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http://www.elsevier.com/locate/permissionusematerial From Neil Levy and Julian Savulescu, Moral signifi cance of phenomenal consciousness. In: Steven Laureys,

Nicholas D. Schiff and Adrian M. Owen, editors: Progress in Brain Research, Vol 177, Coma Science:Clinical and Ethical Implications, Steven Laureys, Nicholas D. Schiff and Adrian M. Owen.

The Netherlands: Elsevier, 2009, pp. 361 – 370. ISBN: 978-0-444-53432-3

© Copyright 2009 Elsevier BV. Elsevier

S. Laureys et al. (Eds.)Progress in Brain Research, Vol. 177ISSN 0079-6123Copyright r 2009 Elsevier B.V. All rights reserved

CHAPTER 25

Moral significance of phenomenal consciousness

Neil Levy� and Julian Savulescu

Oxford Centre for Neuroethics, Littlegate House, Oxford, UK

Abstract: Recent work in neuroimaging suggests that some patients diagnosed as being in the persistentvegetative state are actually conscious. In this paper, we critically examine this new evidence. We arguethat though it remains open to alternative interpretations, it strongly suggests the presence ofconsciousness in some patients. However, we argue that its ethical significance is less than many peopleseem to think. There are several different kinds of consciousness, and though all kinds of consciousnesshave some ethical significance, different kinds underwrite different kinds of moral value. Demonstratingthat patients have phenomenal consciousness — conscious states with some kind of qualitative feel tothem — shows that they are moral patients, whose welfare must be taken into consideration. But only ifthey are subjects of a sophisticated kind of access consciousness — where access consciousness entailsglobal availability of information to cognitive systems — are they persons, in the technical sense of theword employed by philosophers. In this sense, being a person is having the full moral status of ordinaryhuman beings. We call for further research which might settle whether patients who manifest signs ofconsciousness possess the sophisticated kind of access consciousness required for personhood.

Keywords: consciousness; persistent vegetative state; minimally conscious state; morality; right to life;access consciousness; phenomenal consciousness

Consciousness is notoriously difficult to study significantly, on the consciousness of the patient.empirically. But unlike most other nearly intract- Opponents of withdrawing life support oftenable problems, consciousness matters. It matters claim that PVS patients are conscious, citingpractically to the quality of our lives, but also for spontaneous behavior by these patients as evi-significant ethical questions. Consider the vexed dence; supporters of the right of family to with-question concerning the withdrawal of the means draw life support maintain that PVS isof life (whether life support or nutrition and incompatible with consciousness. Given this con-hydration) from patients in a persistent vegetative text, the recent claim by Owen et al. (2006) thatstate (PVS). As we recently witnessed in the Terri they have strong evidence of consciousness in aSchiavo case, these cases are the focus of PVS patient is extremely significant.passionate debate, and this is a debate that turns, In this paper, we shall sound a note of caution.

While the results reported are undoubtedlysignificant, and leave little room for doubt thatsome patients correctly diagnosed as PVS (i.e.,�Corresponding author.who do not show the minimal behavioral respon-Tel.: +61 3 8344 3855; Fax: +61 3 8344 4280;

E-mail: neil.levy@philosophy.ox.ac.uk siveness required for another diagnosis) have

DOI: 10.1016/S0079-6123(09)17725-7 361

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some degree of consciousness, their ethicalimportance should not be exaggerated. We shallargue that given the current state of our knowl-edge — a state which is, we acknowledge, influx — the research is unlikely to significantly alterthe ethical debate. If PVS patients are conscious,then it is important to ensure that they do notexperience aversive mental states. Accordingly,we have reason to give their analgesics andperhaps sedatives and antidepressants. Butwhether they are conscious or not, it can beargued that we have little reason to maintain themin existence (and perhaps even some reason tobring about the cessation of their lives), unlesstheir mental states are at least as sophisticated asthose exhibited by children, and, importantly, asconnected across time. It is not merely conscious-ness that is required for what we shall call fullmoral status; it is self-consciousness, and we donot believe that we can (yet) attribute self-consciousness to any PVS patients.

