Dualism and Mind

Dualists in the philosophy of mind emphasize the radical difference
between mind and matter. They all deny that the mind is the same as
the brain, and some deny that the mind is wholly a product of the
brain. This article explores the various ways that dualists attempt to
explain this radical difference between the mental and the physical
world. A wide range of arguments for and against the various dualistic
options are discussed.

Substance dualists typically argue that the mind and the body are
composed of different substances and that the mind is a thinking thing
that lacks the usual attributes of physical objects: size, shape,
location, solidity, motion, adherence to the laws of physics, and so
on. Substance dualists fall into several camps depending upon how they
think mind and body are related. Interactionists believe that minds
and bodies causally affect one another. Occasionalists and
parallelists, generally motivated by a concern to preserve the
integrity of physical science, deny this, ultimately attributing all
apparent interaction to God. Epiphenomenalists offer a compromise
theory, asserting that bodily events can have mental events as effects
while denying that the reverse is true, avoiding any threat to the
scientific law of conservation of energy at the expense of the common
sense notion that we act for reasons.

Property dualists argue that mental states are irreducible attributes
of brain states. For the property dualist, mental phenomena are
non-physical properties of physical substances. Consciousness is
perhaps the most widely recognized example of a non-physical property
of physical substances. Still other dualists argue that mental states,
dispositions and episodes are brain states, although the states cannot
be conceptualized in exactly the same way without loss of meaning.

Dualists commonly argue for the distinction of mind and matter by
employing Leibniz's Law of Identity, according to which two things are
identical if, and only if, they simultaneously share exactly the same
qualities. The dualist then attempts to identify attributes of mind
that are lacked by matter (such as privacy or intentionality) or vice
versa (such as having a certain temperature or electrical charge).
Opponents typically argue that dualism is (a) inconsistent with known
laws or truths of science (such as the aforementioned law of
thermodynamics), (b) conceptually incoherent (because immaterial minds
could not be individuated or because mind-body interaction is not
humanly conceivable), or (c) reducible to absurdity (because it leads
to solipsism, the epistemological belief that one's self is the only
existence that can be verified and known).

1. Dualism

The most basic form of dualism is substance dualism, which requires
that mind and body be composed of two ontologically distinct
substances. The term "substance" may be variously understood, but for
our initial purposes we may subscribe to the account of a substance,
associated with D. M. Armstrong, as what is logically capable of
independent existence. (Armstrong, 1968, p. 7). According to the
dualist, the mind (or the soul) is comprised of a non-physical
substance, while the body is constituted of the physical substance
known as matter. According to most substance dualists, mind and body
are capable of causally affecting each other. This form of substance
dualism is known as interactionism.

Two other forms of substance dualism are occasionalism and
parallelism. These theories are largely relics of history. The
occasionalist holds that mind and body do not interact. They may seem
to when,for example, we hit our thumb with a hammer and a painful and
distressing sensation occurs. Occassionalists, like Malebranche,
assert that the sensation is not caused by the hammer and nerves, but
instead by God. God uses the occasion of environmental happenings to
create appropriate experiences.

According to the parallelist, our mental and physical histories are
coordinated so that mental events appear to cause physical events (and
vice versa) by virtue of their temporal conjunction, but mind and body
no more interact than two clocks that are synchronized so that the one
chimes when hands of the other point out the new hour. Since this
fantastic series of harmonies could not possibly be due to mere
coincidence, a religious explanation is advanced. God does not
intervene continuously in creation, as the occasionalist holds, but
builds into creation a pre-established harmony that largely eliminates
the need for future interference.

Another form of dualism is property dualism. Property dualists claim
that mental phenomena are non-physical properties of physical
phenomena, but not properties of non-physical substances. Some forms
of epiphenomenalism fall into this category. According to
epiphenomenalism, bodily events or processes can generate mental
events or processes, but mental phenomena do not cause bodily events
or processes (or, on some accounts, anything at all, including other
mental states). (McLaughlin, p. 277) Whether an epiphenomenalist
thinks these mental epiphenomena are properties of the body or
properties of a non-physical mental medium determines whether the
epiphenomenalist is a property or substance dualist.

Still other dualists hold not that mind and body are distinct
ontologically, but our mentalistic vocabulary cannot be reduced to a
physicalistic vocabulary. In this sort of dualism, mind and body are
conceptually distinct, though the phenomena referred to by mentalistic
and physicalistic terminology are coextensive.

The following sections first discuss dualism as expounded by two of
its primary defenders, Plato and Descartes. This is followed by
additional arguments for and against dualism, with special emphasis on
substance dualism, the historically most important and influential
version of dualism.
2. Platonic Dualism in the Phaedo

The primary source for Plato's views on the metaphysical status of the
soul is the Phaedo, set on the final day of Socrates' life before his
self-administered execution. Plato (through the mouth of Socrates, his
dramatic persona) likens the body to a prison in which the soul is
confined. While imprisoned, the mind is compelled to investigate the
truth by means of the body and is incapable (or severely hindered) of
acquiring knowledge of the highest, eternal, unchanging, and
non-perceptible objects of knowledge, the Forms. Forms are universals
and represent the essences of sensible particulars. While encumbered
by the body, the soul is forced to seek truth via the organs of
perception, but this results in an inability to comprehend that which
is most real. We perceive equal things, but not Equality itself. We
perceive beautiful things but not Beauty itself. To achieve knowledge
or insight into the pure essences of things, the soul must itself
become pure through the practice of philosophy or, as Plato has
Socrates provocatively put it in the dialogue, through practicing
dying while still alive. The soul must struggle to disassociate itself
from the body as far as possible and turn its attention toward the
contemplation of intelligible but invisible things. Though perfect
understanding of the Forms is likely to elude us in this life (if only
because the needs of the body and its infirmities are a constant
distraction), knowledge is available to pure souls before and after
death, which is defined as the separation of the soul from the body.
a. The Argument From Opposites

Plato's Phaedo contains several arguments in support of his contention
that the soul can exist without the body. According to the first of
the Phaedo's arguments, the Argument from Opposites, things that have
an opposite come to be from their opposite. For example, if something
comes to be taller, it must come to be taller from having been
shorter; if something comes to be heavier, it must come to be so by
first having been lighter. These processes can go in either direction.
That is, things can become taller, but they also can become shorter;
things can become sweeter, but also more bitter. In the Phaedo,
Socrates notes that we awaken from having been asleep and go to sleep
from having been awake. Similarly, since dying comes from living,
living must come from dying. Thus, we must come to life again after we
die. During the interim between death and rebirth the soul exists
apart from the body and has the opportunity to glimpse the Forms
unmingled with matter in their pure and undiluted fullness. Death
liberates the soul, greatly increasing its apprehension of truth. As
such, the philosophical soul is unafraid to die and indeed looks
forward to death as to liberation.
b. The Argument From Recollection

