ArticlePDF Available

Abstract

Jeff McMahan has recently developed the embodied mind theory of identity in place of the other standing theories, which he examines and consequently rejects. This paper examines the performance of his theory on cases of commissurotomy or the split-brain syndrome. Available experimental data concerning these cases seem to suggest that a single mind can divide into two independent streams in ways that are incompatible with our intuitive notion of mind. This phenomenon poses unique problems for McMahan's theory that we are essentially minds. I attempt to use his considered response to these cases as a weapon against his own embodied mind theory by highlighting some of the tensions in McMahan's response. In particular, I argue that in reaching his conclusion McMahan admits to something quite contrary to the very spirit of his own theory and that it is a powerful point in its support that one of the theories McMahan rejects can deal very well with these cases.
This article was downloaded by: [UNIVERSITY OF KWAZULU-NATAL]
On: 06 February 2014, At: 23:06
Publisher: Routledge
Informa Ltd Registered in England and Wales Registered Number:
1072954 Registered office: Mortimer House, 37-41 Mortimer Street,
London W1T 3JH, UK
Philosophical Papers
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/rppa20
Courting the Enemy:
McMahan on the Unity of
Mind
Oritsegbubemi Anthony Oyowe a
a University of KwaZulu-Natal
Published online: 20 Feb 2013.
To cite this article: Oritsegbubemi Anthony Oyowe (2013) Courting the Enemy:
McMahan on the Unity of Mind, Philosophical Papers, 42:1, 79-105, DOI:
10.1080/05568641.2013.774724
To link to this article: http://dx.doi.org/10.1080/05568641.2013.774724
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all
the information (the “Content”) contained in the publications on our
platform. However, Taylor & Francis, our agents, and our licensors
make no representations or warranties whatsoever as to the accuracy,
completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of
the authors, and are not the views of or endorsed by Taylor & Francis.
The accuracy of the Content should not be relied upon and should be
independently verified with primary sources of information. Taylor and
Francis shall not be liable for any losses, actions, claims, proceedings,
demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in
relation to or arising out of the use of the Content.
This article may be used for research, teaching, and private study
purposes. Any substantial or systematic reproduction, redistribution,
reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access
and use can be found at http://www.tandfonline.com/page/terms-and-
conditions
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Philosophical Papers
Vol. 42, No. 1 (March 2013): 79-105
ISSN 0556-8641 print/ISSN 1996-8523 online
© 2013 The Editorial Board, Philosophical Papers
DOI: 10.1080/05568641.2013.774724
http://www.tandfonline.com
Courting the Enemy: McMahan on the Unity of
Mind
Oritsegbubemi Anthony Oyowe
Abstract: Jeff McMahan has recently developed the embodied mind theory of identity in
place of the other standing theories, which he examines and consequently rejects. This
paper examines the performance of his theory on cases of commissurotomy or the split-
brain syndrome. Available experimental data concerning these cases seem to suggest that a
single mind can divide into two independent streams in ways that are incompatible with
our intuitive notion of mind. This phenomenon poses unique problems for McMahan’s
theory that we are essentially minds. I attempt to use his considered response to these cases
as a weapon against his own embodied mind theory by highlighting some of the tensions in
McMahan’s response. In particular, I argue that in reaching his conclusion McMahan
admits to something quite contrary to the very spirit of his own theory and that it is a
powerful point in its support that one of the theories McMahan rejects can deal very well
with these cases.
1. Introduction
Jeff’s McMahan’s Ethics of Killing: Problems at the Margins of life is
without a doubt an important contribution to the debate on personal
identity. Its central aim is to provide answers to practical questions,
particular those that emerge at the beginning and ending of life, by
first resolving some metaphysical issues, including especially questions
about the identity of beings at the margins of life and whose status
remain unclear (e.g., fetuses, PVS patients). A great deal of attention
has been given to his answers to those practical questions.1 However, it
is his view on personal identity that interests me here. While
McMahan’s book is remarkable for its in-depth survey of the debate on
personal identity, including a thorough analysis and rejection of the
standing theories, it seems to me that its main contribution to the
1 See Hanser (2005); Perrson & Savulescu (2005); Wasserman (2005) and McKerlie (2005).
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
80 Oritsegbubemi Anthony Oyowe
literature is its defence of the view that we are essentially minds and
that our identity over time is a matter of the continuity of a functioning
brain capable of supporting a mind. He puts forward that view as an
alternative to the psychological view, which he probes and subsequently
rejects. Although I briefly discuss one of McMahan’s objections to the
psychological continuity theory of personal identity, it is not my
intention to respond to those objections in this paper. Ultimately, I
intend to assess the performance of McMahan’s embodied mind view
on certain phenomena that challenge the unity of the mind––in
particular, commissurotomy or the split-brain syndrome.
Available experimental data related to commissurotomy seem to
suggest that a single mind can divide into two independent streams in
ways that are incompatible with our intuitive notion of a mind. This
phenomenon poses problems to the view that we are essentially minds by
casting doubts on the possibility of individuating minds. McMahan
engages in a brief discussion of the puzzle with a view to resolving some
of the tensions that arise for his view concerning the individuation of
minds. The core of his considered response to the puzzle requires us to
give up our intuitive identification of same mind with same
consciousness. I examine his case and argue that dispensing with this
notion of mind is unwarranted. I further argue that his proposed
solution is fraught with tensions and ultimately involves him admitting
something quite contrary to the very spirit of his own theory. More aptly,
in urging the unity of the mind despite the apparent divided
consciousness of commissurotomy patients, McMahan appeals to the
integration of the distinctive features of mental life, which he explicitly
denies any importance in his theory of personal identity. In the end, I do
not believe McMahan makes a compelling case for the unity of mind
based on his embodied mind view. His considered response to the
puzzle, however, generates important new insights on how the
psychological continuity view of identity might respond to the puzzle.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 81
2. The Standard View
In recent years, the dominant view in the debate on personal identity is
the view according to which identity is a matter of psychological
continuity between persons existing at different times. Supposing X
and Y denote persons and t time, then this is the view that ‘X at t1 is
the same person as Y at t2 if and only if Y is uniquely psychologically
continuous with X’ (Shoemaker 2009: 61). The usual clarifications to
the criterion involve what proponents of the view take psychological
continuity and the condition of uniqueness to be. Parfit defines the
former in terms of psychological connectedness (e.g., the relation of
memory to an experience, the persistence of a belief, desire, character
traits etc.). On his view, there is psychological continuity when there
are ‘overlapping chains of strong connectedness’ and since what counts
as strong psychological connectedness is profoundly vague, he claims
that the connections are enough if there are ‘over any day, at least half
the number of direct connections that hold, over every day, in the lives
of nearly every actual person’ (Parfit 1984: 206). Likewise, the
condition of uniqueness, the requirement that there is a sole inheritor
of one’s psychology, is crucial given considerations that psychological
continuity could take a branching form as in Parfit’s much debated My
Division scenario2. The uniqueness clause ensures that there is no other
person Z who bears a similar relation to X as Y. As such, the
uniqueness clause ensures that the criterion captures the logic of
identity3.
