that qualia can never be explained by science because physicalism is false. There are two separate categories involved and one cannot be reduced to the other. An alternative view is taken by philosophers such as Thomas Nagel and Colin McGinn. According to them, the gap is epistemological
in nature. For Nagel, science is not yet able to explain subjective
experience because it has not yet arrived at the level or kind of
knowledge that is required. We are not even able to formulate the
problem coherently.
For McGinn, on other hand, the problem is one of permanent and inherent
biological limitations. We are not able to resolve the explanatory gap
because the realm of subjective experiences is cognitively closed to us
in the same manner that quantum physics is cognitively closed to
elephants. Other philosophers liquidate the gap as purely a semantic problem. This semantic problem, of course, led to the famous "Qualia Question", which is: Does Red cause Redness?
Intentionality is the capacity of mental states to be directed towards (about) or be in relation with something in the external world. This property of mental states entails that they have contents and semantic referents and can therefore be assigned truth values.
When one tries to reduce these states to natural processes there arises
a problem: natural processes are not true or false, they simply happen.
It would not make any sense to say that a natural process is true or
false. But mental ideas or judgments are true or false, so how then can
mental states (ideas or judgments) be natural processes? The possibility
of assigning semantic value to ideas must mean that such ideas are
about facts. Thus, for example, the idea that Herodotus
was a historian refers to Herodotus and to the fact that he was a
historian. If the fact is true, then the idea is true; otherwise, it is
false. But where does this relation come from? In the brain, there are
only electrochemical processes and these seem not to have anything to do
with Herodotus.
Humans
are corporeal beings and, as such, they are subject to examination and
description by the natural sciences. Since mental processes are
intimately related to bodily processes, the descriptions that the
natural sciences furnish of human beings play an important role in the
philosophy of mind. There are many scientific disciplines that study processes related to the mental. The list of such sciences includes: biology, computer science, cognitive science, cybernetics, linguistics, medicine, pharmacology, and psychology.
Neurobiology
The theoretical background of biology, as is the case with modern natural sciences
in general, is fundamentally materialistic. The objects of study are,
in the first place, physical processes, which are considered to be the
foundations of mental activity and behavior.
The increasing success of biology in the explanation of mental
phenomena can be seen by the absence of any empirical refutation of its
fundamental presupposition: "there can be no change in the mental states
of a person without a change in brain states."
Within the field of neurobiology, there are many subdisciplines
that are concerned with the relations between mental and physical states
and processes: Sensory neurophysiology investigates the relation between the processes of perception and stimulation. Cognitive neuroscience studies the correlations between mental processes and neural processes. Neuropsychology describes the dependence of mental faculties on specific anatomical regions of the brain. Lastly, evolutionary biology
studies the origins and development of the human nervous system and, in
as much as this is the basis of the mind, also describes the ontogenetic and phylogenetic development of mental phenomena beginning from their most primitive stages. Evolutionary biology furthermore places tight constraints on any philosophical theory of the mind, as the gene-based mechanism of natural selection
does not allow any giant leaps in the development of neural complexity
or neural software but only incremental steps over long time periods.
Since the 1980s, sophisticated neuroimaging procedures, such as fMRI
(above), have furnished increasing knowledge about the workings of the
human brain, shedding light on ancient philosophical problems.
The methodological
breakthroughs of the neurosciences, in particular the introduction of
high-tech neuroimaging procedures, has propelled scientists toward the
elaboration of increasingly ambitious research programs: one of the main
goals is to describe and comprehend the neural processes which
correspond to mental functions (see: neural correlate). Several groups are inspired by these advances.
Computer science
Computer science concerns itself with the automatic processing of information (or at least with physical systems of symbols to which information is assigned) by means of such things as computers. From the beginning, computer programmers
have been able to develop programs that permit computers to carry out
tasks for which organic beings need a mind. A simple example is
multiplication. It is not clear whether computers could be said to have a
mind. Could they, someday, come to have what we call a mind? This
question has been propelled into the forefront of much philosophical
debate because of investigations in the field of artificial intelligence (AI).