A second argument from the Phaedo is the Argument from Recollection.
Socrates argues that the soul must exist prior to birth because we can
recollect things that could not have been learned in this life. For
example, according to Socrates we realize that equal things can appear
to be unequal or can be equal in some respects but not others. People
can disagree about whether two sticks are equal. They may disagree
about if they are equal in length, weight, color, or even whether they
are equally "sticks." The Form of Equality—Equality Itself—can never
be or appear unequal. According to Socrates, we recognize that the
sticks are unequal and that they are striving to be equal but are
nevertheless deficient in terms of their equality. Now, if we can
notice that the sticks are unequal, we must comprehend what Equality
is. Just as I could not recognize that a portrait was a poor likeness
of your grandfather unless I already knew what your grandfather looked
like, I cannot reccognize that the sticks are unequal by means of the
senses, without an understanding of the Form of Equality. We begin to
perceive at birth or shortly thereafter. Hence, the soul must have
existed prior to birth. It existed before it acquires a body. (A
similar argument is developed in Plato's Meno (81a-86b).
c. The Argument From Affinity

A third argument from the Phaedo is the Argument from Affinity.
Socrates claims that things that are composite are more liable to be
destroyed than things that are simple. The Forms are true unities and
therefore least likely ever to be annihilated. Socrates then posits
that invisible things such as Forms are not apt to be disintegrated,
whereas visible things, which all consist of parts, are susceptible to
decay and corruption. Since the body is visible and composite, it is
subject to decomposition. The soul, on the other hand, is invisible.
The soul also becomes like the Forms if it is steadfastly devoted to
their consideration and purifies itself by having no more association
with the body than necessary. Since the invisible things are the
durable things, the soul, being invisible, must outlast the body.
Further, the philosophical soul, that becomes Form-like, is immortal
and survives the death of the body.
d. Criticisms of the Platonic Arguments

Some of these arguments are challenged even in the Phaedo itself by
Socrates' friends Simmias and Cebes and the general consensus among
modern philosophers is that the arguments fail to establish the
immortality of the soul and its independence and separability from the
body. (Traces of the Affinity argument in a more refined form will be
observed in Descartes below). The Argument from Opposites applies only
to things that have an opposite and, as Aristotle notes, substances
have no contraries. Further, even if life comes from what is itself
not alive, it does not follow that the living human comes from the
union of a dead (i.e. separated) soul and a body. The principle that
everything comes to be from its opposite via a two-directional process
cannot hold up to critical scrutiny. Although one becomes older from
having been younger, there is no corresponding reverse process leading
the older to become younger. If aging is a uni-directional process,
perhaps dying is as well. Cats and dogs come to be from cats and dogs,
not from the opposites of these (if they have opposites). The
Arguments from Recollection and Affinity, on the other hand,
presuppose the existence of Forms and are therefore no more secure
than the Forms themselves (as Socrates notes in the Phaedo at 76d-e).

We turn now to Descartes' highly influential defense of dualism in the
early modern period.
3. Descartes' Dualism

The most famous philosophical work of René Descartes is the
Meditations on First Philosophy (1641). In the Sixth Meditation,
Descartes calls the mind a thing that thinks and not an extended
thing. He defines the body as an extended thing and not a thing that
thinks (1980, p. 93). "But what then am I? A thing that thinks. What
is that? A thing that doubts, understands affirms, denies, wills,
refuses, and which also imagines and senses." (1980, p. 63). He
expands on the notion of extension in the Fifth Meditation saying, "I
enumerate the [extended] thing's various parts. I ascribe to these
parts certain sizes, shapes, positions, and movements from place to
place; to these movements I ascribe various durations" (1980, p. 85).
Bodies, but not minds, are describable by predicates denoting entirely
quantifiable qualities and hence bodies are fit objects for scientific
study.

Having thus supplied us with the meanings of "mind" and "body,"
Descartes proceeds to state his doctrine: "I am present to my body not
merely in the way a seaman is present to his ship, but . . . I am
tightly joined and, so to speak, mingled together with it, so much so
that I make up one single thing with it" (1980, p. 94). The place
where this "joining" was believed by Descartes to be especially true
was the pineal gland—the seat of the soul. "Although the soul is
joined to the whole body, there is yet in the body a certain part in
which it seems to exercise its functions more specifically than in all
the others. . . I seem to find evidence that the part of the body in
which the soul exercises its functions immediately is. . . solely the
innermost part of the brain, namely, a certain very small gland."
(1952, p. 294). When we wish to "move the body in any manner, this
volition causes the gland to impel the spirits towards the muscles
which bring about this effect" (1952, p. 299). Conversely, the body is
also able to influence the soul. Light reflected from the body of an
animal and entering through our two eyes "form but one image on the
gland, which, acting immediately on the soul, causes it to see the
shape of the animal" (1952, p. 295-96).

It is clear, then, that Descartes held to a form of interactionism,
believing that mental events can sometimes cause bodily events and
that bodily events can sometimes cause mental events. (This reading of
Descartes-as-interactionist has recently been challenged. See Baker
and Morris (1996). Also, Daniel Garber suggests that Descartes is a
quasi-occasionalist, permitting minds to act on bodies, but invoking
God to explain the actions of inanimate bodies on each other and
phenomena where bodies act on minds, such as sensation. See Garber,
2001, ch. 10).
a. The Argument From Indivisibility

Descartes' primary metaphysical justification of the distinction of
mind and body is the Argument from Indivisibility. He writes, "there
is a great difference between a mind and a body, because the body, by
its very nature, is something divisible, whereas the mind is plainly
indivisible. . . insofar as I am only a thing that thinks, I cannot
distinguish any parts in me. . . . Although the whole mind seems to be
united to the whole body, nevertheless, were a foot or an arm or any
other bodily part amputated, I know that nothing would be taken away
from the mind. . ." (1980, p. 97). Decartes argues that the mind is
indivisible because it lacks extension. The body, as an object that
takes up space, can always be divided (at least conceptually), whereas
the mind is simple and non-spatial. Since the mind and body have
different attributes, they must not be the same thing, their "unity"
notwithstanding.

This Indivisibility Argument makes use of Leibniz's Law of Identity:
two things are the same if, and only if, they have all of the same
properties at the same time. More formally, x is identical to y if,
and only if, for any property p had by x at time t, y also has p at t,
and vice versa. Descartes uses Leibniz's Law to show that the mind and
body are not identical because they do not have all of the same
properties. An illustration (for present purposes a property can be
considered anything that may be predicated of a subject): If the man
with the martini is the mayor, it must be possible to predicate all
and only the same properties of both "the man" and "the mayor,"
including occupying (or having bodies that occupy) the same exact
spatial location at the same time.

Since divisibility may be predicated of bodies (and all of their
parts, such as brains) and may not be predicated of minds, Leibniz's
Law suggests that minds cannot be identical to bodies or any of their
parts or systems. Although it makes sense to speak of the left or
right half of the brain, it makes no sense to speak of half of a
desire, several pieces of a headache, part of joy, or two-thirds of a
belief. What is true of mental states is held to be true of the mind
that has the states as well. In the synopsis of the Meditations,
Descartes writes, "we cannot conceive of half a soul, as we can in the
case of any body, however small" (1980, p. 52). The mind has many
ideas, but they are all ideas of one indivisible mind.
b. Issues Raised by the Indivisibility Argument

John Locke argued that awareness is rendered discontinuous by
intervals of sleep, anesthesia, or unconsciousness. (Bk.II, ch.I,
sect.10). Is awareness then divisible? Locke suggests that the mind
cannot exhibit temporal discontinuity and also have thought as its
essence. But even if Descartes was wrong to consider the mind an
essentially thinking thing, the concept of mind is not reduced to
vacuity if some other, positive characteristic can be found by which
to define it. But what might that be? (Without some such means of
characterizing the mind it would be defined entirely negatively and we
would have no idea what it is).

