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Dualism (philosophy of mind)

2007 Schools Wikipedia Selection. Related subjects: Philosophy

   René Descartes' illustration of dualism. Inputs are passed on by the
   sensory organs to the epiphysis in the brain and from there to the
   immaterial spirit.
   Enlarge
   René Descartes' illustration of dualism. Inputs are passed on by the
   sensory organs to the epiphysis in the brain and from there to the
   immaterial spirit.

   In philosophy of mind, dualism is a set of views about the relationship
   between mind and matter, which begins with the claim that mental
   phenomena are, in some respects, non- physical.

   The first manifestations of mind/body dualism probably go back to the
   origins of conscious thought, when people began to speculate about the
   existence of an incorporeal soul which bore the faculties of
   intelligence and wisdom. We first encounter similar ideas in Western
   philosophy with the writings of Plato and Aristotle, who maintained,
   for different reasons, that man's "intelligence" (a faculty of the mind
   or soul) could not be identified with, or explained in terms of, their
   physical body.

   The best-known version of dualism is due to René Descartes (1641), and
   holds that the mind is a nonphysical substance. 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.
   Hence, he was the first to formulate the mind/body problem in the form
   in which it exists today. Dualism is contrasted with various kinds of
   monism, including physicalism and phenomenalism. Substance dualism is
   contrasted with all forms of materialism, but property dualism may be
   considered a form of emergent materialism and thus would only be
   contrasted with non-emergent materialism. This article discusses the
   various forms of dualism and the arguments which have been made both
   for and against this thesis.

Historical overview

Plato and Aristotle

   In the dialogue Phaedo, Plato formulated his famous doctrine of eternal
   Forms as distinct and immaterial substances of which the objects and
   other phenomena that we perceive in the world are nothing more than
   mere shadows. Plato's doctrine was the prototype of all future
   manifestations of substance dualism in ontology. But Plato's doctrine
   of the Forms is not to be considered some sort of ancient and
   superseded metaphysical notion because it has precise implications for
   the philosophy of mind and the mind-body problem in particular.

   Plato makes it clear, in the Phaedo, that the Forms are the universalia
   ante rem, i.e. they are universal concepts (or ideas) which make all of
   the phenomenal world intelligible. Consequently, in order for the
   intellect (the most important aspect of the mind in philosophy up until
   Descartes) to have access to any kind of knowledge with regard to any
   aspect of the universe, it must necessarily be a non-physical,
   immaterial entity (or property of some such entity) itself. So, it is
   clear on the basis of the texts that Plato was a very powerful
   precursor of Descartes and his subsequent more stringent formulation of
   the doctrine of substance dualism.

   Aristotle strongly rejected Plato's notion of Forms as independently
   existing entities. In the Metaphysics, he already points to the central
   problems with this idea. On the one hand, if we say that the
   particulars of the phenomenal world participate or share in the Form,
   we seem to be destroying the Form's essential and indispensable unity.
   On the other, if we say that the particulars merely resemble, or are
   copies of, the Form, we seem to need an extra form to explain the
   connection between the members of the class consisting of
   the-particulars-and-the-form, and so on, leading to an infinite
   regress. This argument, originally formulated by Plato himself in the
   Parmenides, was later given the name of the " third man argument" by
   Aristotle.

   For these reasons, Aristotle revised the theory of forms so as to
   eliminate the idea of their independent existence from concrete,
   particular entities. The form of something, for Aristotle, is the
   nature or essence (ousia, in Greek) of that thing. To say that Socrates
   and Callias are both men is not to say that there is some transcendent
   entity "man" to which both Socrates and Callias belong. The form is
   indeed substance but it is not substance over and above the substance
   of the concrete entities which it characterizes. Aristotle rejects both
   universalia in rebus as well as universalia ante rem. Some philosophers
   and thinkers have taken this to be a form of materialism and there may
   be something to their arguments. However, what is important from the
   perspective of philosophy of mind is that Aristotle does not believe
   that intellect can be conceived of as something material. He argues as
   follows: if the intellect were material then it could not receive all
   of the forms. If the intellect were a specific material organ (or part
   of one) then it would be restricted to receiving only certain kinds of
   information, as the eye is restricted to receiving visual data and the
   ear is restricted to receiving auditory data. Since the intellect is
   capable of receiving and reflecting on all forms of data, then it must
   not be a physical organ and, hence, it must be immaterial.