2 For details of this thought experiment and its implication for the debate see Parfit
(1984).
3The logic of identity here referred to is the principle of transitivity which implies that if X
is identical to Y and to Z, then Y and Z must be identical. In the case of branching
psychological continuity, two distinct individuals Y and Z emerge from the original one X
but they are clearly not identical and so that principle is not captured. The uniqueness
clause makes possible the one-on-one relation crucial to identity. However, it is instructive
to note that when faced with a scenario in which two individuals are psychologically
continuous with an original one, proponents of the psychological view like Parfit insist that
identity is not what matters in survival. McMahan endorses this view and it forms the basis
of much of the arguments in the remainder of the book.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
82 Oritsegbubemi Anthony Oyowe
There are good reasons why the psychological view is the standard
one. Its main appeal is one that all versions of the psychological view
retain namely, that it accounts well for rational anticipation and self-
concern. Suppose psychological continuity is non-branching, the view
implies that I can rationally anticipate the future experiences of or be
egoistically concerned for the well-being of the individual that inherits
the distinctive features of my psychology (e.g., beliefs). Conversely, I
cannot rationally anticipate the experiences of or be especially
concerned for someone who is not psychologically related to me in the
relevant way. Further, the view is compatible with our ordinary criterion
of self-identification: I am aware that I am the same person that began
typing this essay yesterday not by observing my body but, as Shoemaker
puts it, by ‘simple introspection… consisting in memories, intentions-to-
be-fulfilled, persistence of beliefs/desires/goals, and similarity of
character’ (2009: 65). Despite these attractions, the psychological view
seems to be troubled by a host of other problems.
One such problem concerns its commitment to us being essentially
persons. According to McMahan, the conventional use of the term in the
literature suggests a being with ‘a rich and complex mental life, a mental
life of a high order of sophistication’ (McMahan 2002: 45; see also Parfit
1984: 202). Since infants lack this complexity, we are led to the
seemingly ridiculous conclusion that we, who are now persons, were
never infants. What is at issue then is the assumption that we are
essentially persons; we begin and cease to exist as persons. McMahan
takes the charge further. Since on the psychological view we are
mistaken to think that we, who are now persons, were once infants, and
since a conscious subject precedes the existence of a person (as defined
above), psychological theorists must posit the existence of pre-persons, ‘a
subpersonal subject of consciousness…’ (Or post-persons in end of life
cases as in Alzheimer’s patients when mental life gradually erodes and
psychological connections hold to a much lesser degree incompatible
with what obtains in normal adult persons). McMahan writes, ‘There was,
in short, a conscious being present both immediately before and after
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 83
the birth of one’s organism––a being whose mental life was in some ways
continuous with one’s own… But the assumption that this being was
actually oneself is, of course, mistaken if the Psychological Account is
right… Who, or what, was this conscious being?’ (2002: 46). Since it
appears psychological theorists must posit the existence of more new
entities, pre- and post- persons, his objection is that the theory offends
against parsimony; the view that the plausibility of a theory is diminished
the more new entities it postulates.
McMahan believes that any attempt to revise the standard view will
prove to be unsuccessful.4 It seems reasonable then to explore other
alternatives. Thus, McMahan proposes the embodied mind view
according to which we are essentially minds and the criterion of
identity is the ‘continued existence and functioning, in non-branching
form, of enough of the same brain to be capable of generating
consciousness or mental activity’ (2002: 68).5 Unlike the psychological
view, which stresses the continuity of one’s psychological life, the
embodied mind view stresses ‘the continuity of psychological capacities
–in particular, the capacity for consciousness’ (ibid.). The distinction
between these two kinds of continuities will be crucial in subsequent
section when I closely examine McMahan’s response to the split-brain
syndrome. In the meantime, it is instructive to note that it is central to
his view that there is physical continuity and that he takes the notion of
same consciousness to be equivalent to same mind. Importantly, the
4 McMahan explores possible revisions of the psychological view including the proposal
that psychological continuity be construed in terms of broad psychological connections
(i.e., connections that hold to any degree of strength). While this proposal would resolve
the problem of pre- and post- persons, it will be unsuccessful with regards to the isolated
subject charge (see McMahan 2002: 64–65). In general, I find McMahan’s attack against
the psychological view contentious but will not discuss my misgivings here.
5 The theory actually divides into two–the theories of identity and egoistic concern. The
reason for this is that McMahan believes that identity and egoistic concern for the future
can be prised apart. However since McMahan prefers an account that seeks to establish
congruence between the theories of identity and egoistic concern, he proposes that
physical and functional continuity of enough of the same brain capable of generating
consciousness is also both necessary and sufficient for egoistic concern.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
84 Oritsegbubemi Anthony Oyowe
embodied mind view has some merits of its own. In general, it deals
well with some of the problems associated with the psychological view.
It is resistant to the newborn problem highlighted earlier. Since it
maintains that we begin to exist when the brain develops the capacity
to support a mind, it follows that we begin to exist sometime before we
were born. The emphasis on psychological capacities and physical
continuity, rather than the contents of one’s mental life, allows the
theory to retain the intuition that one continues to exist and is justified
in fearing future pain even after psychological connections from day to
day have ceased to hold.
This view begins to lose initial appeal, however, when we closely
consider its performance on cases of commissurotomy. Since these cases
seem to suggest that a single brain could support two minds at the same
time, it poses unique problem for the embodied mind view which seeks
to individuate minds by reference to the same brain. If the same brain
can support the existence of two distinct minds at the same, then there is
a potentially damaging problem lurking for McMahan’s embodied mind
view, with specific reference to the criterion that is being used to
individuate minds at a time.