Against Locke, Dualists can argue in several ways. (1) That the mind
has both conscious and unconscious thoughts and that Locke's argument
shows only that the mind is not always engaged in conscious
reflection, though it may be perpetually busy at the unconscious
level. Locke argues that such a maneuver creates grave difficulties
for personal identity (Bk.II, Ch.I, sect.11), however, and denies that
thoughts can exist unperceived. (2) Dualists can argue that the soul
always thinks, but that the memory fails to preserve those thoughts
when asleep or under anesthesia. (3) Dualists can argue that the
Lockean observation is not relevant to the Argument from
Indivisibility because the discontinuity Locke identifies in
consciousness is not a spatial discontinuity but a temporal one. The
Argument from Indivisibility seeks to show that bodies but not minds
are spatially divisible and that argument is not rebutted by pointing
out that consciousness is temporally divisible. (Indeed, if minds are
temporally divisible and bodies are not, we have an argument for
dualism of a different sort).

David Hume, on the other hand, questioned of what the unity of
consciousness might consist. The Indivisibility Argument suggests that
the mind is a simple unity. Hume finds no reason to grant or assume
that the diversity of our experiences (whether visual perception, pain
or active thinking and mathematical apprehension) constitute a unity
rather than a diversity. For Hume, all introspection reveals is the
presence of various impressions and ideas, but does not reveal a
subject in which those ideas inhere. Accordingly, if observation is to
yield knowledge of the self, the self can consist in nothing but a
bundle of perceptions. Even talk of a "bundle" is misleading if that
suggests an empirically discoverable internal unity. Thus, Descartes'
commitment to a res cogitans or thing which thinks is unfounded and
substance dualism is undermined. (For a contrary view on what
constitutes the unity of the self, see Madell's view that, "What
unites all of my experiences…is simply that they all have the
irreducible and unanalyzable property of 'mineness,'" in Nagel, 1986,
p. 34, n. 5).

Immanuel Kant replied to Hume that we must suppose or posit the unity
of the ego (which he called the "transcendental unity of
apperception") as a preliminary to all experience since without such a
unity the manifold of sense-data (or "sensibility") could not
constitute, for example, the experience of seeing a clock. However,
Kant agreed that we must not mistake the unity of apperception for the
perception of unity—that is, the perception of a unitary thing or
substance. Kant also argued that there is little reason to suppose
that the mind or ego cannot be destroyed despite its unity since its
powers may gradually attenuate to the point where they simply fade
away. The mind need not be separated into non-physical granules to be
destroyed since it can suffer a kind of death through loss of its
powers. Awareness, perception, memory and the like admit of degrees.
If the degree of consciousness decreases to zero, then the mind is
effectively annihilated. Even if, as Plato and Descartes agree, the
mind is not divisible, it does not follow that it survives (or could
survive) separation from the body. Additionally, if the mind is
neither physical nor identical to its inessential characteristics
(1980, p. 53), it is impossible to distinguish one mind from another.
Kant argues that two substances that are otherwise identical can be
differentiated only by their spatial locations. If minds are not
differentiated by their contents and have no spatial positions to
distinguish them, there remains no basis for individuating their
identities. (On numerically individuating non-physical substances, see
Armstrong, 1968, pp. 27-29. For a general discussion of whether the
self is a substance, see Shoemaker, 1963, ch. 2).
c. The Argument From Indubitability

Descartes' other major argument for dualism in the Meditations derives
from epistemological considerations. After taking up his celebrated
method of doubt, which commits him to reject as false anything that is
in the slightest degree uncertain, Descartes finds that the entirety
of the physical world is uncertain. Perhaps, after all, it is nothing
but an elaborate phantasm wrought by an all-powerful and infinitely
clever, but deceitful, demon. Still, he cannot doubt his own
existence, since he must exist to doubt. Because he thinks, he is. But
he cannot be his body, since that identity is doubtful and possibly
altogether false. Therefore, he is a non-bodily "thinking thing," or
mind. As Richard Rorty puts it: "If we look in Descartes for a common
factor which pains, dreams, memory-images, and veridical and
hallucinatory perceptions share with concepts of (and judgments about)
God, number, and the ultimate constituents of matter, we find no
explicit doctrine. . . . The answer I would give to the question 'What
did Descartes find?' is 'Indubitability'" (1979 p. 54). In sum, I
cannot doubt the existence of my mind, but I can doubt the existence
of my body. Since what I cannot doubt cannot be identical to what I
can doubt (by Leibniz's Law), mind and body are not identical and
dualism is established.

This argument is also featured in Descartes' Discourse on Method part
four: "[S]eeing that I could pretend that I had no body and that there
was no world nor any place where I was, but that I could not pretend,
on that account, that I did not exist; and that, on the contrary, from
the very fact that I thought about doubting the truth of other things,
it followed very evidently and very certainly that I existed. . . .
From this I knew that I was a substance the whole essence or nature of
which was merely to think, and which, in order to exist, needed no
place and depended on no material things. Thus this 'I,' that is, the
soul through which I am what I am, is entirely distinct from the body.
. ." (1980, p. 18).

The Argument from Indubitability has been maligned in the
philosophical literature from the very beginning. Most famously,
Arnauld comments in the objections originally published with the
Meditations that, "Just as a man errs in not believing that the
equality of the square on its base to the squares on its sides belongs
to the nature of that triangle, which he clearly and distinctly knows
to be right angled, so why am I perhaps not in the wrong in thinking
that nothing else belongs to my nature which I clearly and distinctly
know to be something that thinks, except that fact that I am this
thinking being? Perhaps it also belongs to my essence to be something
extended." (1912, p. 84). Suppose that I cannot doubt whether a given
figure is a triangle, but can doubt whether its interior angles add up
to two right angles. It does not follow from this that the number of
degrees in triangles may be more or less than 180. This is because the
doubt concerning the number of degrees in a triangle is a property of
me, not of triangles. Similarly, I may doubt that my body is not a
property of my body, believing it to be a property of whatever part of
me it is that doubts, and that "whatever" may be something extended.