From Neoplatonism to Scholasticism

   Early Christianity seems to have struggled to come to terms with the
   identification of a unique position with regard to the question of the
   relationship between mind and body, just as it struggled to define the
   relationship of the ontological status of Christ himself (see
   homoousianism, homoiousianism, Arianism, etc). In the early Middle
   Ages, a consensus seemed to emerge around what is now called
   Neoplatonism. The doctrines of Neoplatonism were essentially minor
   modifications on Plato's general ideas about the immortality of the
   soul and the nature of the Forms. The Neoplatonic Christians identified
   the Forms with souls and believed that the soul was the substance of
   each individual human being, while the body was just a shadow or copy
   of these eternal phenomena.

   Later philosophers, following in the neo-Aristotelian trail blazed by
   Thomas Aquinas, came to develop a trinitarian notion of forms which
   paralleled the Trinitarian doctrine of Father, Son and Holy Spirit:
   forms, intellect and soul were three aspects or parts of the same
   singular phenomenon. For Aquinas, the soul (or intellect) remained the
   substance of the human being, but, somewhat similarly to Aristotle's
   proposal, it was only through its manifestation inside the human body
   that a person could be said to be a person. While the soul (intellect
   or form) could exist independently of the body (unlike in Aristotle)
   the soul by itself did not constitute a person. Hence, Aquinas
   suggested that instead of saying "St. Peter pray for us" one should
   rather say something like "soul of St. Peter pray for us", since all
   that remained of St. Peter, after his death, was his soul. All things
   connected with the body, such as personal memories, were cancelled out
   with the end of one's corporeal existence.

   There are different views on this question in modern Christianity.
   Official Catholic Church doctrine, as illustrated by the Apostle's
   Creed, claims that at the Second Coming of Christ, the body is reunited
   with the soul at the resurrection, and the whole person (i.e. body and
   soul) then goes to Heaven or Hell. Hence, there is a sort of
   inseparability of soul, mind and body which is even more strongly
   reminiscent of Aristotle than the positions expressed by Thomas
   Aquinas.

   Some revisionist Protestant theologians do not accept this doctrine and
   insist, instead, that only the immaterial soul (and hence mind or
   intellect) goes to Heaven, leaving the body (and brain) behind it
   forever.

   Still other Christians, including Seventh-Day Adventists, teach that
   the soul, if it exists at all, does not survive death, citing biblical
   claims that the dead know nothing, and that a person's thoughts perish
   with them when they die. According to this view, death is like a sleep
   - consciousness is lost at death, but is restored to the resurrected
   body at the resurrection. The concept of a soul as distinct from the
   body would therefore be redundant.

Descartes and his disciples

   A schematic overview of occasionalism, a theory of causation that
   emerged as a solution to the problem of interactionism arising out of
   Descartes' dualism.
   Enlarge
   A schematic overview of occasionalism, a theory of causation that
   emerged as a solution to the problem of interactionism arising out of
   Descartes' dualism.

   In his Meditations on First Philosophy, Descartes embarked upon a quest
   in which he called all his previous beliefs into doubt, in order to
   find out what he could be certain of.In doing so, he discovered that he
   could doubt whether he had a body (it could be that he was dreaming of
   it or that it was an illusion created by an evil demon), but he
   couldn't doubt whether he had a mind. This gave Descartes his first
   inkling that the mind and body were different things. The mind,
   according to Descartes, was a "thinking thing" (lat. res cogitans), and
   an immaterial substance. This "thing" was the essence of himself, that
   which doubts, believes, hopes, and thinks. The distinction between mind
   and body is argued in Meditation VI as follows: I have a clear and
   distinct idea of myself as a thinking non-extended thing, and a clear
   and distinct idea of body as an extended and non-thinking thing.
   Whatever I can conceive clearly and distinctly, God can so create. So,
   Descartes argues, the mind, a thinking thing, can exist apart from its
   extended body. And therefore, the mind is a substance distinct from the
   body, a substance whose essence is thought.