Within AI, it is common to distinguish between a modest research
program and a more ambitious one: this distinction was coined by John Searle in terms of a weak AI and strong AI.
The exclusive objective of "weak AI", according to Searle, is the
successful simulation of mental states, with no attempt to make
computers become conscious or aware, etc. The objective of strong AI, on
the contrary, is a computer with consciousness similar to that of human
beings. The program of strong AI goes back to one of the pioneers of computation Alan Turing. As an answer to the question "Can computers think?", he formulated the famous Turing test.
Turing believed that a computer could be said to "think" when, if
placed in a room by itself next to another room that contained a human
being and with the same questions being asked of both the computer and
the human being by a third party human being, the computer's responses
turned out to be indistinguishable from those of the human. Essentially,
Turing's view of machine intelligence followed the behaviourist model
of the mind—intelligence is as intelligence does. The Turing test has
received many criticisms, among which the most famous is probably the Chinese roomthought experiment formulated by Searle.
The question about the possible sensitivity (qualia)
of computers or robots still remains open. Some computer scientists
believe that the specialty of AI can still make new contributions to the
resolution of the "mind–body problem". They suggest that based on the
reciprocal influences between software and hardware that takes place in
all computers, it is possible that someday theories can be discovered
that help us to understand the reciprocal influences between the human
mind and the brain (wetware).
Psychology
Psychology is the science that investigates mental states directly.
It uses generally empirical methods to investigate concrete mental
states like joy, fear or obsessions. Psychology investigates the laws that bind these mental states to each other or with inputs and outputs to the human organism.
An example of this is the psychology of perception. Scientists working in this field have discovered general principles of the perception of forms. A law of the psychology of forms says that objects that move in the same direction are perceived as related to each other.
This law describes a relation between visual input and mental
perceptual states. However, it does not suggest anything about the
nature of perceptual states. The laws discovered by psychology are
compatible with all the answers to the mind–body problem already
described.
Cognitive science
Cognitive science is the interdisciplinary scientific study of the mind and its processes. It examines what cognition
is, what it does, and how it works. It includes research on
intelligence and behavior, especially focusing on how information is
represented, processed, and transformed (in faculties such as
perception, language, memory, reasoning, and emotion) within nervous
systems (human or other animal) and machines (e.g. computers). Cognitive
science consists of multiple research disciplines, including psychology, artificial intelligence, philosophy, neuroscience, linguistics, anthropology, sociology, and education.
It spans many levels of analysis, from low-level learning and decision
mechanisms to high-level logic and planning; from neural circuitry to
modular brain organisation. Rowlands
argues that cognition is enactive, embodied, embedded, affective and
(potentially) extended. The position is taken that the "classical
sandwich" of cognition sandwiched between perception and action is
artificial; cognition has to be seen as a product of a strongly coupled
interaction that cannot be divided this way.
Near-death research
In the field of near-death research, the following phenomenon, among
others, occurs: For example, during some brain operations the brain is
artificially and measurably deactivated. Nevertheless, some patients
report during this phase that they have perceived what is happening in
their surroundings, i.e. that they have had consciousness. Patients also
report experiences during a cardiac arrest. There is the following
problem: As soon as the brain is no longer supplied with blood and thus
with oxygen after a cardiac arrest, the brain ceases its normal
operation after about 15 seconds, i.e. the brain falls into a state of
unconsciousness.
Philosophy of mind in the continental tradition
Most
of the discussion in this article has focused on one style or tradition
of philosophy in modern Western culture, usually called analytic philosophy (sometimes described as Anglo-American philosophy). Many other schools of thought exist, however, which are sometimes subsumed under the broad (and vague) label of continental philosophy.
In any case, though topics and methods here are numerous, in relation
to the philosophy of mind the various schools that fall under this label
(phenomenology, existentialism,
etc.) can globally be seen to differ from the analytic school in that
they focus less on language and logical analysis alone but also take in
other forms of understanding human existence and experience. With
reference specifically to the discussion of the mind, this tends to
translate into attempts to grasp the concepts of thought and perceptual experience in some sense that does not merely involve the analysis of linguistic forms.