The dualist can reply in two ways. First, he or she may argue that,
while doubting the body is not a property of bodies, being doubtable
is a property of bodies. Since bodies have the property of being
doubtable, and minds do not, by Leibniz's Law the diversity of the two
is established. Second, the dualist may reply that it is always
possible to doubt whether the figure before me is a triangle. As such,
Arnauld's supposedly parallel argument is not parallel at all. Similar
objections are open against other, more recent rebuttals to Descartes'
argument. Consider, for example, the following parallel argument from
Paul Churchland (1988, p. 32): I cannot doubt that Mohammed Ali was a
famous heavyweight boxer but can doubt that Cassius Clay was a famous
heavyweight boxer. Following Descartes, it ought to be that Ali is not
Clay (though in fact Clay was a famous heavyweight and identical to
Ali). By way of reply, surely it is possible for an evil demon to
deceive me about whether Mohammed Ali was a famous heavyweight boxer.
So, the dualist might insist, the case of mind is unique in its
immunity from doubt. It is only with reference to our own mental
states that we can be said to know incorrigibly.
d. The Real Distinction Argument

A third argument in the Meditations maintains that the mind and body
must really be separate because Descartes can conceive of the one
without the other. Since he can clearly and distinctly understand the
body without the mind and vice versa, God could really have created
them separately. But if the mind and body can exist independently,
they must really be independent, for nothing can constitute a part of
the essence of a thing that can be absent without the thing itself
ceasing to be. If the essence of the mind is incorporeal, so must be
the mind itself.
4. Other Leibniz's Law Arguments for Dualism
a. Privacy and First Person Authority

As noted earlier, dualists have argued for their position by employing
Leibniz's Law in many ingenious ways. The general strategy is to
identify some property or feature indisputably had by mental phenomena
but not attributable in any meaningful way to bodily or nervous
phenomena, or vice versa. For example, some have suggested that mental
states are private in the sense that only those who possess them can
know them directly. If I desire an apple, I know that I have this
desire "introspectively." Others can know of my desire only by means
of my verbal or non-verbal behavior or, conceivably, by inspection of
my brain. (The latter assumes a correlation, if not an identity,
between nervous and mental states or events). My linguistic, bodily
and neural activities are public in the sense that anyone suitably
placed can observe them. Since mental states are private to their
possessors, but brain states are not, mental states cannot be
identical to brain states. (Rey pp. 55-56).

A closely related argument emphasizes that my own mental states are
knowable without inference; I know them "immediately." (Harman, 1973,
pp. 35-37). Others can know my mental states only by making inferences
based on my verbal, non-verbal or neurophysiological activity. You may
infer that I believe it will rain from the fact that I am carrying an
umbrella, but I do not infer that I believe it will rain from noticing
that I am carrying an umbrella. I do not need to infer my mental
states because I know them immediately. Since mental states are
knowable without inference in the first person case, but are knowable
(or at least plausibly assigned) only by inference in the third person
case, we have an authority or incorrigibility with reference to our
own mental states that no one else could have. Since beliefs about the
physical world are always subject to revision (our inferences or
theories could be mistaken), mental states are not physical states.
b. Intentionality

Some mental states exhibit intentionality. Intentional mental states
include, but are not limited to, intendings, such as plans to buy milk
at the store. They are states that are about, of, for, or towards
things other than themselves. Desires, beliefs, loves, hates,
perceptions and memories are common intentional states. For example, I
may have a desire for an apple; I may have love for or towards my
neighbor; I may have a belief about republicans or academics; or I may
have memories of my grandfather.

The dualist claims that brain states, however, cannot plausibly be
ascribed intentionality. How can a pattern of neural firings be of or
about or towards anything other than itself? As a purely physical
event, an influx of sodium ions through the membrane of a neural cell
creating a polarity differential between the inside and outside of the
cell wall, and hence an electrical discharge, cannot be of Paris,
about my grandfather, or for an apple. [Although Brentano goes further
than most contemporary philosophers in regarding all mental phenomena
as intentional, he argues that "the reference to something as an
object is a distinguishing characteristic of all mental phenomena. No
physical phenomena exhibits anything similar." (Brentano, 1874/1973,
p. 97, quoted in Rey, 1997, p. 23).] Thus, by Leibniz's Law, if minds
are capable of intentional states and bodies are not, minds and bodies
must be distinct. (Taylor, pp. 11-12; Rey pp. 57-59).
c. Truth and Meaning

Another attempt to derive dualism by means of Leibniz's Law observes
that some mental states, especially beliefs, have truth-values. My
belief that it will rain can be either true or false. But, the dualist
may urge, as a purely physical event, an electrical or chemical
discharge in the brain cannot be true or false. Indeed, it lacks not
only truth, but also linguistic meaning. Since mental states such as
beliefs possess truth-value and semantics, it seems incoherent to
attribute these properties to bodily states. Thus, mental states are
not bodily states. Presumably, then, the minds that have these states
are also non-physical. (Churchland, 1988, p. 30; Taylor, 1983, p. 12).
d. Problems with Leibniz's Law Arguments for Dualism

Although each of these arguments for dualism may be criticized
individually, they are typically thought to share a common flaw: they
assume that because some aspect of mental states, such as privacy,
intentionality, truth, or meaning cannot be attributed to physical
substances, they must be attributable to non-physical substances. But
if we do not understand how such states and their properties can be
generated by the central nervous system, we are no closer to
understanding how they might be produced by minds. (Nagel, 1986, p.
29). The question is not, "How do brains generate mental states that
can only be known directly by their possessors?" Rather, the relavent
question is "How can any such thing as a substance, of whatever sort,
do these things?" The mystery is as great when we posit a mind as the
basis of these operations or capacities as when we attribute them to
bodies. Dualists cannot explain the mechanisms by which souls generate
meaning, truth, intentionality or self-awareness.Thus, dualism creates
no explanatory advantage. As such, we should use Ockham's razor to
shave off the spiritual substance, because we ought not to multiply
entities beyond what is necessary to explain the phenomena. Descartes'
prodigious doubt notwithstanding, we have excellent reasons for
thinking that bodies exist. If the only reasons for supposing that
non-physical minds exist are the phenomena of intentionality, privacy
and the like, then dualism unnecessarily complicates the metaphysics
of personhood.

On the other hand, dualists commonly argue that it makes no sense to
attribute some characteristics of body to mind; that to do so is to
commit what Gilbert Ryle called a "category mistake." For example, it
makes perfect sense to ask where the hypothalamus is, but not, in
ordinary contexts, to ask where my beliefs are. We can ask how much
the brain weighs, but not how much the mind weighs. We can ask how
many miles per hour my body is moving, but not how many miles per hour
my mind is moving. Minds are just not the sorts of things that can
have size, shape, weight, location, motion, and the other attributes
that Descartes ascribes to extended reality. We literally could not
understand someone who informed us that the memories of his last
holiday are two inches behind the bridge of his nose or that his
perception of the color red is straight back from his left eye. If
these claims are correct, then some Leibniz's Law arguments for
dualism are not obviously vulnerable to the critique above.
5. The Free Will and Moral Arguments

Another argument for dualism claims that dualism is required for free
will. If dualism is false, then presumably materialism, the thesis
that humans are entirely physical beings, is true. (We set aside
consideration of idealism—the thesis that only minds and ideas exist).
If materialism were true, then every motion of bodies should be
determined by the laws of physics, which govern the actions and
reactions of everything in the universe. But a robust sense of freedom
presupposes that we are free, not merely to do as we please, but that
we are free to do otherwise than as we do. This, in turn, requires
that the cause of our actions not be fixed by natural laws. Since,
according to the dualist, the mind is non-physical, there is no need
to suppose it bound by the physical laws that govern the body. So, a
strong sense of free will is compatible with dualism but incompatible
with materialism. Since freedom in just this sense is required for
moral appraisal, the dualist can also argue that materialism, but not
dualism, is incompatible with ethics. (Taylor, 1983, p. 11; cf. Rey,
1997, pp. 52-53). This, the dualist may claim, creates a strong
presumption in favor of their metaphysics.