   The central claim of what is often called Cartesian dualism, in honour
   of Descartes, is that the immaterial mind and the material body, while
   being [ontology|ontologically] distinct subtances, causally interact.
   This is an idea which continues to feature prominently in many
   non-European philosophies. Mental events cause physical events, and
   vice-versa. But this leads to a substantial problem for Cartesian
   dualism: How can an immaterial mind cause anything in a material body,
   and vice-versa? This has often been called the "problem of
   interactionism".

   Descartes himself struggled to come up with a feasible answer to this
   problem. In his letter to Elisabeth of Bohemia, Princess Palatine, he
   suggested that animal spirits interacted with the body through the
   pineal gland, a small gland in the centre of the brain, between the two
   hemispheres. The term "Cartesian dualism" is also often associated with
   this more specific notion of causal interaction through the pineal
   gland. However, this explanation was not satisfactory: how can an
   immaterial mind interact with the physical pineal gland? Because
   Descartes' was such a difficult theory to defend, some of his
   disciples, such as Arnold Geulincx and Nicholas Malebranche, proposed a
   different explanation: That all mind-body interactions required the
   direct intervention of God. According to these philosophers, the
   appropriate states of mind and body were only the occasions for such
   intervention, not real causes. These occasionalists maintained the
   strong thesis that all causation was directly dependent on God, instead
   of holding that all causation was natural except for that between mind
   and body.

Types of ontological dualism

   Ontological dualism makes dual commitments about the nature of
   existence as it relates to mind and matter, and can be divided into
   three different types:

          (1) Substance dualism asserts that mind and matter are
          fundamentally distinct kinds of substances.

          (2) property dualism suggests that the ontological distinction
          lies in the differences between properties of mind and matter
          (as in emergentism).

          (3) predicate dualism claims the irreducibility of mental
          predicates to physical predicates.

Substance dualism

   Substance dualism is a type of dualism most famously defended by
   Descartes, which states that there are two fundamental kinds of
   substance: mental and material. The mental does not have extension in
   space, and the material cannot think. Substance dualism is a viewpoint
   which contradicts physicalism, one of the most popular views in modern
   philosophy of mind. However, it may be regarded as important
   historically in that it has given rise to much thought over the famous
   mind-body problem. It may also be noted that philosophical
   interpretations of quantum mechanics -- especially the consciousness
   causes collapse interpretation -- are not a revival of substance
   dualism, since these views generally claim the observer is entangled in
   the object being observed, not a separate substance as in the case of
   substance dualism. Substance dualism is a philosophical position
   compatible with most theologies which claim that immortal souls occupy
   an independent "realm" of existence which is distinct from that of the
   physical world. David Chalmers recently developed a thought experiment
   inspired by the movie The Matrix in which substance dualism could be
   true: Consider a computer simulation in which the bodies of the
   creatures are controlled by their minds and the minds remain strictly
   external to the simulation. The creatures can do all the science they
   want in the world, but they will never be able to figure out where
   their minds are, for they do not exist in their observable universe.
   This is a case of substance dualism with respect to computer
   simulation. This naturally differs from a computer simulation in which
   the minds are part of the simulation. In such a case, substance monism
   would be true.

Property dualism

   Property dualism asserts that when matter is organized in the
   appropriate way (i.e. in the way that living human bodies are
   organized), mental properties emerge. Hence, it is a sub-branch of
   emergent materialism. Different versions of property dualism describe
   this in different ways. Epiphenomenalism asserts that while material
   causes give rise to sensations, volitions, ideas, etc., such mental
   phenomena themselves cause nothing further: they are causal dead-ends.
   Interactionism, on the other hand, allows that mental causes can
   produce material effects, and vice-versa.