3. Commissurotomy: A Tale of Two Minds?
McMahan is not unaware of the potentially damaging problem and the
scenario that engenders the problem is not far-fetched. Cases of
commissurotomy seem to suggest that the same brain could sustain more
than one mind at a time; a scenario that spells imminent doom for the
embodied mind view.6 There is a rich and fascinating literature on the
unity of mind, with particular reference to what actual cases of
commissurotomy imply about that unity. The starting point of
6 Cases of multiple personality disorder also pose similar problems but McMahan prefers
not to comment on these cases as he thinks that there is at yet little understanding of what
happens in these cases, and in particular, little understanding of the neurological basis of
the disorder (2002: 87). Again, I strongly disagree with McMahan’s way of dismissing this
problem but I will let it go for now.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 85
philosophers working in this area has been psychological studies7 done
on commissurotomy patients. Commissurotomy is a surgical operation in
which the corpus callosum, consisting of fibres connecting the two
cerebral hemispheres of the brain, is severed resulting in an apparent
loss of information transfer between the two hemispheres. Following the
operation, these patients behave normally and most observers tend not
to notice anomalies in their personalities. Even so, it is well documented
that they exhibit philosophically puzzling behaviours under certain
experimental conditions. Charles Marks narrates an interesting and
revealing case:
A subject, S, is told to fixate a point on a screen before him. ‘Key ring’ is
flashed on the screen for a tenth of a second, with ‘key’ appearing to the left
of the fixation point and ‘ring’ to the right. Since the time is too brief for eye
movement, the information from the right visual field (‘ring’) is projected
exclusively to the left hemisphere and information from the left visual field
(‘key’) is projected exclusively to the right hemisphere… If S is asked to sort
through an array of items (concealed from sight) with both hands and pick
out what he saw, the right and left hands work independently… In general,
when the response demanded is controlled by the left hemisphere, it
indicates that S was aware of ‘ring’ and unaware of ‘key’; when the response
demanded is controlled by the right hemisphere, it indicates that S was aware
of ‘key’ and unaware of ‘ring’. Someone seems to have seen ‘key’ and
someone seems to have seen ‘ring’ and they seem unaware of each other.8
Quite clearly the ability of the left and right hemispheres to function
independently is crucial in order to fully grasp what happens in these
controlled conditions. The relevant information here is that the right
hemisphere controls movement associated with the left part of the
subject’s body and vice versa. The puzzle then is that there is no single
awareness that someone seems to have seen ‘key’ and someone seems to have seen
‘ring’. Thus it appears that there are therefore two subjects of experience
7 These studies were mostly done in the early 1960s by Neuro-scientist Roger Sperry (see
his 1968) of the California Institute of Technology on patients who had undergone
commissurotomy as a result of suffering from epilepsy. The operation is said to alleviate
the painful seizures these patients undergo (see McMahan 2002: 19; also Parfit 1984).
8 Marks (1981: 4–5).
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
86 Oritsegbubemi Anthony Oyowe
since the mental processes associated with each hemisphere are similar
to that in normal persons, who are taken to be subjects of experience
(Mark 1981: 7). Consequently, it is generally agreed within the literature
that there are two streams of consciousness.
There are five possible interpretations of the experimental data in
the literature.
1. The patients have one fairly normal mind associated with the left
hemisphere, and the responses emanating from the nonverbal
right hemisphere are the responses of an automaton, and are not
produced by conscious mental processes.
2. The patients have only one mind, associated with the left
hemisphere, but there also occur (associated with the right
hemisphere) isolated conscious mental phenomena, not
integrated into a mind at all, though they can perhaps be ascribed
to the organism.
3. The patients have two minds.
4. They have one mind, whose contents derive from both
hemispheres and are rather peculiar and dissociated (i.e., they are
not well integrated as normal minds)
5. They have one normal mind most of the time, while the
hemispheres are functioning in parallel but two minds are elicited
by the experimental situations which yield the interesting results.9
I begin with a brief comment on the first interpretation before
proceeding to state the problem associated with the first two. The
activities of the nonverbal right hemisphere are taken to be responses of
an automaton and thus not conscious. The reason is that the split-brain
subject verbally denies any awareness of the activities of the right
hemisphere. It is precisely for this reason that the right hemisphere is
denied a mind. But, as Nagel argues, that sort of reasoning begs the
9 Nagel (1971: 402–403).
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 87
question as the capacity for speech is controlled entirely by the left
hemisphere. He also adds that taking verbalizability as a necessary
condition of consciousness cannot be justified in principle (Nagel 1971:
403). In any case, the problem with the first two interpretations is that
their denial of a mind to the right hemisphere is arbitrary. In the event
that the left hemisphere ceases to function completely, the independent
functioning of the right hemisphere will suffice to ascribe a mind to the
split-brain patient and vice versa. This fact rules out in advance the
suggestion that the activities associated with either of the hemispheres is
not that of a mind. The fifth interpretation is independently implausible
as there are no physiological changes induced in the patients during the
experimentation that accounts for them shuttling between one and two
minds. The idea of a mind splitting under experimental conditions and
reconvening afterwards seems to me to be absurd. Thus the third and
fourth responses to the split-brain puzzle remain the plausible options
and will be central to the rest of the discussion.
The third interpretation of the experimental data is that the patients
have two minds. However, because of the behavioural integration in
these patients (they behave like every normal person), what is needed is
an explanation of the integrated function of both minds outside
experimental conditions––since it appears that outside these conditions
there is only one mind just as it is with non-commissurotomy patients.
So, if no explanation of the obvious integration of the alleged two minds
of split-brain patients in everyday life is forthcoming, we may want to
reject option three above. I shall be arguing that not only is such
explanation on hand, but also that this response fares better than the
other contenders.
For present purposes, the fourth interpretation requires detailed
consideration as McMahan’s conclusion on the split-brain problem
corresponds to it. The claim here is that commissurotomy patients have
one mind, whose content derive from both hemispheres. McMahan claims
that a single mind can encompass two centres of consciousness. On his
view, two or more fields of consciousness are held to constitute a single
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
88 Oritsegbubemi Anthony Oyowe
mind rather than a collection of minds, not merely because they are
supported by a single brain, but because there is sufficient integration
among the various mental states generated in the different fields. The
plausibility of recognizing two minds increases as the degree of separation
between them increases (McMahan 2002: 87–88). Here, McMahan reasons
on the basis of observations that there is coordination in the behaviour of
split-brain patients in everyday life, which ostensibly indicates the presence
of a single mind. Thus, he concedes that it will be plausible to claim that
the patients have two minds both supported by a single brain, if and only
if it was observed that their behaviours were consistently incongruous. One
obvious problem with this response is that in affirming a single mind it
faces the difficulty of making sense of the fact that under experimental
conditions there is a clear disintegration that is inconsistent with a single
mind. It appears that a single mind can attend to different tasks at the
same time with either centre of consciousness lacking access to the other.