This argument is sometimes countered by arguing that free will is
actually compatible with materialism or that even if the dualistic
account of the will is correct, it is irrelevant because no volition
on the part of a non-physical substance could alter the course of
nature anyway. As Bernard Williams puts it, "Descartes' distinction
between two realms, designed to insulate responsible human action from
mechanical causation, insulated the world of mechanical causation,
that is to say, the whole of the external world, from responsible
human action. Man would be free only if there was nothing he could
do." (1966, p. 7). Moreover, behaviorist opponents argue that if
dualism is true, moral appraisal is meaningless since it is impossible
to determine another person's volitions if they are intrinsically
private and otherworldly.
6. Property Dualism

Property dualists claim that mental phenomena are non-physical
properties of physical phenomena, but not properties of non-physical
substances. Property dualists are not committed to the existence of
non-physical substances, but are committed to the irreducibility of
mental phenomena to physical phenomena.

An argument for property dualism, derived from Thomas Nagel and Saul
Kripke, is as follows: We can assert that warmth is identical to mean
kinetic molecular energy, despite appearances, by claiming that warmth
is how molecular energy is perceived or manifested in consciousness.
Minds detect molecular energy by experiencing warmth; warmth "fixes
the reference" of heat. ("Heat" is a rigid designator of molecular
motion; "the sensation of heat" is a non-rigid designator.) Similarly,
color is identical to electromagnetic reflectance efficiencies,
inasmuch as color is how electromagnetic wavelengths are processed by
human consciousness. In these cases, the appearance can be
distinguished from the reality. Heat is molecular motion, though it
appears to us as warmth. Other beings, for example, Martians, might
well apprehend molecular motion in another fashion. They would grasp
the same objective reality, but by correlating it with different
experiences. We move toward a more objective understanding of heat
when we understand it as molecular energy rather than as warmth. in
our case, or as whatever it appears to them to be in theirs.
Consciousness itself, however, cannot be reduced to brain activity
along analogous lines because we should then need to say that
consciousness is how brain activity is perceived in consciousness,
leaving consciousness unreduced. Put differently, when it comes to
consciousness, the appearance is the reality. Therefore, no reduction
is possible. Nagel writes:

Experience . . . does not seem to fit the pattern. The idea of
moving from appearance to reality seems to make no sense here. What is
the analogue in this case to pursuing a more objective understanding
of the same phenomena by abandoning the initial subjective viewpoint
toward them in favor of another that is more objective but concerns
the same thing? Certainly it appears unlikely that we will get closer
to the real nature of human experience by leaving behind the
particularity of our human point of view and striving for a
description in terms accessible to beings that could not imagine what
it was like to be us. (Nagel 1974; reprinted in Block et. al. p. 523).

Consciousness is thus sui generis (of its own kind), and successful
reductions elsewhere should give us little confidence when it comes to
experience.

Some property dualists, such as Jaegwon Kim, liken "having a mind" to
"a property, capacity, or characteristic that humans and some higher
animals possess in contrast with things like pencils and rocks. . . .
Mentality is a broad and complex property." (Kim, 1996, p. 5). Kim
continues: "[Some properties] are physical, like having a certain mass
or temperature, being 1 meter long, and being heavier than. Some
things—in particular, persons and certain biological organisms—can
also instantiate mental properties, like being in pain and liking the
taste of avocado." (p. 6). Once we admit the existence of mental
properties, we can inquire into the nature of the relationship between
mental and physical properties. According to the supervenience thesis,
there can be no mental differences without corresponding physical
differences. If, for example, I feel a headache, there must be some
change not only in my mental state, but also in my body (presumably,
in my brain). If Mary is in pain, but Erin is not, then, according to
the supervenience thesis, there must be a physical difference between
Mary and Erin. For example, Mary's c-fibers might are firing and
Erin's are not. If this is true, it is possible to argue for a type of
property dualism by arguing that some mental states or properties,
especially the phenomenal aspects of consciousness, do not "supervene
on" physical states or properties in regular, lawlike ways. (Kim, p.
169).

Why deny supervenience? Because it seems entirely conceivable that
there could exist a twin Earth where all of the physical properties
that characterize the actual world are instantiated and are
interrelated as they are here, but where the inhabitants are "zombies"
without experience, or where the inhabitants have inverted qualia
relative to their true-Earth counterparts. If it is possible to have
mental differences without physical differences, then mental
properties cannot be identical to or reducible to physical properties.
They would exist as facts about the world over and above the purely
physical facts. Put differently, it always makes sense to wonder "why
we exist and not zombies." (Chalmers, 1996, p. 110). (Kim, 169 and
following.; Kripke, 1980, throughout; Chalmers, 1996, throughout, but
esp. chs. 3 & 4).

Some have attempted to rebut this "conceivability argument" by noting
that the fact that we can ostensibly imagine such a zombie world does
not mean that it is possible. Without the actual existence of such a
world, the argument that mental properties do not supervene on
physical properties fails.

A second rebuttal avers that absent qualia thought experiments (and
inverted spectra though experiments) only support property dualism if
we can imagine these possibilities obtaining. Perhaps we think we can
conceive a zombie world, when we really can't. We may think we can
conceive of such a world but attempts to do so do not actually achieve
such a conception.

To illustrate, suppose that Goldbach's Conjecture is true. If it is,
its truth is necessary. If, then, someone thought that they imagined a
proof that the thesis is false, they would be conceiving the falsity
of what is in reality a necessary truth. This is implausible. What we
should rather say in such a case is that the person was mistaken, and
that what they imagined false was not Goldbach's Conjecture after all,
or that the "proof" that was imagined was in fact no proof, or that
what they were really imagining was something like an excited
mathematician shouting, "Eureka! So it's false then!" Perhaps it is
likewise when we "conceive" a zombie universe. We may be mistaken
about what it is that we are actually "picturing" to ourselves.
Against this objection, however, one could argue that there are
independent grounds for thinking that the truth-value of Goldbach's
theorem is necessary and no independent reasons for thinking that
Zombie worlds are impossible; therefore, the dualist deserves the
benefit of the doubt.

But perhaps the physicalist can come up with independent reasons for
supposing that the dualist has failed to imagine what she claims. The
physicalist can point, for example, to successful reductions in other
areas of science. On the basis of these cases she can argue the
implausibility of supposing that, uniquely, mental phenomena resist
reduction to the causal properties of matter. That is, an inductive
argument for reduction outweighs a conceivability argument against
reduction. And in that case, the dualist must do more than merely
insist that she has correctly imagined inverted spectra in isomorphic
individuals. (For useful discussions of some of these issues, see Tye
1986 and Horgan 1987.)
7. Objections to Dualism Motivated by Scientific Considerations

The Ockham's Razor argument creates a strong methodological
presumption against dualism, suggesting that the mind-body split
multiplies entities unnecessarily in much the way that a demon theory
of disease complicates the metaphysics of medicine compared to a germ
theory. It is often alleged, more broadly, that dualism is
unscientific and renders impossible any genuine science of mind or
truly empirical psychology.
a. Arguments from Human Development