Predicate dualism

   Predicate dualism is the view espoused by most non-reductive
   physicalists, such as Donald Davidson and Jerry Fodor, who maintain
   that while there is only one ontological category of substances and
   properties of substances (usually physical), the predicates that we use
   to describe mental events cannot be redescribed in terms of (or reduced
   to) physical predicates of natural languages. If we characterize
   predicate monism as the view subscribed to by eliminative materialists,
   who maintain that such intentional predicates as believe, desire,
   think, feel, etc., will eventually be eliminated from both the language
   of science and from ordinary language because the entities to which
   they refer do not exist, then predicate dualism is most easily defined
   as the negation of this position. Predicate dualists believe that
   so-called "folk psychology", with all of its propositional attitude
   ascriptions, is an ineliminable part of the enterprise of describing,
   explaining and understanding human mental states and behaviour.

   Davidson, for example, subscribes to Anomalous Monism, according to
   which there can be no strict psycho-physical laws which connect mental
   and physical events under their descriptions as mental and physical
   events. However, all mental events also have physical descriptions. It
   is in terms of the latter that such events can be connected in law-like
   relations with other physical events. Mental predicates are irreducibly
   different in character (rational, holistic and necessary) from physical
   predicates (contingent, atomic and causal).

Types of interaction dualism

   Three varieties of dualism. The arrows indicate the direction of the
   causal interactions.
   Enlarge
   Three varieties of dualism. The arrows indicate the direction of the
   causal interactions.

Interactionism

   Interactionism is the view that mental states, such as beliefs and
   desires, causally interact with physical states. This is a position
   which is very appealing to common-sense intuitions, notwithstanding the
   fact that it is very difficult to establish its validity or correctness
   by way of logical argumentation or empirical proof. It is appealing to
   common-sense because we are surrounded by such everyday occurrences as
   a child's touching a hot stove (physical event) which causes him to
   feel pain ( mental event) and then yell and scream (physical event)
   which causes his parents to experience a sensation of fear and
   protectiveness (mental event) and so on.

Epiphenomalism

   According to epiphenomenalism, all mental events are caused by a
   physical event and have no physical consequences. So, a mental event of
   deciding to pick up a rock (call it "M") is caused by the firing of
   specific neurons in the brain (call it "P"), however when the arm and
   hand move to pick up a rock (call it "E") this is only caused by P. The
   physical causes are in principle reducible to fundamental physics, and
   therefore mental causes are eliminated using this reductionist
   explanation. If P causes M and E, there is no overdetermination in the
   explanation for E.

Parallelism

   Psycho-physical parallelism is a very unusual view about the
   interaction between mental and physical events which was most
   prominently, and perhaps only truly, advocated by Gottfried Wilhelm von
   Leibniz. Like Malebranche and others before him, Leibniz recognized the
   weaknesses of Descartes' account of causal interaction taking place in
   a physical location in the brain. Malebranche decided that such a
   material basis of interaction between material and immaterial was
   impossible and therefore formulated his doctrine of occasionalism,
   stating that the interactions were really caused by the intervention of
   God on each individual occasion. Leibniz idea is that God has created a
   pre-established harmony such that it only seems as if physical and
   mental events cause, and are caused by, one another. In reality, mental
   causes only have mental effects and physical causes only have physical
   effects. Hence the term parallelism is used to describe this view.

Occasionalism

   Occasionalism argues that bodily events are the occasion of an act by
   the Creator causing a corresponding mental event, and vice versa. Any
   such view requires a theological structure as a premise.

Arguments for dualism

   Another one of Descartes' illustrations. The fire displaces the skin,
   which pulls a tiny thread, which opens a pore in the ventricle (F)
   allowing the "animal spirit" to flow through a hollow tube, which
   inflates the muscle of the leg, causing the foot to withdraw.
   Enlarge
   Another one of Descartes' illustrations. The fire displaces the skin,
   which pulls a tiny thread, which opens a pore in the ventricle (F)
   allowing the "animal spirit" to flow through a hollow tube, which
   inflates the muscle of the leg, causing the foot to withdraw.

   Arguments for dualism come in several varieties.