Concepts of consciousness

In order to understand and properly appreciatethe significance of the work of Owen andcolleagues, it is necessary to recognize thatconsciousness is a complex phenomenon, orperhaps even a complex set of phenomena.Different thinkers denote different propertieswhen they refer to ‘‘consciousness,’’ and differentconcepts of consciousness underlie different kindsof moral value. It is likely that the differentconcepts of consciousness refer to properties thatco-occur in normal subjects under typical condi-tions, but given that they may dissociate, innormal and in pathological cases, we cannotassume co-occurrence without further evidence.

What do researchers like Owen mean whenthey say that a patient is conscious? Generallyspeaking, neuroscientists and clinicians implicitlywork with a definition of consciousness that isvague, but which might best be summed as‘‘wakefulness with awareness.’’ Wakefulness isrelatively easily defined, at least behaviorally, andis rarely in dispute. Wakefulness is a definingfeature of PVS: a patient is diagnosed as PVS

when they transition out of a coma and begin asleepwake cycle but remain unresponsive toexternal stimuli. ‘‘Awareness,’’ too, is definedbehaviorally: a patient is aware if they make non-reflexive responses to external stimuli. Theresponse need not be sophisticated: tracking amoving object or even fixated their gaze for longenough to rule out mere chance is enough toindicate awareness. If the response is inconsistent,the patient is said to be in a ‘‘minimally consciousstate’’ (MCS), where to be minimally conscious isto have transitory conscious states (possiblysometimes of a lower quality than the consciousstates of normal subjects). Now, people are free touse words however they like; if they want define‘‘consciousness’’ as ‘‘wakefulness with awareness’’they may do so. But we should be aware thatconsciousness is a word in everyday language.Accordingly, there is a risk that consciousness, asused by neuroscientists and clinicians, will beunderstood as denoting not, or not only, ‘‘wake-fulness with awareness’’ but the other propertiesmore usually associated with consciousness.Indeed, neuroscientists and clinicians themselvesseem to assume that consciousness as they use ithas these further qualities. But this assumptionmay be illegitimate.

What are these further properties? Ned Blockhas famously distinguished two concepts of con-sciousness, both of which, he asserts, have claimsto being the folk concept: phenomenal conscious-ness and access consciousness (Block, 1995).Phenomenal consciousness refers to the qualita-tive character of experience. A state is phenom-enally conscious inasmuch as there is something itis like to be in it. In contrast, information is accessconscious if it is available for rational control, if itis simultaneously accessible to the decision mak-ing, planning, and volitional centers. Many neu-roscientists seem committed to a globalworkspace model of consciousness (Baars, 1988,1997; Dehaene and Naccache, 2001). On theglobal workspace account, information is con-scious if it is in the global workspace, that is,simultaneously accessible to a variety of (so-called) consuming systems. Consuming systemsare relatively modular and possess few links toone another; only through the conduit of the

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global workspace does information became avail-able for the rational control of thought andbehavior.

Now, it is apparent that the participants in thedebate over whether some patients diagnosed asPVS are conscious assume that consciousness, asthey define it and test for it, has the properties thatBlock describes, that is, a patient who exhibitswakeful awareness is both phenomenally con-scious and access conscious. For instance, theyargue, on the basis of their evidence, that there iscase for giving PVS patients analgesia (Whyte,2008); since the function of analgesics is to mitigatethe experience of pain, they clearly assume thatwakeful awareness is evidence of phenomenality.Now, in general this is a warranted assumption:the three concepts of consciousness (wakefulawareness, phenomenality, and access) occurtogether with great regularity. But it may be thatthese different states can dissociate. Block hasargued that sometimes the contents of thephenomenal consciousness of normal subjects arericher than the contents of their access conscious-ness; that is, they have phenomenal contents thatare not available to the full range of consumingsystems which have access to the global workspaceof access consciousness. The opposite dissociationis also conceivable, that is, subjects may sometimesbe access conscious of information of which theyare not phenomenally conscious, perhaps, forinstance, when engaging in overlearned behavior.This being so, we should not be too quick toassume that access and phenomenal consciousnessco-occur in the patients tested. Thus, one chal-lenge to researchers aiming to show that somePVS patients are conscious is to answer thequestion what kind of consciousness their testsreveal. As we shall see, different answers to thisquestion have dramatically different moral impli-cations.