Those eager to defend the relevance of science to the study of mind,
such as Paul Churchland, have argued that dualism is inconsistent with
the facts of human evolution and fetal development. (1988, pp. 27-28;
see also Lycan, 1996, p. 168). According to this view, we began as
wholly physical beings. This is true of the species and the individual
human. No one seriously supposes that newly fertilized ova are imbued
with minds or that the original cell in the primordial sea was
conscious. But from those entirely physical origins, nothing
non-physical was later added. We can explain the evolution from the
unicellular stage to present complexities by means of random mutations
and natural selection in the species case and through the accretion of
matter through nutritional intake in the individual case. But if we,
as species or individuals, began as wholly physical beings and nothing
nonphysical was later added, then we are still wholly physical
creatures. Thus, dualism is false. The above arguments are only as
strong as our reasons for thinking that we began as wholly material
beings and that nothing non-physical was later added. Some people,
particularly the religious, will object that macro-evolution of a
species is problematic or that God might well have infused the
developing fetus with a soul at some point in the developmental
process (traditionally at quickening). Most contemporary philosophers
of mind put little value in these rejoinders.
b. The Conservation of Energy Argument

Others argue that dualism is scientifically unacceptable because it
violates the well-established principle of the conservation of energy.
Interactionists argue that mind and matter causally interact. But if
the spiritual realm is continually impinging on the universe and
effecting changes, the total level of energy in the cosmos must be
increasing or at least fluctuating. This is because it takes physical
energy to do physical work. If the will alters states of affairs in
the world (such as the state of my brain), then mental energy is
somehow converted into physical energy. At the point of conversion,
one would anticipate a physically inexplicable increase in the energy
present within the system. If it also takes material energy to
activate the mind, then "physical energy would have to vanish and
reappear inside human brains." (Lycan, 1996, 168).

The dualists' basically have three ways of replying. First, they could
deny the sacredness of the principle of the conservation of energy.
This would be a desperate measure. The principle is too well
established and its denial too ad hoc. Second, the dualist might offer
that mind does contribute energy to our world, but that this addition
is so slight, in relation to our means of detection, as to be
negligible. This is really a re-statement of the first reply above,
except that here the principle is valid in so far as it is capable of
verification. Science can continue as usual, but it would be
unreasonable to extend the law beyond our ability to confirm it
experimentally. That would be to step from the empirical to the
speculative—the very thing that the materialist objects to in dualism.
The third option sidesteps the issue by appealing to another, perhaps
equally valid, principle of physics. Keith Campbell (1970) writes:

The indeterminacy of quantum laws means that any one of a range of
outcomes of atomic events in the brain is equally compatible with
known physical laws. And differences on the quantum scale can
accumulate into very great differences in overall brain condition. So
there is some room for spiritual activity even within the limits set
by physical law. There could be, without violation of physical law, a
general spiritual constraint upon what occurs inside the head. (p. 54)

Mind could act upon physical processes by "affecting their course but
not breaking in upon them" (1970, p. 54). If this is true, the dualist
could maintain the conservation principle but deny a fluctuation in
energy because the mind serves to "guide" or control neural events by
choosing one set of quantum outcomes rather than another. Further, it
should be remembered that the conservation of energy is designed
around material interaction; it is mute on how mind might interact
with matter. After all, a Cartesian rationalist might insist, if God
exists we surely wouldn't say that He couldn't do miracles just
because that would violate the first law of thermodynamics, would we?
c. Problems of Interaction

The conservation of energy argument points to a more general complaint
often made against dualism: that interaction between mental and
physical substances would involve a causal impossibility. Since the
mind is, on the Cartesian model, immaterial and unextended, it can
have no size, shape, location, mass, motion or solidity. How then can
minds act on bodies? What sort of mechanism could convey information
of the sort bodily movement requires, between ontologically autonomous
realms? To suppose that non-physical minds can move bodies is like
supposing that imaginary locomotives can pull real boxcars. Put
differently, if mind-body interaction is possible, every voluntary
action is akin to the paranormal power of telekinesis, or "mind over
matter." If minds can, without spatial location, move bodies, why can
my mind move immediately only one particular body and no others?
Confronting the conundrum of interaction implicit in his theory,
Descartes posited the existence of "animal spirits" somewhat subtler
than bodies but thicker than minds. Unfortunately, this expedient
proved a dead-end, since it is as incomprehensible how the mind could
initiate motion in the animal spirits as in matter itself.

These problems involved in mind-body causality are commonly considered
decisive refutations of interactionism. However, many interesting
questions arise in this area. We want to ask: "How is mind-body
interaction possible? Where does the interaction occur? What is the
nature of the interface between mind and matter? How are volitions
translated into states of affairs? Aren't minds and bodies
insufficiently alike for the one to effect changes in the other?"

It is useful to be reminded, however, that to be bewildered by
something is not in itself to present an argument against, or even
evidence against, the possibility of that thing being a matter of
fact. To ask "How is it possible that . . . ?" is merely to raise a
topic for discussion. And if the dualist doesn't know or cannot say
how minds and bodies interact, what follows about dualism? Nothing
much. It only follows that dualists do not know everything about
metaphysics. But so what? Psychologists, physicists, sociologists, and
economists don't know everything about their respective disciplines.
Why should the dualist be any different? In short, dualists can argue
that they should not be put on the defensive by the request for
clarification about the nature and possibility of interaction or by
the criticism that they have no research strategy for producing this
clarification.

The objection that minds and bodies cannot interact can be the
expression of two different sorts of view. On the one hand, the
detractor may insist that it is physically impossible that minds act
on bodies. If this means that minds, being non-physical, cannot
physically act on bodies, the claim is true but trivial. If it means
that mind-body interaction violates the laws of physics (such as the
first law of thermodynamics, discussed above), the dualist can reply
that minds clearly do act on bodies and so the violation is only
apparent and not real. (After all, if we do things for reasons, our
beliefs and desires cause some of our actions). If the materialist
insists that we are able to act on our beliefs, desires and
perceptions only because they are material and not spiritual, the
dualist can turn the tables on his naturalistic opponents and ask how
matter, regardless of its organization, can produce conscious
thoughts, feelings and perceptions. How, the dualist might ask, by
adding complexity to the structure of the brain, do we manage to leap
beyond the quantitative into the realm of experience? The relationship
between consciousness and brain processes leaves the materialist with
a causal mystery perhaps as puzzling as that confronting the dualist.

On the other hand, the materialist may argue that it is a conceptual
truth that mind and matter cannot interact. This, however, requires
that we embrace the rationalist thesis that causes can be known a
priori. Many prefer to assert that causation is a matter for empirical
investigation. We cannot, however, rule out mental causes based solely
on the logic or grammar of the locutions "mind" and "matter."
Furthermore, in order to defeat interactionism by an appeal to causal
impossibility, one must first refute the Humean equation of causal
connection with regularity of sequence and constant conjunction.
Otherwise, anything can be the cause of anything else. If volitions
are constantly conjoined with bodily movements and regularly precede
them, they are Humean causes. In short, if Hume is correct, we cannot
refute dualism a priori by asserting that transactions between minds
and bodies involve links where, by definition, none can occur.

Some, such as Ducasse (1961, 88; cf. Dicker pp. 217-224), argue that
the interaction problem rests on a failure to distinguish between
remote and proximate causes. While it makes sense to ask how
depressing the accelerator causes the automobile to speed up, it makes
no sense to ask how pressing the accelerator pedal causes the pedal to
move. We can sensibly ask how to spell a word in sign language, but
not how to move a finger. Proximate causes are "basic" and analysis of
them is impossible. There is no "how" to basic actions, which are
brute facts. Perhaps the mind's influence on the pineal gland is basic
and brute.