Subjective argument in support of dualism

   A very important argument against physicalism (and hence in favour of
   some sort of dualism) consists in the idea that the mental and the
   physical seem to have quite different and perhaps irreconcilable
   properties.

   Mental events have a certain subjective quality to them, whereas
   physical events obviously do not. For example, what does a burned
   finger feel like? What does sky blue look like? What does nice music
   sound like?

   Philosophers of mind call the subjective aspects of mental events
   qualia (or raw feels). There is something that it's like to feel pain,
   to see a familiar shade of blue, and so on; there are qualia involved
   in these mental events. And the claim is that qualia seem particularly
   difficult to reduce to anything physical.

   Frank Jackson formulated his famous knowledge argument based upon just
   such considerations. In this thought experiment, he asks us to consider
   a neuroscientist, Mary, who was born, and has lived all of her life, in
   a black and white room with a black and white television and computer
   monitor where she collects all the scientific data she possibly can on
   the nature of colors. Jackson asserts that as soon as Mary leaves the
   room, she will come to have new knowledge which she did not possess
   before: the knowledge of the experience of colors (i.e., what they are
   like). Although, by hypothesis, Mary had already known everyting there
   is to know about colors from an objective, scientific, third-person
   perspective, she never knew, according to Jackson, what it was like to
   see red, orange, green, etc.. If Mary really learns something new, it
   must be knowledge of something non-physical, since she already knew
   everything there is to know about the physical aspects of colour. David
   Lewis' response to this argument, now known as the ability argument, is
   that what Mary really came to know was simply the ability to recognize
   and identify colour sensations to which she had previously not been
   exposed. This argument fails because it confuses knowing how to do
   something with knowing something as something. Others have taken Lewis
   argument and attempted to modify it to argue that the ability that is
   learned consists in some sort of process of imagining or remembering.
   But both imagining and remembering are based on mental representation
   of what something was like. As a consequence, this argument begs the
   question against Jackson.

Special sciences argument

   This argument says that, if predicate dualism is correct, then there
   are special sciences which are irreducible to physics. These
   irreducible special sciences, which are the source of allegedly
   irreducible predicates, presumably differ from the hard sciences in
   that they are interest-relative. If they are interest-relative, then
   they must be dependent on the existence of minds which are capable of
   having interested perspectives. Psychology is, of course, the paragon
   of special sciences; therefore, it and its predicates must depend even
   more profoundly on the existence of the mental.

   Physics, at least ideally, sets out to tell us how the world is in
   itself, to carve up the world at its joints and describe it to us
   without the interference of individual perspectives or personal
   interests. On the other hand, such things as the patterns of the
   weather seen in meteorology or the behaviour of human beings are only
   of interest to human beings as such. Now, the point is that having a
   perspective on the world is a psychological state. Therefore, the
   special sciences presuppose the existence of minds which can have these
   states. If one is to avoid ontological dualism, then the mind that has
   a perspective must be part of the physical reality to which it applies
   its perspective. If this is the case, then in order to perceive the
   physical world as psychological, the mind must have a perspective on
   the physical. This, in turn, presupposes the existence of mind.

The zombie argument

   The zombie argument is based on a thought experiment proposed by David
   Chalmers. The basic idea is that one can imagine and therefore conceive
   the existence of one's body without any conscious states being
   associated with it.

   Chalmers' argument is that it seems very plausible 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, the move from conceivability
   to possibility is not such a large one.

Argument from personal identity

   This argument concerns the differences between the applicability of
   counterfactual conditionals to physical objects, on the one hand, and
   to conscious, personal agents on the other. In the case of any material
   object, e.g. a printer, we can formulate a series of counterfactuals in
   the following manner:

         1. This printer could have been made of straw.
         2. This printer could have been made of some other kind of
            plastics and vacuum-tube transistors.
         3. This printer could have been made of 95% of what it is
            actually made of and 5% vacuum-tube transistors, etc..

   Somewhere along the way from the printer's being made up exactly of the
   parts and materials which actually constitute it to the printer's being
   made up of some different matter at, say, 20%, the question of whether
   this printer is the same printer becomes a matter of arbitrary
   convention.