As Nagel writes, ‘…in these patients there appear to be things happening
simultaneously which cannot fit into a single mind: simultaneous attention
to two incompatible tasks, for example, without interaction between
[them]’ (1971: 407, emphasis as in original).
The difficulty here is revealed more cogently when we consider that
intuitively our concept of mind is characterised by the synchronic unity
of consciousness; that is, the various experiences and conscious states of
a person at a given time are held to be accessible in one unified
consciousness. However, McMahan wants us to dispense with that
concept of mind. He appeals to ordinary cases in which the mind can
attend concurrently to two tasks viz. driving a car while being distracted
and later recalling the image of a billboard of which one was not
conscious at the time of seeing seem to corroborate a concept of mind
that spans multiple centres.10
I should point out straightaway that I suspect that there are grounds
for doubting that these ordinary cases are relevantly similar to the
10 McMahan employed this example in his comments on this paper.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 89
experience of split-brain patients. Indeed, our experience is such that at
any given moment there may be certain concerns at the forefront of
consciousness in the sense of being dominant while others are forced to
the fringes precisely because they are less important. But this is hardly
suggestive of mental disintegration or distinct centres of consciousness––
at least in the sense implied in cases of commissurotomy patients. In the
ordinary cases, it appears that the issue is more about which element of
consciousness is taking centre stage at a given moment and which ones
are less important in the sense that they have been pushed as it were to
the fringes. However in commissurotomy cases, the real puzzle comes in
there being conscious states to which other conscious states have no
access. Moreover, in the split-brain cases what we observe is that the
respective centres of consciousness act independently and can carry out
incompatible tasks at the same time. Ordinary cases of distraction (in the
sense of diverting one’s attention to dominant concerns) need not be
seen as cases of disintegration, which is precisely what is at issue in split-
brain patients. At the centre of the conceptual puzzle emerging from
commissurotomy cases lies the personal and mental ascription of
psychological states to the left and right hemispheres, something which
is lacking in our ordinary cases of distraction.
4. Critical Comments on McMahan’s Response
In reaching his conclusions on the split-brain conundrum, McMahan
glosses over a number of salient issues. In what follows, I draw attention to
three that I think are worth mentioning. I begin by reiterating that in line
with observations that split-brain patients behave normally in everyday
life, McMahan’s claim is that these patients retain a single mind. He
argues that if the reverse were true, then commissurotomy would involve
split-brain patients having two minds. But as this is not the case, McMahan
claims that the disunity in mental life exhibited by split-brain patients is
attributed to their having two independent centres of consciousness. His
solution is that split-brain patients have two centres of consciousness (as
observed under experimental conditions) but one mind (as observed in
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
90 Oritsegbubemi Anthony Oyowe
their coordinated behaviour). For the solution to work, he proposes that
we give up our intuitive identification of ‘same mind’ with ‘same
consciousness’ as the puzzle challenges this intuitive identification (2002:
87). This would allow for an understanding of mind that is compatible
with two (or perhaps, more) streams or centres of consciousness. The
proposed solution however turns out to be a major leap.
Contrary to McMahan’s claim, the experimental data doesn’t
necessarily challenge our intuitive identification of same mind with same
consciousness, but rather the assumption that we are essentially minds.
The independent functioning of each hemisphere seems to point to the
presence of two minds supported by two hemispheres. Supposing that one
of the hemispheres ceases to function during the operation; we certainly
cannot deny the surviving single-hemisphere patient a mind. So, it is hard
to see why we should when they each seem to function independently. It
appears that there is nothing in the experimental data of split-brain
patients that compels us to deny offhand the presence of two minds.
I believe that what we have here is a dilemma: a choice between
seeing these cases as involving split-brain patients exhibiting either two
minds (as I shall be arguing) or a single mind (as McMahan suggests).
On the one hand, we can claim that the two hemispheres support two
minds, although there is still one person present post-commissurotomy.
In doing so, we retain the intuitive identification of same mind with
same consciousness. Clearly, the two-mind reading of commissurotomy is
damaging to McMahan’s thesis that we are essentially minds, especially
with regards to the possibility of individuating minds. Admittedly, this
proposal seems counterintuitive; it is hard to believe that a single person
can have two minds. Even so, this is no more a problem for this option
than it is for the alternative one put forward by McMahan. On this
alternative solution to the split-brain syndrome, the claim is that the two
hemispheres of split-brain patients support two centres of consciousness
but nevertheless a single mind. This requires giving up that intuition by
which we identify same mind with same consciousness, a result that is
equally counterintuitive, since our intuitive notion of mind is not
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 91
compatible with two or more separate streams of consciousness. Not
surprisingly, McMahan goes with the option that saves his theory.
But why should we accept the latter proposal and not the former?
That is, it is not clear to me why we should accept a two-consciousness
explanation rather than a two-mind one.11 What do we stand to gain in
doing this, other than merely rescuing the embodied mind theory? Two
possible reasons present themselves, but they both fail to persuade. First,
it appears that the two-consciousness reading of the split-brain puzzle
accounts well for the obvious behavioural integration in commissurotomy
patients. This, it seems, is the strongest motivation for McMahan’s two-
consciousness solution to the split-brain puzzle. Throughout his brief
discussion of the puzzle, McMahan repeatedly reasons from the
observation of behavioural integration in these patients to the fact that
there is a single mind. In his words, ‘[I]f events of this sort [i.e.,
incongruent mental states and behavioural responses from each
hemisphere] had begun to occur consistently, on a daily basis, we would,
I think, have accepted that there were two minds present, both
supported by the operations of a single brain’ (McMahan 2002: 88).
Positing two centres of consciousness allows him to account for the
disunity in the mental life of commissurotomy patients as observed
under experimental conditions, while their coordinated behaviour
outside those conditions is explained in terms of a single mind.
Even so, I think there is a problem lurking here for McMahan. For
these patients to function normally as they do in everyday life there has
to be a sufficiently high degree of integration of both centres of
consciousness, both in terms of capacities and contents. But because they
exhibit roughly the same degree of behavioural integration as people
with normal brains, there is good reason to think that the degree of
integration and complementarity in split brain patients would be far
11 This first option (two-consciousness) should be read more accurately as one-mind, two-
centers-of-consciousness, while the second (two-minds) should be read as one-person, two-
minds. But I shall be using the less cumbersome two-consciousness and two-minds
respectively to mean just these.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
92 Oritsegbubemi Anthony Oyowe
beyond mere coordination of distinct centres of consciousness. If the
centres of consciousness are integrated to such a degree, it would appear
that there are not two distinct centres, but one as we would imagine is
the case in people with normal brains. Put more aptly, if the degree of
integration is sufficiently high to permit the recognition of a single
mind, is it not then plausible to insist that the alleged distinct centres of
consciousness collapse into one? But McMahan would not have one
centre of consciousness if he is to account for the apparent disintegration
in mental life of split-brain patients. The point I wish to make here is
that the overarching one mind cannot sufficiently explain the
integration in the way McMahan has suggested. For if the two centres of
consciousness were integrated to a sufficiently high degree to constitute
a single mind, then there seem to be no reason to think that they are
indeed two centres. But if there are not two centres of consciousness,
there is no way of explaining disintegration in the mental life of
commissurotomy patients.