One final note: epiphenomenalism, like occasionalism and parallelism,
is a dualistic theory of mind designed, in part, to avoid the
difficulties involved in mental-physical causation (although
occasionalism was also offered by Malebranche as an account of
seemingly purely physical causation). According to epiphenomenalism,
bodies are able to act on minds, but not the reverse. The causes of
behavior are wholly physical. As such, we need not worry about how
objects without mass or physical force can alter behavior. Nor need we
be concerned with violations of the conservation of energy principle
since there is little reason to suppose that physical energy is
required to do non-physical work. If bodies affect modifications in
the mental medium, that need not be thought to involve a siphoning of
energy from the world to the psychic realm. On this view, the mind may
be likened to the steam from a train engine; the steam does not affect
the workings of the engine but is caused by it. Unfortunately,
epiphenomenalism avoids the problem of interaction only at the expense
of denying the common-sense view that our states of mind have some
bearing on our conduct. For many, epiphenomenalism is therefore not a
viable theory of mind. (For a defense of the common-sense claim that
beliefs and attitudes and reasons cause behavior, see Donald
Davidson.)
d. The Correlation and Dependence Arguments

The correlation and dependence argument against dualism begins by
noting that there are clear correlations between certain mental events
and neural events (say, between pain and a-fiber or c-fiber
stimulation). Moreover, as demonstrated in such phenomena as memory
loss due to head trauma or wasting disease, the mind and its
capacities seem dependent upon neural function. The simplest and best
explanation of this dependence and correlation is that mental states
and events are neural states and events and that pain just is c-fiber
stimulation. (This would be the argument employed by an identity
theorist. A functionalist would argue that the best explanation for
the dependence and correlation of mental and physical states is that,
in humans, mental states are brain states functionally defined).

Descartes himself anticipated an objection like this and argued that
dependence does not strongly support identity. He illustrates by means
of the following example: a virtuoso violinist cannot manifest his or
her ability if given an instrument in deplorable or broken condition.
The manifestation of the musician's ability is thus dependent upon
being able to use a well-tuned instrument in proper working order. But
from the fact that the exhibition of the maestro's skill is impossible
without a functioning instrument, it hardly follows that being skilled
at playing the violin amounts to no more than possessing such an
instrument. Similarly, the interactionist can claim that the mind uses
the brain to manifest it's abilities in the public realm. If, like the
violin, the brain is in a severely diseased or injurious state, the
mind cannot demonstrate its abilities; they of necessity remain
private and unrevealed. However, for all we know, the mind still has
its full range of abilities, but is hindered in its capacity to
express them. As for correlation, interactionism actually predicts
that mental events are caused by brain events and vice versa, so the
fact that perceptions are correlated with activity in the visual
cortex does not support materialism over this form of dualism.
Property dualists agree with the materialists that mental phenomena
are dependent upon physical phenomena, since the fomer are
(non-physical) attributes of the latter. Materialists are aware of
these dualist replies and sometimes invoke Ockham's razor and the
importance of metaphysical simplicity in arguments to the best
explanation. (See Churchland, 1988, p. 28). Other materialist
responses will not be considered here.
8. The Problem of Other Minds

The problem of how we can know other minds has been used as follows to
refute dualism. If the mind is not publicly observable, the existence
of minds other than our own must be inferred from the behavior of the
other person or organism. The reliability of this inference is deeply
suspect, however, since we only know that certain mental states cause
characteristic behavior from our own case. To extrapolate to the
population as a whole from the direct inspection of a single example,
our own case, is to make the weakest possible inductive
generalization. Hence, if dualism is true, we cannot know that other
people have minds at all. But common sense tell us that others do have
minds. Since common sense can be trust, dualism is false.

This problem of other minds, to which dualism leads so naturally, is
often used to support rival theories such as behaviorism, the
mind-brain identity theory, or functionalism (though functionalists
sometimes claim that their theory is consistent with dualism). Since
the mind, construed along Cartesian lines, leads to solipsism (that
is, to the epistemological belief that one's self is the only
existence that can be verified and known), it is better to
operationalize the mind and define mental states behaviorally,
functionally, or physiologically. If mental states are just behavioral
states, brain states, or functional states, then we can verify that
others have mental states on the basis of publicly observable
phenomena, thereby avoiding skepticism about other selves.

Materialist theories are far less vulnerable to the problem of other
minds than dualist theories, though even here other versions of the
problem stubbornly reappear. Deciding to define mental states
behaviorally does not mean that mental states are behavioral, and it
is controversial whether attempts to reduce mentality to behavioral,
brain, or functional states have been successful. Moreover, the
"Absent Qualia" argument claims that it is perfectly imaginable and
consistent with everything that we know about physiology that, of two
functionally or physiologically isomorphic beings, one might be
conscious and the other not. Of two outwardly indistinguishable
dopplegangers, one might have experience and the other none. Both
would exhibit identical neural activity; both would insist that they
can see the flowers in the meadow and deny that they are "blind"; both
would be able to obey the request to go fetch a red flower; and yet
only one would have experience. The other would be like an automaton.
Consequently, it is sometimes argued, even a materialist cannot be
wholly sure that other existing minds have experience of a qualitative
(whence, "qualia") sort. The problem for the materialist then becomes
not the problem of other minds, but the problem of other qualia. The
latter seems almost as severe an affront to common sense as the
former. (For an interesting related discussion, see Churchland on
eliminative materialism, 1988, pp. 43-49.)
9. Criticisms of the Mind as a Thinking Thing

We earlier observed that some philosophers, such as Hume, have
objected that supposing that the mind is a thinking thing is not
warranted since all we apprehend of the self by introspection is a
collection of ideas but never the mind that purportedly has these
ideas. All we are therefore left with is a stream of impressions and
ideas but no persisting, substantial self to constitute personal
identity. If there is no substratum of thought, then substance dualism
is false. Kant, too, denied that the mind is a substance. Mind is
simply the unifying factor that is the logical preliminary to
experience.

The idea that the mind is not a thinking thing was revived in the
twentieth century by philosophical behaviorists. According to Gilbert
Ryle in his seminal 1949 work The Concept of Mind, "when we describe
people as exercising qualities of mind, we are not referring to occult
episodes of which their overt acts and utterances are effects; we are
referring to those overt acts and utterances themselves." (p. 25).
Thus, "When a person is described by one or other of the intelligence
epithets such as 'shrewd' or 'silly', 'prudent' or 'imprudent', the
description imputes to him not the knowledge, or ignorance, of this or
that truth, but the ability, or inability, to do certain sorts of
things." (p. 27). For the behaviorist, we say that the clown is clever
because he can fall down deliberately yet make it look like an
accident We say the student is bright because she can tell us the
correct answer to complex, involved equations. Mental events reduce to
bodily events or statements about the body. As Ludwig Wittgenstein
notes in his Blue Book:

It is misleading then to talk of thinking as of a "mental
activity." We may say that thinking is essentially the activity of
operating with signs. This activity is performed by the hand, when we
think by writing; by the mouth and larynx, when we think by speaking;
and if we think by imagining signs or pictures, I can give you no
agent that thinks. If then you say that in such cases the mind thinks,
I would only draw your attention to the fact that you are using a
metaphor. (1958, p. 6)

John Wisdom (1934) explains: "'I believe monkeys detest jaguars' means
'This body is in a state which is liable to result in the group of
reactions which is associated with confident utterance of 'Monkeys
detest jaguars,' namely keeping 'favorite' monkeys from jaguars and in
general acting as if monkeys detested jaguars.'" (p. 56-7).