A second (and more basic) challenge consists inshowing that the evidence produced is of con-sciousness at all. The fact that a test shows thatinformation presented to a subject is available todrive behavior is not evidence of consciousness,all by itself. The mind contains a number of whatwe might call ‘‘zombie systems,’’ modular systemscapable of guiding behavior in response to

environmental stimuli in the absence of conscious-ness. Classic examples include the modulesinvolved in visual perception, which calculatedistance and trajectory of objects and motivatereflexive avoidance behavior. The existence ofthese systems, which may account for a great dealof the behavior of normal awake subjects (Barghand Chartrand, 1999), is a product of ourevolutionary history, in which consciousness wasalmost certainly a relatively late arrival. We werebehaving in adaptive ways for millennia beforeconsciousness arrived, and evolution is a conser-vative process. Consciousness is a scarce resource,one that is apparently called on only when zombiesystems do not suffice on their own; it is neededonly for complex or novel behavior.

Showing that a patient is (relevantly) conscious,therefore, requires conceptual work as well asempirical results. We need to establish whatbehaviors require consciousness, and what kindsof consciousness are required. We also need toestablish the precise relationship between accessand phenomenal consciousness. It may be thatonce access consciousness is rich enough, itscontents are ipso facto phenomenally conscious,but this remains to be demonstrated. We are notentirely ignorant here: at least we have goodtheories concerning the role of access conscious-ness, which may shed light on the relationshipbetween the two concepts of consciousness. Thefunction of access consciousness is likely to be theintegration of information from diverse sources,making that information available to manysystems (including zombie systems) in turn.Information of which a person is aware is accessconscious if it is available to (enough of) theconsuming systems which make up the mind.Information must achieve what Dennett (2001)calls ‘‘cerebral celebrity’’ in order to be accessconscious. It may be that achieving this kind ofcelebrity is also necessary for phenomenal con-sciousness; perhaps, the richness or vividness ofphenomenal consciousness is a function of thedegree of global availability of information. Themark of access consciousness is flexibility ofresponse; because a piece of information isglobally available, it can drive different kinds ofbehavior, and behavior that is sensitive to many

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different kinds of information, fed from differentmodules. Mere awareness, or mere response, istherefore not an indicator, by itself, of conscious-ness. Isolated zombie systems are perfectly cap-able of such responses, but isolated zombiesystems are unlikely, by themselves, to give riseto any kind of consciousness.

If all this is correct, we have good reason to besuspicious of the standard behavioral tests for thedetection of consciousness. At very least, their userequires validation; it must be shown that thebehaviors in question are unlikely to be producedby zombie systems. One of the many reasons whythe work of Owen and colleagues constitutes anadvance on standard methodologies for thedetection of consciousness is that they aresensitive to this kind of concern; the task theyuse is demanding enough to make the hypothesisthat it is accomplished by zombie systems aloneunlikely.

Consciousness: new evidence

Owen et al. (2006) represents a revolution inconsciousness studies, not only in the resultscontained but also in the methodology employed.Previously, researchers who hoped to detectconsciousness in patients who, for one reason oranother, were unresponsive to external stimulihad used fMRI or EEG in an attempt to detectneural correlates of consciousness ‘‘the minimalset of neuronal events and mechanisms jointlysufficient for a specific conscious percept’’ (Koch,2004, p. 16). This is a technique fraught withconceptual difficulties, inasmuch as it is disputedwhat neural processes constitute the correlates ofconsciousness. Owen et al. sidestep this debatebrilliantly. We can reconstruct their reasoning asfollows: we do not ordinarily look for the neuralcorrelatives of consciousness in other people,because we believe that the kinds of complexcognitive processes in which they manifestlyengage — talking to one another paradigmati-cally, but also interacting flexibly with theenvironment in ways that outrun overlearnedprocesses — are clear evidence of access con-sciousness, and almost certainly of phenomenal

consciousness as well. It is therefore not necessaryto look for the neural correlates of consciousness.Instead, neuroimaging techniques can beemployed to look for neural correlates of lesscontroversial processes; if the subject givesunequivocal evidence of engaging in complexprocesses, of the sort which we ordinarily take tobe evidence of consciousness, we will have asgood reason to attribute consciousness to them asto one another outside the clinical context.