Immanuel Kant's Critique of Pure Reason,
first published in 1781 and presented again with major revisions in
1787, represents a significant intervention into what will later become
known as the philosophy of mind. Kant's first critique is generally recognized as among the most significant works of modern philosophy in the West. Kant is a figure whose influence is marked in both continental and analytic/Anglo-American philosophy. Kant's work develops an in-depth study of transcendental consciousness, or the life of the mind as conceived through the universal categories of understanding.
In Georg Wilhelm Friedrich Hegel's Philosophy of Mind (frequently translated as Philosophy of Spirit or Geist), the third part of his Encyclopedia of the Philosophical Sciences,
Hegel discusses three distinct types of mind: the "subjective
mind/spirit", the mind of an individual; the "objective mind/spirit",
the mind of society and of the State; and the "Absolute mind/spirit",
the position of religion, art, and philosophy. See also Hegel's The Phenomenology of Spirit. Nonetheless, Hegel's work differs radically from the style of Anglo-American philosophy of mind.
In 1896, Henri Bergson made in Matter and Memory
"Essay on the relation of body and spirit" a forceful case for the
ontological difference of body and mind by reducing the problem to the
more definite one of memory, thus allowing for a solution built on the empirical test case of aphasia.
In modern times, the two main schools that have developed in
response or opposition to this Hegelian tradition are phenomenology and
existentialism. Phenomenology, founded by Edmund Husserl, focuses on the contents of the human mind (see noema) and how processes shape our experiences.
There
are countless subjects that are affected by the ideas developed in the
philosophy of mind. Clear examples of this are the nature of death and its definitive character, the nature of emotion, of perception and of memory. Questions about what a person is and what his or her identity
have to do with the philosophy of mind. There are two subjects that, in
connection with the philosophy of the mind, have aroused special
attention: free will and the self.
In the context of philosophy of mind, the problem of free will takes on renewed intensity. This is the case for materialistic determinists.
According to this position, natural laws completely determine the
course of the material world. Mental states, and therefore the will as
well, would be material states, which means human behavior and decisions
would be completely determined by natural laws. Some take this
reasoning a step further: people cannot determine by themselves what
they want and what they do. Consequently, they are not free.
This argumentation is rejected, on the one hand, by the compatibilists.
Those who adopt this position suggest that the question "Are we free?"
can only be answered once we have determined what the term "free" means.
The opposite of "free" is not "caused" but "compelled" or "coerced". It
is not appropriate to identify freedom with indetermination. A free act
is one where the agent could have done otherwise if it had chosen
otherwise. In this sense a person can be free even though determinism is
true. The most important compatibilist in the history of the philosophy was David Hume. More recently, this position is defended, for example, by Daniel Dennett.
On the other hand, there are also many incompatibilists who reject the argument because they believe that the will is free in a stronger sense called libertarianism.
These philosophers affirm the course of the world is either a) not
completely determined by natural law where natural law is intercepted by
physically independent agency,
b) determined by indeterministic natural law only, or c) determined by
indeterministic natural law in line with the subjective effort of
physically non-reducible agency.
Under Libertarianism, the will does not have to be deterministic and,
therefore, it is potentially free. Critics of the second proposition (b)
accuse the incompatibilists of using an incoherent concept of freedom.
They argue as follows: if our will is not determined by anything, then
we desire what we desire by pure chance. And if what we desire is purely
accidental, we are not free. So if our will is not determined by
anything, we are not free.
Self
The philosophy of mind also has important consequences for the
concept of "self". If by "self" or "I" one refers to an essential,
immutable nucleus of the person, some modern philosophers of mind, such as Daniel Dennett believe that no such thing exists. According to Dennett and other contemporaries, the self is considered an illusion. The idea of a self as an immutable essential nucleus derives from the idea of an immaterial soul.
Such an idea is unacceptable to modern philosophers with physicalist
orientations and their general skepticism of the concept of "self" as
postulated by David Hume, who could never catch himself not doing, thinking or feeling anything. However, in the light of empirical results from developmental psychology, developmental biology and neuroscience,
the idea of an essential inconstant, material nucleus—an integrated
representational system distributed over changing patterns of synaptic
connections—seems reasonable.
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