Philosophical behaviorism as developed by followers of Wittgenstein
was supported in part by the Private Language Argument. Anthony Kenny
(1963) explains:

Any word purporting to be the name of something observable only by
introspection (i.e. a mental event)… would have to acquire its meaning
by a purely private and uncheckable performance . . . If the names of
the emotions acquire their meaning for each of us by a ceremony from
which everyone else is excluded, then none of us can have any idea
what anyone else means by the word. Nor can anyone know what he means
by the word himself; for to know the meaning of a word is to know how
to use it rightly; and where there can be no check on how a man uses a
word there is no room to talk of "right" and "wrong" use (p. 13).

Mentalistic terms do not have meaning by virtue of referring to occult
phenomena, but by virtue of referring to something public in a certain
way. To understand the meaning of words like "mind," "idea,"
"thought," "love," "fear," "belief," "dream," and so forth, we must
attend to how these words are actually learned in the first place.
When we do this, the behaviorist is confident that the mind will be
demystified.

Although philosophical behaviorism has fallen out of fashion, its
recommendations to attend to the importance of the body and language
in attempting to understand the mind have remained enduring
contributions. Although dualism faces serious challenges, we have seen
that many of these difficulties can be identified in its philosophical
rivals in slightly different forms.
10. References and Further Reading

* Aristotle, Categories.
* Armstrong, D. M.: A Materialist Theory of the Mind (Routledge
and Kegan Paul, London 1968) Chapter Two.
* Baker, Gordon and Morris, Katherine J. Descartes' Dualism
(Routledge, London 1996).
* Block, Ned, Owen Flanagan, and Gueven Guezeldere eds. The Nature
of Consciousness: Philosophical Debates (MIT Press, Cambridge 1997).
* Brentano, Franz: Psychology from an Empirical Standpoint trans.
A. Rancurello, D. Terrell, and L. McAlister (Routledge and Kegan Paul,
London 1874/1973).
* Broad, C. D. Mind and Its Place in Nature (Routledge and Kegan
Paul, London 1962).
* Campbell, Keith: Body and Mind (Anchor Books, Doubleday & Co.,
Garden City NJ 1970).
* Chalmers, David J.: The Conscious Mind: In Search of a
Fundamental Theory (Oxford University Press, Oxford 1996).
* Churchland, Paul: Matter and Consciousness, Revised Edition (MIT
Press, Cambridge MA 1988).
* Davidson, Donald: "Actions, Reasons and Causes" The Journal of
Philosophy 60 (1963) pp. 685- 700, reprinted in The Philosophy of
Action, Alan White, ed. (Oxford University Press, Oxford 1973).
* Descartes, Rene: Discourse on Method and Meditations on First
Philosophy, Donald A. Cress trans. (Hackett Publishing Co.,
Indianapolis 1980).
* Descartes, Rene: Descartes' Philosophical Writings, selected and
translated by Norman Kemp Smith (Macmillan, London 1952).
* Descartes, Rene: The Philosophical Works of Descartes, vol.2,
Elizabeth S. Haldane, trans. (Cambridge University Press, 1912).
* Dicker, Georges: Descartes: An Analytical and Historical
Introduction (Oxford University Press, Oxford 1993).
* Ducasse, C. J.: "In Defense of Dualism" in Dimensions of Mind,
Sydney Hook, ed. (Macmillan, NY 1961).
* Garber, Daniel: Descartes Embodied: Reading Cartesian Philosophy
through Cartesian Science (Cambridge University Press, Cambridge
2001).
* Harman, Gilbert: Thought (Princeton University Press, Princeton 1973).
* Hart, William D. "Dualism" in A Companion to the Philosophy of
Mind, Samuel Guttenplan, ed. (Basil Blackwell, Oxford 1994) pp.
265-269.
* Horgan, Terence: "Supervenient Qualia" Philosophical Review 96
(1987) pp. 491-520.
* Hume, David: An Enquiry Concerning Human Understanding (Hackett
Publishing, Indianapolis 1977).
* Joad, C. E. M.: How Our Minds Work (Philosophical Library, 1947).
* Kant, Immanuel: Critique of Pure Reason, Norman Kemp Smith,
trans. (Macmillan, London 1963).
* Kenny, Anthony: Action, Emotion and the Will (Routledge & Kegan
Paul, London 1963).
* Kim, Jaegwon: Philosophy of Mind (Westview Press, Boulder 1996).
* Kripke, Saul: Naming and Necessity (Harvard University Press,
Cambridge 1980).
* Locke, John: Essay Concerning Human Understanding vol. 1,
collated and annotated by Alexander Fraser (Dover Publications, NY
1959).
* Lycan, William: "Philosophy of Mind" in The Blackwell companion
to Philosophy, Nicholas Bunnin and E. P. Tsui-James eds. (Blackwell
Publishers, Oxford 1996).
* Madell, G. The Identity of the Self (Edinburgh University Press, 1983).
* Malcolm, Norman: "Knowledge of Other Minds" in The Philosophy of
Mind, V. C. Chappell, ed. (Prentice-Hall , Englewood Cliffs 1962).
* McLaughlin, Brian P.: "Epiphenomenalism" in A Companion to the
Philosophy of Mind, Samuel Guttenplan, ed. (Blackwell, Oxford 1994).
* Mill, J. S. : An Examination of Sir William Hamilton's
Philosophy, 6th ed. (Longman's, London 1889).
* Nagel, Thomas: "Brain Bisection and the Unity of Consciousness"
in Jonathan Glover, ed. The Philosophy of Mind (Oxford University
Press, Oxford 1976).
* Nagel, Thomas: The View From Nowhere (Oxford University Press,
Oxford 1986).
* Nagel, Thomas: "What Is It Like to Be a Bat?" Philosophical
Review 83 (1974) 435-450.
* Plato: Meno.
* Plato: Phaedo.
* Rey, Georges: Contemporary Philosophy of Mind (Blackwell
Publishers, Cambridge 1997).
* Rorty, Richard: Philosophy and the Mirror of Nature (Princeton
University Press, Princeton NJ 1979).
* Rorty, Richard: "Mind-Body Identity, Privacy and Categories" in
The Mind/Brain Identity Theory, C. V. Borst ed. (Macmillan, London
1970).
* Ryle, Gilbert: The Concept of Mind, (University Paperbacks,
Barnes & Noble, NY 1949).
* Shoemaker, Sydney: Self-Knowledge and Self-Identity (Cornell
University Press, Ithaca 1963).
* Taylor, Richard: Metaphysics, 3rd edition (Prentice Hall,
Englewood Cliffs 1983).
* Tye, Michael: "The Subjective Qualities of Experience" Mind 95
(Jan. 1986) pp. 1-17.
* Williams, Bernard: "Freedom and the Will" in Freedom and the
Will, D. F. Pears, ed. (Macmillan, London 1966).
* Wisdom, John: Problems of Mind and Matter, (Cambridge University
Press, 1934).
* Wittgenstein, Ludwig: The Blue and Brown Books (Harper & Row, NY 1958).