   Imagine the case of a person, Fredrick, who has a counterpart born from
   the same egg and a slightly genetically modified sperm. Imagine a
   series of counterfactual cases corresponding to the examples applied to
   the printer. Somewhere along the way, one is no longer sure about the
   identity of Frederick. In this latter case, it has been claimed,
   overlap of constitution cannot be applied to the identity of mind.

          "But while my present body can thus have its partial counterpart
          in some possible world, my present consciousness cannot. Any
          present state of consciousness that I can imagine either is or
          is not mine. There is no question of degree here."

   If the counterpart of Frederick, Frederickus, is 70% constituted of the
   same physical substance as Frederick, does this mean that it is also
   70% mentally identical with Frederick. Does it make sense to say that
   something is mentally 70% Frederick?

Arguments against dualism

Argument from causal interaction

   Varieties of dualism in which mind can causally affect matter have come
   under strenuous attack from different quarters, especially starting in
   the 20th century. How can something totally immaterial affect something
   totally material? That's the basic problem of causal interaction. We
   can analyze the problem here in three parts.

   First, it is not clear where the interaction would take place. For
   example, burning my fingers causes pain. Apparently there is some chain
   of events, leading from the burning of skin, to the stimulation of
   nerve endings, to something happening in the peripheral nerves of my
   body that lead to my brain, to something happening in a particular part
   of my brain, and finally resulting in the sensation of pain. But pain
   is not supposed to be spatially localizable. So where does the
   interaction take place? If you were to respond, "It takes place in the
   brain," then I might say, "But I thought pains weren't located
   anywhere." And you, as a dualist, might stick to your guns and say,
   "That's right, pains aren't located anywhere; but the brain event that
   immediately leads to the pain is located in the brain." But then we
   have a very strange causal relation on our hands. The cause is located
   in a particular place but the effect is not located anywhere. Perhaps
   this is not a devastating criticism.

   So let's look at a second problem about the interaction. Namely, how
   does the interaction take place? You might think, "Well, that's a
   matter for science -- scientists will eventually discover the
   connection between mental and physical events." But philosophers also
   have something to say about the matter: the very idea of a mechanism
   which explains the connection between the mental and the physical would
   be very strange, at best. Why would it be strange? Compare it to a
   mechanism that we do understand. Take a very simple causal relation,
   such as when the cue ball strikes the eight ball and causes it to go
   into the pocket. Here we can say that the cue ball has a certain amount
   of momentum as its mass moves across the pool table with some velocity,
   and then that momentum is transferred to the eight ball, which then
   heads toward the pocket. Now compare this to the situation in the
   brain, where we want to say a decision causes some neurons to fire and
   thus causes my body to move across the room. The intention "I will
   cross the room now," is a mental event and, as such, it does not have
   physical properties such as force. If it has no force, then how on
   earth could it cause any neuron to fire? Is it by magic? How could
   something without any physical properties have any physical effects at
   all?

   Here you might reply, as some philosophers have indeed replied, as
   follows: "Well sure, there is a mystery about how the interaction
   between mental and physical events can occur. But the fact that there
   is a mystery doesn't mean that there is no interaction. Plainly there
   is an interaction and plainly the interaction is between two totally
   different sorts of events." The problem with this response is that it
   does not seem to answer the full power of the objection.

   So let's try to explain the objection more precisely. Let's take as our
   example my decision to walk across the room. We say: my decision, a
   mental event, immediately causes a group of neurons in my brain to
   fire, a physical event, which ultimately results in my walking across
   the room. The problem is that if we have something totally nonphysical
   causing a bunch of neurons to fire, then there is no physical event
   which causes the firing. That means that some physical energy seems to
   have appeared out of thin air. Even if we say that my decision has some
   sort of mental energy, and that the decision causes the firing, we
   still haven't explained where the physical energy, for the firing, came
   from. It just seems to have popped into existence from nowhere.