Moreover, even if we grant that the two-consciousness reading can
account well for the behavioural integration in commissurotomy
patients, I am not convinced that one who instead agrees with the two-
mind thesis cannot equally account for this. It seems to me that one can
claim that although these patients have two minds, their coordinated
behaviour is a function of a sufficiently high degree of integration
among the distinctive features of mental life. And it is precisely such
integration, rather than the having of mind(s), that matters in their
being persons in the sense of being unified subjects. And further, it is
when there is a lack of such unity that we then have a split in persons.
Positing two minds ensures that one can account for the disunity in the
mental life of the patients under controlled conditions, while their
coordinated behaviour in everyday life is explained in terms of the
degree of integration (high enough for single person-hood) among the
contents of the distinct minds. The point is that consideration that the
two-consciousness view can account for the behavioural integration of
split-brain patients is not by itself a point of support for it seems that the
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 93
two-mind view can as well. Thus, it appears that this reason is not strong
enough to motivate the two-consciousness rather than the two-mind
thesis.
Second, it may be claimed that the two-consciousness explanation is
preferable on the grounds that it permits a characterization of mind
that, as McMahan claims, can tolerate a certain degree of disintegration
compatible with what is observed under experimental conditions (2002:
88). If this is so, and we accept that in normal cases the mind can
tolerate a certain degree of disintegration, then there may be good
reasons for preferring the two-consciousness view, which on the face of it
seem to account well for this.
However, this way of setting up the issue seems to me to occasion
question begging––that is, it seems to assume the embodied mind theory
to be true. I think that what is in need of explanation is not how our
notion of mind can tolerate disintegration but rather, how to explain the
disintegration in the mental life of split-brain patients. This explanation
can be made in terms of a single mind or two. What is crucial is that we
set out the issue in a manner that leaves open the question of whether we
are essentially minds or not––or more aptly, whether commissurotomy
patients have one, two or more minds. If we assume beforehand that we
are essentially minds (that is, beings with the capacity for consciousness),
there is the tendency to explain the disintegration in terms of multiple
centres of consciousness, thereby retaining the intuition that after
commissurotomy there remains a single mind in spite of the
experimental data. This is in part due to the intuition that the mental
life of split-brain patients is predominantly unified. But if we reject that
assumption, we do not need to claim that there is a single mind post-
commissurotomy. We could claim that commissurotomy patients exhibit
behaviours consistent with the working of two minds under controlled
conditions, although these minds coordinate together to a sufficiently
high degree in normal situations. This, of course, preserves the intuition
that there is a unified subject post-commissurotomy, without claiming
that there is therefore a single mind.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
94 Oritsegbubemi Anthony Oyowe
If I am right that the important concern should be accounting for
mental disunity of commissurotomy patients, rather than providing a
concept of mind that can tolerate a certain degree of fragmentation, then
holding on to the intuitive notion of mind proponents of the two-mind
view possess the conceptual resources to give such an account. All they
need claim is that the behavioural disintegration in split-brain patients is
due to them having two minds supported by each hemisphere; their
independent workings become apparent under controlled conditions.
However, outside those conditions when the contents of both minds are
sufficiently integrated, as observed in everyday life, we can plausibly
recognize the presence of a single person.12 Note that what matters in
their being persons is the high degree of integration among the contents
of mental life; the higher the degree of integration among mental states,
the less significant is the fact that there are two minds. To reiterate the
point, there is no clear and independent reason for preferring a two-
consciousness rather than a two-mind reading unless one assumes offhand
that we are essentially minds. But to do so is to beg the question against
the psychological view and other standing theories of identity.
A further worry concerns how McMahan’s attempt to resolve the split-
brain conundrum both obscures and betrays the fact that the brain no
longer plays the crucial role it previously did in individuating minds. I
will try to justify this claim. In setting out his solution, McMahan
presents an imaginary case in which commissurotomy patients
consistently behaved in anomalous ways. He writes, ‘suppose that as time
passed, their left hands [controlled by the right hemisphere] began to
write out messages expressing desires, feelings, and beliefs contrary to
those they articulated verbally’ (presumably by the left hemisphere which
controls speech). If this were the case, McMahan admits that we would be
right to recognize the presence of two minds, in spite of there being a
12 Note that the arguments here relies heavily on the distinction between ‘minds’ and
‘persons’, both picking out sortal substances. McMahan takes mind to be the bare capacity for
consciousness and in the literature on personal identity, persons refer to a being with a
sufficiently high level of mental competencies (see McMahan 2002: 45 and Parfit 1984: 202).
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 95
single brain. But as these patients do not behave in these ways, at least
not consistently, we must ascribe only a single mind to each. At this
point, what criterion is being used to individuate minds? It is clearly not
the notion of a single brain, since in principle a single brain could
support the existence of two distinct minds––a possibility with which
McMahan agrees. McMahan throws into the mix a new criterion: the
idea that the distinct centres of consciousness brought about by the
severing of the cortices linking both hemispheres constitute a single
mind not just because mind is supported ‘by one brain or two, but also
on the degree of integration among the various mental events.’
(McMahan 2002: 88). He adds that should each centre of consciousness
develop ‘a distinctive mental life of its own, it becomes increasingly
plausible to recognize the existence of more than one mind’ (ibid.).
Although this may appear to point to two criteria for individuating
minds, it actually initiates a gradual departure from his original view that
individuates a mind by reference to the brain (2002: 67). Introducing a
second individuating criterion is, it seems to me, an attempt to shift
attention away from the brain to the contents of mental life, which now
takes centre stage. But which of these two is really doing the work for
individuation? A closer analysis reveals that it is not the brain; it is in fact
the newly introduced criterion. The significance of the notion of the
same brain in McMahan’s embodied mind theory is that it provides a
substructure in which minds are generated and sustained over time.