The reasoning is, we think, unassailable. Ifthere are any doubts about their results, thesedoubts must focus on the particular cognitiveprocesses selected, and on whether these pro-cesses might be carried by zombie systems, andnot on the general line of argument. Let us nowturn to the processes and the evidence they haveproduced.

There were two kinds of probes utilized byOwen and colleagues. One tested for, andsuccessfully demonstrated, appropriate processingof ambiguous words. This evidence is not espe-cially informative, because semantic processing isclearly the kind of thing that can be carried out byzombie systems. A number of previous studieshave shown task-specific brain activation inpatients: Schoenle and Witzke (2004) measuredevent-related potentials in the brains of PVSpatients, using sentences ending in congruent orincongruent words as stimuli. In normal controls,an N400 response is elicited by the incongruentendings. Twelve percent of VS patients and 77%of what the authors describe as near VS patientsexhibited the response, reflecting preservedsemantic processing in these patients. Unpub-lished data reported by Perrin showed a P300response — correlated reliably with recognition —to the patient’s own name in PVS (Laureys et al.,2005). The evidence from Owen et al. of semanticprocessing in PVS is therefore unsurprising.Semantic processing is mental activity, but mentalactivity need not be conscious.

The second type of probe utilized produces farmore impressive evidence, and attention hasrightly been focused on it. The probes utilizedwere instruction probes, and came in two variants.One variant asked the patient to imagine playingtennis, while the other asked her to imagine

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walking from room to room in her house. In eachcase, she was asked to engage in the task for 30 sat a time. During the tennis probe, significantactivity was observed in the supplementary motorarea (SMA); during the navigation task, activitywas observed in the parahippocampal gyrus, theposterior parietal cortex, and the lateral premotorcortex. In both cases, the responses were compar-able to those observed in healthy controls.

The tasks the patient was asked to performmatters relatively little; any task would do, so longas it satisfied two conditions: initiation of the taskmust be under voluntary control and it must giverise to unambiguous neural correlates. It isplausible to maintain that the instruction follow-ing probes both satisfy these conditions (though itis sufficient for their purposes if only one of themsatisfies the conditions). Might the behavior havebeen carried out by zombie systems nevertheless?Some critics have worried that the behavior mightbe produced through priming (Greenberg, 2007),that is, the processes which, in normal subjects,lead later behavior to be responsive to uncon-sciously processed information. In response,Owen et al. (2007) point to the sustained natureof the activity. Priming, they argue, is typicallytransitory, not sustained for the full 30s. But thisreply is not decisive.

Owen and his critics seem to have the sameview of the unconscious: it is the ‘‘dumb’’unconscious of cognitive psychology, whichengages in brief flickers of automatic behavior.But the view of the unconscious mind suggestedby work in social psychology is of a set of flexibleand complex systems, capable of driving intelli-gent behavior. Most of the actions of ordinarypeople — some researchers believe the over-whelming majority — are initiated and guided byunconscious systems. Consciousness is a limitedresource and it is saved for difficult tasks. So thereis another way to interpret the evidence: ratherthan inferring, with Owen et al., that the patientengaged in goal-directed and complex behavior,and thus must have been conscious, we canconclude that they have provided further evidencefor the power of automatic systems.

Owen et al. argue that their study demonstratedthat the patient was conscious because the

activation in SMA and other regions persisted solong, whereas responses to primes last only a fewseconds. But persisting activity by unconsciousprocesses has been demonstrated: Bargh et al.(2001) primed subjects with stimuli related to highperformance, put them to work on a word findingtask, and then instructed them to stop after 2 min.Primed subjects were more likely to ignore theinstruction, indicating the persistence of theunconsciously activated goal. In a variation ofthis study, primed subjects were interrupted at thetask after 1 min and then made to wait 5 minbefore being given the choice of continuing theword finding task or instead performing a cartoon-rating task, which was rated as more enjoyable.Once again, subjects primed with stimuli relatedto high performance were more likely to return tothe word finding task then controls, indicating thepersistence of the unconsciously activated goalthrough a full 5 min of rest.