Conservation of energy and causal closure

   One of the main objections to dualistic interactionism, as pointed out
   above, is that it is very difficult, if not impossible, to understand
   how two completely different types of substances (material and
   immaterial) are able to interact causally. One response to this is to
   point out that, perhaps, the causal interaction that takes place is not
   at all of the classical "billiard ball" type of Newtonian mechanics but
   instead involves energy, dark matter or some other such mysterious
   processes.

   Even if the latter is true, it has been argued, there is still a
   problem: such interactions seem to violate the fundamental laws of
   physics. If some external and unknown source of energy is responsible
   for the interactions, for example, then this would violate the law of
   the conservation of energy. On the other hand, the conservation laws
   only apply to closed and isolated systems and since human beings are
   not closed and isolated systems, an interactionist would argue, then
   the laws of conservation absolutely do not apply in this case.

   Along the same lines, some argue against dualistic interactionism that
   it violates a general heuristic principle of science: the causal
   closure of the physical world. But Mills has responded to this by
   pointing out that mental events may be causally overdetermined. Causal
   overdetermination means that some features of an effect may not be
   fully explained by its sufficient cause. For example, "the high pitched
   music caused the glass to break but this is the third time that that
   glass has broken in the last week." It is certain that the high-pitched
   music is the sufficient cause of the breaking of the glass, but it does
   not explain the feature of the event that is identified by the phrase
   "this is the third time this week...". That feature is causally
   related, in some sense, to the two prior events of the glasses having
   broken in the last week. In response, it has been pointed out that we
   should probably focus on the inherent or intrinsic features of
   situations or events, if they exist, and apply the idea of causal
   closure to just those specific features.

   Moreover, there is the question of determinism versus indeterminism. In
   quantum mechanisms, events at the microscopic level (at least) are
   indeterminate. The more precisely I can localize the position of an
   electron, the more imprecise becomes my ability to determine its
   angular momentum and vice-versa. Philosophers such as Karl Popper and
   John Eccles have theorized that such indeterminacy may apply even at
   the macroscopic scale. Most scientists, however, insist that the
   effects of such indeterminacy cancel each other out at larger levels.

Argument from brain damage

   This argument has been formulated by Paul Churchland, among others. The
   point is simply that when the brain undergoes some kind of damage
   (caused by automobile accidents, drug abuse or pathological diseases),
   it is always the case that the mental substance and/or properties of
   the person are significantly compromised. If the mind were a completely
   separate substance from the brain, how could it be possible that every
   single time the brain is injured, the mind is also injured? Indeed, it
   is very frequently the case that one can even predict and explain the
   kind of mental or psychological deterioration or change that human
   beings will undergo when specific parts of their brains are damaged. So
   the question for the dualist to try to confront is how can all of this
   be explained if the mind is a separate and immaterial substance from,
   or if its properties are ontologically independent of, the brain.

Argument from biological development

   Another common argument against dualism consists in the idea that since
   human beings (both phylogenetically and ontogenetically) begin their
   existence as entirely physical or material entities and since nothing
   outside of the domain of the physical is added later on the in course
   of development, then we must necessarily end up being fully developed
   material beings. Phylogenetically, the human species evolved, as did
   all other species, from a single cell made up of matter. Since all the
   events that later occurred which ended up in the formation of our
   species can be explained through the processes of random mutation and
   natural selection, the difficulty for the dualist is to explain where
   and why there could have intervened some non-material, non-physical
   event in this process of natural evolution. Ontogenetically, we begin
   life as a simple fertilized ovum. There is nothing non-material or
   mentalistic involved in conception, the formation of the blastula, the
   gastrula, and so on. Our development can be explained entirely in terms
   of the accumulation of matter through the processes of nutrition. Then
   where could a non-physical mind possibly come from?

Argument from simplicity

   The argument from simplicity is probably the simplest and also the most
   common form of argument against dualism of the mental. The dualist is
   always faced with the question of why anyone should find it necessary
   to believe in the existence of two, ontologically distinct, entities
   (mind and brain), when it seems possible and would make for a simpler
   thesis to test against scientific evidence, to explain the same events
   and properties in terms of one. It is a heuristic principle in science
   and philosophy not to assume the existence of more entities than is
   necessary for clear explanation and prediction (see Occam's razor).
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