Ordinarily, we take this to mean that there is some sort of mind-brain
dependency relation. However, McMahan’s agnosticism about that
relation opens room for doubts about the nature of that relation,
especially now that we have to think of it as a three-place relation (i.e.,
mind-consciousness-brain dependency relation).13
What should we make of this mind-consciousness-brain dependency
relation and what criterion of individuating minds is being used here? It
13 For a discussion of some of the main problems confronting the mind/brain dependency
relation as they affect McMahan’s embodied mind view see De Grazia 2003. It appears to
me that the problem is even more glaring given the three-place dependence relation.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
96 Oritsegbubemi Anthony Oyowe
seems that the mind is not directly dependent on the brain even if centres
of consciousness are. Split-brain patients have their brains, previously
supporting single minds, bisected and this is no minor change in the
anatomy of the brain. If McMahan is right, this surgical process does not
divide the mind––at least not directly, but rather divides what was a
single centre of consciousness. It seems then that McMahan has to
conceive of mind as that which underlies a divided consciousness
resulting from major changes in the anatomy of a brain and is picked
out by its role in behavioural integration. The definition seems fair. After
all, it is his view that the unity of mind is preserved following brain
bisection. The mind, whatever it is, must underlie both the severing of
the corpus callosum and the resulting centres of consciousness. But
recognizing the presence of a mind is a matter of recognizing not just
facts about the brain, but that there is sufficient integration among the
various events of mental life (2002: 88). And if this is true, why is the
physical substrate of mind relevant at all?
As it turns out, not only is McMahan asking us to believe that the act
of surgically bisecting the corpus callosum in one’s brain has the effect
of dividing consciousness rather than mind, he is also asking us to
believe that on his view the integration of mental events is necessary
for the unity of mind. But all along we have been led to believe that the
mind is the capacity for consciousness; that is, for us who are essentially
minds––beings with the capacity for consciousness––it is the having of
psychological capacities rather than contents that is necessary for identity
(McMahan 2002: 68-69). It is precisely this idea that informs his charge
that the psychological view is found wanting in not being able to
account for the conscious subject that continues to exist when all of its
distinctive features or contents, and therefore the connections among
them, have been eroded (2002: 65). But now, the notion of a mind
seems to require integration of the contents of one’s psychology of the
sort psychological theorists rely heavily on and which, on McMahan’s
view, is not necessary for identity. However as the necessary features of
our continued existence depend on what we essentially are and since
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 97
on McMahan’s view we are essentially minds––beings with the capacity
for consciousness––it is the continuity of that capacity that matters for
identity and should for individuation, not facts about the contents or
integration among the events of mental life. And although McMahan
claims that the continuity of the distinctive features of mental life is not
among the relation of identity over time (2002: 69, 79), he sees no
trouble introducing it as necessary for individuating minds at a time.
As well, it is vital to reiterate that McMahan’s appeal to mental
integration as doing the important work for individuating minds is a
radical departure from his expressed view that the continuity of a
brain’s capacity for consciousness is what matters for identity. This view
does not require the contents of mental life. Even so, McMahan urges
the unity of mind by appealing to it. But if it is necessary for a mind’s
being the same mind (rather than two or three other minds) that it
retains continuity of the distinctive features of psychology then it is
hard to see how such distinctive features and their continuity fail to be
a necessary part of what constitutes the identity of a mind in the first
place. In observing that McMahan denies that the distinctive features
of psychology are necessary for identity, yet claims that they matter for
the unity a mind, I call attention to the fact that not only is there a
tension in McMahan’s account but also that he is admitting to
something contrary to the core of his embodied mind theory.14
5. Probable Objections
So far, I have argued that there are no independent reasons for
preferring the two-consciousness response to the split-brain puzzle
rather than the two-mind response; that the two-consciousness response
14 So far, I have argued that there is a tension in McMahan’s account of the unity of minds as
it permits contents to play a central role in the individuation of minds, but not in identity over
time. However, it may be argued that there is a difference between conditions of diachronic
identity (persistence or identity over time) and synchronic identity (individuation or identity
at a time) and that what McMahan has to say about the former has no direct entailments on
what he has to say about the latter. Nonetheless, I contend that there remains a tension in his
theory if contents play a central role in one and not in the other.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
98 Oritsegbubemi Anthony Oyowe
to the puzzle commits the embodied mind view to a three-place
dependency relation between mind, consciousness and brain15; and that
McMahan’s considered response to the puzzle involves him admitting
something contrary to the spirit of his embodied mind theory. In this
section, I turn attention to a number of considerations that may be
raised against the arguments I have put forward here as they relate to
McMahan’s embodied mind theory, and in particular, his response to
the split-brain puzzle.
First, it appears that throughout I have assumed that
commissurotomy involves bisecting the (whole) brain and it is on the
basis of this assumption that I advance the two-mind reading of the
experimental data. But the operation only affects the corpus callosum
and there is much more to the brain than the corpus callosum. The
entire lower brain is not affected by the operation and it appears it (the
lower brain) may contribute in some important ways in supporting the
capacity for consciousness. Moreover, the hemispheres seem to be able
to communicate through other pathways in spite of the severing of the
cortices linking both hemispheres.16 The point here is that the whole
brain is not bisected and therefore the anatomy of the brain post-
commissurotomy does not support two minds in the way I have
suggested.
Even so, as far as McMahan’s embodied mind theory is concerned it
is not the entire brain that is necessary for synchronic or diachronic
identity. Rather, it is enough of those areas of the brain that contribute
to the capacity for consciousness. That commissurotomy doesn’t affect
certain parts of the brain may just turn out to be a trivial point if those
parts contribute nothing or significantly less towards the capacity for
consciousness. So, while it may be true that commissurotomy does not
divide the whole brain, it seems to divide those areas of the brain that
15 This of course is an added worry seeing that accounting for the dependency relation
between mind and brain alone is already an exertion on McMahan’s embodied mind
theory. See De Grazia 2003 for details of this argument.
16 Kathleen Wilkes also discussed these problems in her book Real People (1988), Ch 5.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 99
support the capacity for consciousness. Besides, there is good reason to
believe that the brainstem contributes considerably less towards the
generation and continued support of that capacity as far as we know.