Of course, this study is in many ways disanalo-gous to Owen et al., most significantly in that itconcerned fully conscious subjects, albeit withunconsciously primed attitudes. Nevertheless, itdemonstrates that we cannot infer from the merepersistence of a mental state to the conclusion thatit is conscious. There is also some evidence thatinstruction following can be performed in theabsence of consciousness, this time by subjectswho may be entirely unconscious. Automatism ischaracterized by complex goal-directed behavior,apparently in the absence of consciousness.Automatism can persist for long periods of time.Consider the case of Ken Parks, who in 1987drove 23 km through the Ontario suburbs to thehome of his parents-in-law, where he stabbedthem both (Broughton et al., 1994). Parks washeld to be acting automatistically. Behavior inautomatism is less flexible and intelligent thanconscious behavior; some researchers believe thatthe violence sometimes observed arises from anunexpected obstacle interrupting an overlearnedscript. But it is apparently compatible withinstruction following, at least in an extendedsense: Parks drove through the Ontario streetsapparently safely. We do not know if he obeyedthe instructions of traffic lights and stop signs, butat very least he was able to guide his actions by

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the layout of the streets, all in the apparentabsence of consciousness.

It should be noted that though the existence ofautomatism is not in doubt, there is little directevidence of the absence of consciousness insubjects in this state. However, if the widely heldtheory according to which consciousness requiresactivation of higher-associative cortices is correct(Dehaene et al., 2006), subjects in a state ofautomatism are not conscious, since they do notexhibit such activation (Laureys, 2005).

Despite the reservations expressed above, weconcede that the evidence presented by Owenet al. (2006) is impressive. It is indicative ofa degree of complexity of behavior which isunexpected. It is evidence of instruction following,and there are grounds for regarding instructionfollowing as evidence of consciousness. Thoughthe objection from priming cannot be ruled out, itmight be thought that on balance the evidencefavors the view that their patient was conscious-ness. What kind of consciousness is in question?Instruction following is evidence of some degreeof access consciousness, the kind of consciousnessthat makes possible verbal report in normalsubjects. Indeed, the PVS patient is engaging inan unusual kind of verbal report. It is a furtherstep from the claim that the subject is accessconscious to the claim that she is phenomenallyconscious. It remains possible, as we have seen,that zombie systems underlie the report, andfurther work which tests for this possibility isrequired (Block, 2005, 2007, suggests way inwhich the dissociation between access and phe-nomenal conscious may be empirically tractable).However, given our doubts about the actualdissociation of the kinds of consciousness, wethink it is reasonable to conclude that the patienthas some degree of phenomenal consciousness aswell as access consciousness.

The moral significance of consciousness

Even though we think that Owen et al. haveproduced impressive evidence that patients cor-rectly diagnosed as PVS (i.e., who do not showsufficient behavioral responsiveness to qualify as

conscious on the standard tests) are sometimesconscious, we want to sound a note of cautionover the moral significance of these findings. Wethink that the moral issues are hardly altered at allby the findings.

The distinction between the two concepts ofconsciousness is important for ethics as well ascognitive science and the philosophy of mind.Consciousness is closely linked to the moral statusof those capable of experiencing it, but thedifferent kinds of consciousness underlie differentkinds of moral value. Phenomenal consciousness issufficient to make its bearer a moral patient(though it may not be necessary — beings withinterests, like plants, who lack phenomenal con-sciousness might be moral patients as well; if so,however, they are a very low-grade kind of moralpatient). To be a moral patient is to be a beingwhose welfare matters, whose welfare must betaken into account when we decide what to do. Tobe phenomenally consciousness makes one a moralpatient because a phenomenally conscious beingcan experience states that have qualities of aver-siveness (like pain or boredom) or of pleasantness(like joy); these are states that matter intrinsically.To undergo these states is to have experienceswhich matter morally, and therefore beings capableof such experiences are moral patients.