The essential regulatory function of the brainstem is closely aligned to
the nervous system and other bodily processes; it is in the cerebral cortex
of the brain that the capacity for consciousness and the contents of
mental life are realized and sustained. This is evidenced in the fact that
selective damage to the lower brain does not result in impairment of
mental capacities or loss of mental states (e.g., memory: as there are no
neurological correlates of the contents of consciousness in the brainstem)
in the same way selective damage to the cerebral cortex does.17
If the brainstem’s contribution to the capacity for consciousness is
negligible (here, we assume with McMahan that the mind is the capacity
for consciousness) and if commissurotomy divides those regions of the
brain that are essential for realizing that capacity, then the fact that the
whole brain is not divided, or that the brainstem is unaffected by the
operation does not abrogate the intuition that dividing the cortices that
link both hemispheres results in two minds. Similarly, while it is true that
there is communication between the two hemispheres through other
pathways, in spite of the severing of the corpus callosum, it does not
follow that there is therefore a single mind. The tendency of both
hemispheres towards confabulation may in all likelihood be suggestive of
subjective unity, but this is far from clinching the case for the unity of
mind. This is because subjective unity as I have argued may be explained
in terms of the unity of person, that is, a sufficiently high degree of
integration in the contents and distinctive features of the distinct minds
supported by both hemispheres. This view does not abrogate the
intuition that there is subjective unity in commissurotomy patients
insofar as there is a sufficiently high degree among the contents of the
distinct minds. And throughout I have maintained that there are no
17 McMahan has discussed in some depth the minimal contribution of the brain stem in
realizing and sustaining minds. See especially his 2002, pg 21.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
100 Oritsegbubemi Anthony Oyowe
independent reasons for preferring McMahan account of the unity of
mind over the alternative view that there is a single person with two
minds post-commissurotomy.
Another interesting case that may be advanced in defense of
McMahan’s solution to the problem is that his account of a unified mind
is closely tied to the idea of a unified brain. Since commissurotomy
patients have a unified brain they must therefore have a unified mind,
the argument runs. However, if what is meant by unified brain is the
whole brain, then earlier considerations come to bear on this issue as
well. Commissurotomy does not and need not divide the whole brain;
but it seems to divide the important regions, and if we take seriously the
experimental data, then it divides consciousness as well. Thus, it is not
clear in what sense those regions are unified. Further, it is not clear on
McMahan’s account that having a unified brain entails having a unified
mind. He accepts in principle that the operation of a single brain could
sustain two minds (2002: 87–88) and that what makes two distinct
centres of consciousness a single mind rather than two is not just that
there is a unified brain but that there is sufficient ‘degree of integration
among the various mental events.’ (2002: 88).
Relatedly, it may be argued that McMahan provides a variety of
considerations which relate the concept of a mind to that of an organism.
Perhaps the arguments put forward here have overlooked these
considerations and how they may relate the concept of a unified mind to
that of a unified organism. Once again, the inference that wherever we
find a unified organism, there must therefore be a unified mind does not
follow. I believe that McMahan’s commitment to the view that what we are
(in his view, minds) and the organism of which we are a part can be prised
apart, prepares the ground for the possibility that a unified organism may
support the existence of two distinct minds as parts.
Lastly, one of the central claims on which much of the arguments I
have put forward here hinges is the claim that McMahan individuates
minds by the degree of integration among the contents and distinctive
features of mental life. I have argued that if content plays a central role in
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 101
individuation (synchronic identity) and not in identity over time
(diachronic identity), then there is a tension in McMahan’s embodied
mind theory and that this cast doubts on the plausibility of his response
to the split-brain conundrum. However, the terms contents and
distinctive features are not ones that McMahan uses. He says that
whether there is one mind or two depends on the degree of integration
among the various mental events. Admittedly, the terminology is unclear;
and it is possible McMahan rejects contents and distinctive features but
accepts events as playing some role in the identity of minds, in particular
the individuation of minds.
In response, I will make two very brief claims. First, it is doubtful that
McMahan accepts events as playing any role in the identity of minds
seeing that mind is the bare capacity for consciousness, not necessarily
the actualization of that capacity. Second, there seem to be good reason
to think that when McMahan speaks of mental events, he actually means
what I mean by contents/distinctive features of mental life. Thus, in
considering how the case of split-brain patients might have been
different and suggestive of the existence of two distinct minds, he alludes
to a lack of integration in the ‘desires’, ‘feelings’ and ‘beliefs’ (which are
clearly contents/distinctive features of mental life) expressed by the left
and right hemispheres (2002: 87). When he comes to explain why
commissurotomy patients each have a single mind, he relies almost
entirely on the degree of integration among the ‘desires’, ‘feelings’ and
‘beliefs’ in both hemispheres. The point I am making here is that
however one may interpret the term ‘events’, one will have to include
‘desires’, ‘feelings’ and ‘beliefs’, these contents and distinctive features of
mental life as central in the set of items the term picks out. Overall, then,
these objections do not vindicate the embodied mind theory or show that
the arguments I have advanced here ought to be rejected.
6. Concluding Remarks
It is important to highlight that although the embodied mind view
cannot provide the appropriate response to the split-brain puzzle, the
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
102 Oritsegbubemi Anthony Oyowe
psychological continuity theory can. All along, the core of my claims has
been that the response McMahan offers to the puzzle is more suitable to
the psychological view. That is, that a theory of personal identity that
turns on the continuity of the distinctive features of mental life rather
than the continuity of capacities is well suited to account for the
subjective unity of split-brain patients. According to the psychological
continuity theory, identity is a matter of the continuity of beliefs, desires,
etc. To the extent that these features are sufficiently integrated in a split-
brain patient, this view affirms the presence of a single person albeit with
two minds (as corroborated by experimental data), thus retaining the
intuition that a mind is individuated by synchronic unity of
consciousness. On this view, whether or not an individual has one or two
minds becomes less significant to the extent that there is sufficient
degree of integration among contents of mental life. The point I wish to
make here is that not only is this a point of support for the psychological
view of identity, it is also the central insight we gain from McMahan’s
own considered response to the puzzle: the insight that the appropriate
response to the split-brain puzzle supports the psychological theory
rather than the embodied mind view of identity.
I have already admitted that the two-mind-one person response to
the puzzle clearly has a counterintuitive feature; it is hard to believe that
a single person can have two minds. Earlier on, I maintained that this is
not more a problem for the two-mind response than it is for the two-
consciousness response. And indeed this is not a problem in and of itself
seeing that the experimental data from cases of commissurotomy begs
for an explanation that takes seriously the fact of distinct set of conscious
activities occurring in the two hemispheres. That is, that the
hemispheres of split-brain patients work independently and that there is
the problem of inaccessibility between the conscious phenomena in both
hemispheres. Although providing a comprehensive account of minds,
persons etc or an in-depth discussion of what a two-mind response to the
puzzle entails will go beyond the immediate scope of the paper, I wish to
explain why we should see beyond the counterintuitive feature of the
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 103
two-mind response and begin to embrace it as a compelling response to
the split-brain puzzle.
One way of making this response less offensive to the intuition of
ascribing a mind to a single person is by considering puzzle cases of
fission in personal (numerical) identity. As they have been discussed in
the literature, these cases are meant to uncover the implications of our
understanding of personal identity by imagining a situation in which a
single person splits into two distinct persons. This usually involves the
transfer of each half of the upper brain from one body to distinct
decerebrate bodies. What is central in consideration of these cases is that
the resulting persons have the full complement of the distinctive features
of the original person’s mental life.18 There is consensus within the
literature that if a person were to divide in this way, there will be two
distinct persons psychologically related to the original. I think that cases
of fission offer some insight into understanding the split-brain puzzle,
particularly assuaging some of the worries that may arise regarding the
possibility of a single person possessing two minds. Of course, I am not
claiming that cases of commissurotomy and fission are the same. It
would indeed be absurd to do so.
The point I wish to make, however, is that cases of commissurotomy
are in the middle points in a continuum at one end of which we have
single persons with single minds and at the other a complete split as in
fission cases that permits the recognition of two persons.19 Importantly,
as the degree of integration among the contents of mental life decreases
sufficiently, we begin to plausibly recognize the presence of two minds
18 See Wiggins (1967: 52-55) and Parfit (1984: 254-255) for detailed consideration of
fission cases.
19 I wish to state that the view advanced here differs substantially from the one found in
Puccetti (1973, pg 339-355). Puccetti argues that ‘two minds is logically equivalent to two
persons’ and goes a step further claiming that ‘even in the normal, cerebrally intact human
being there must be two persons,’ and commissurotomy only makes this fact obvious. I do
not make these claims and my paper does not address them; my view is that
commissurotomy shows us how it is possible for a single person to have two minds and that
we can only plausibly acknowledge that there are two persons if the separation between the
contents of the mind is sufficiently widened.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
104 Oritsegbubemi Anthony Oyowe
and ultimately two persons. Thus, to the extent that we can tolerate the
possibility that single persons could split into two distinct persons with
two distinct minds, we would be more at home with the idea that
commissurotomized persons have two minds, not sufficiently separated
to permit the recognition of two persons.20
University of KwaZulu-Natal
oyoweo@ukzn.ac.za
References
DeGrazia, D. 2003. ‘Identity, Killing, and the Boundaries of Our Existence’.
Philosophy & Public Affairs 31, 413–442.
Hanser, M. 2005. ‘Where’s the Harm in Dying?’ Philosophical Books 46, 4–10.
Johnston, M. 1987. ‘Human Beings’. Journal of Philosophy 84, 59–83.
Marks, C. E. 1981. Commissurotomy, Consciousness & Unity of Mind, Cambridge:
The MIT Press.
McKerlie, D. 2005. ‘The Ethics of Killing’ (Review Essay). Philosophy and
Phenomenological Research, 71, 477–490.
McMahan, J. 2002. Ethics of Killing: Problems at the Margins of Life, Oxford: Oxford
University Press.
Nagel, T. 1971. ‘Brain Bisection and the Unity of Consciousness’, Synthese 22,
396–413.
Parfit, D. 1984. Reasons and Persons, Oxford: Oxford University Press.
Persson, I. & Savulescu, J. 2005. ‘McMahan on the Withdrawal of Life
Prolonging Aid’, Philosophical Books 46, 11–22.
Puccetti, R. 1973. ‘Brain Bisection and Personal Identity’, British Journal for the
Philosophy of Science 24, 339–355.
Shoemaker, D. 2009. Personal Identity and Ethics: A Brief Introduction. Toronto:
Broadview Press.
20 This paper has benefitted immensely from many helpful comments and suggestions. I
am especially grateful to Simon Beck, Jacek Brzozowski and Chris Ifeacho for their support
during the process of writing this paper as well as to Jeff McMahan and Michael Lacewing
both of whom offered critical comments on the original draft of this paper.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Courting the Enemy: McMahan on the Unity of the Mind 105
Sperry, R. W. 1968. ‘Mental Unity following Surgical Disconnection of the
Cerebral Hemispheres’, Harvey Lectures 62, 723–733.
Unger, P. 1990. Identity, Consciousness and Value, Oxford: Oxford University
Press.
Wasserman, D. 2005. ‘Prenatal Harm and Pre-emptive Abortion in a Two-Tiered
Morality’, Philosophical Books 46, 23–33.
Wilkes, K. 1988. Real People, Oxford: Clarendon Press.
Wiggins, D. 1967. Identity and Spatio-Temporal Continuity, Oxford: Blackwell.
Williams, B. 1970. ‘The Self and the Future’. Philosophical Review 79, 161–180.
Downloaded by [UNIVERSITY OF KWAZULU-NATAL] at 23:06 06 February 2014
Article
Full-text available
If we are physical things with parts, then accounts of what we are and accounts of when composition occurs have important implications for one another. Defenders of restricted composition tend to endorse a sparse ontology in taking an eliminativist stance toward composite objects that are not organisms, while claiming that we are organisms. However, these arguments do not entail that we are organisms, for they rely on the premise that we are organisms. Thus, sparsist reasoning need not be paired with animalism, but could instead be paired with other accounts according to which we are composites. The embodied mind account—a version of the brain view—is one such account. Replacing the premise that we are organisms with the premise that we are embodied minds, in arguments that otherwise parallel those supporting animalist sparsism, yields an account according to which composite objects include thinkers, but perhaps nothing else. Since animalism has implausible implications about scenarios which are handled better by the embodied mind account, this approach is preferable to animalist sparsism. Furthermore, the role of mental features in sparsism makes embodied mind sparsism the more reasonable conclusion. Meanwhile, adopting sparsism allows the embodied mind account to dodge objections that may not be as easily avoided by it or other versions of the brain view if not paired with sparsism. These include objections about brains that are not persons, inorganic part replacement, and another form of part replacement that might seem to allow one to get a new brain.
Article
This paper argues that certain central tenets of the traditional theory of the just war cannot be correct. It then advances an alternative account grounded in the same considerations of justice that govern self-defense at the individual level. The implications of this account are unorthodox. It implies that, with few exceptions, combatants who fight for an unjust cause act impermissibly when they attack enemy combatants, and that combatants who fight in a just war may, in certain circumstances, legitimately target noncombatants who bear a significant degree of moral responsibility for a wrong, when the prevention or rectification of that wrong constitutes a just cause for war.