We cannot be indifferent to moral patients; weare required to take their morally relevant statesinto account when we decide how to act. If PVSpatients are sentient, then it matters what we doto them. We can benefit them by giving pleasureand harm them by causing pain. To that extent,their moment-by-moment states are of potentialvalue and disvalue to them: they can suffer on theassumption — contra Carruthers (2004) — thatthe badness of pain consists in its phenomenality.We are morally required to minimize the amountof pain suffered by any sentient being (to theextent to which this is compatible with our othermoral obligations), where sentience is the abilityto have phenomenally conscious states. One wayin which the findings under discussion shouldaffect the debate, therefore, is by indicating theuse of analgesics for some PVS patients. Theymay suffer, and we ought to take steps to preventor minimize their suffering.

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In our view, being a moral patient solely on thegrounds that one is capable of experiences thatare aversive or pleasant is a relatively low grade ofmoral status. It is the status that we accord tononhuman animals. It is widely, and in our viewcorrectly, held that we ought to take the quality ofthe experiences of nonhuman animals intoaccount in our decision making, such that, say,we cannot cause them pain unless we have a goodjustification for doing so. But it is also widely, andwe think correctly, held that other things beingequal we have little reason to maintain nonhumananimals in existence; we need little justification to(painlessly) kill them (that is not to say, of course,that there are no differences between non-human animals and human beings: in virtue ofhaving been a person, a certain kind of respectfultreatment might be due to a patient, for instance,most of us think people ought to be buried. Ourclaim, rather, is nonhuman animals and humanbeings who are merely moral patientsare similar in lacking an interest in continuingto live).

According to the view we are urging, nonhu-man animals, with the possible exception of thegreat apes and perhaps cetaceans, have a right tohave their interests taken into consideration, butthey do not have a right to life. By a right to lifehere we do not mean the full inviolability thatdeontologists mean by the phrase: we do notmean an inviolability that can only be defeated bynothing short of what Nozick calls ‘‘major moralcatastrophe’’ (Nozick, 1974). We mean somethingless stringent: a right to inviolability that can bedefeated only by a sufficient number of compar-able goods. We do not have space to develop ourconception of what it takes to defeat such a righthere; suffice it to say that this is a right that cannotbe defeated by any number of trivial interests,though it can be defeated by important goods.Nonhuman animals do not have any such right;they have no interest in continuing to live andtherefore we can choose to kill them (once again,painlessly) for the satisfaction of trivial interests(other things being equal), normal adult humanbeings do have such a right. What is it aboutnormal adult human beings that justifies thisdifference in their moral status?

The justification lies in the mental states ofwhich they are capable, including, though notonly, their conscious mental states. The life of aperson typically matters much more than the lifeof a nonhuman animal because only the former iscapable of very sophisticated mental states thathave an ineliminably temporal component. Abeing acquires a full moral status, including theright to life, if its life matters to it; that is, if it is notonly momentary experiences that matter — as forthe being capable only of phenomenal conscious-ness — but also an ongoing series of experiences.A full right to life requires that it is not onlyexperiences that matter to one, but also how one’slife actually goes; that is, that satisfaction of one’sinterests matter to one, and this requires verysophisticated cognitive abilities, such as an abilityto conceive of oneself as a being persistingthrough time, to recall one’s past, to plan, and tohave preferences for how one’s life goes (Singer,1993; McMahan, 2002). It is the connectednessand continuity of one’s mental states that under-write personhood, in one central sense of theword; it is insofar as each of us is a single beingacross (relatively long) stretches of time that wecount as moral persons.

But the abilities that underlie moral person-hood and full moral status are abilities thatrequire access consciousness, not phenomenalconsciousness. Information must be sufficientlyavailable for rational thought and deliberation inorder for a being to be able to have future-oriented desires or to conceive of itself aspersisting in time. So the demonstration that thePVS patient was phenomenally conscious — thatis, that she was ‘‘consciously aware of herself andher surroundings’’ (Owen et al., 2006, p. 1402) —would not alter the debate significantly unless itwas also evidence for sophisticated cognitiveabilities, including a sophisticated kind of accessconsciousness that was not the subject of evalua-tion of the Owen tests.

In order to justifiably attribute to a being the rightto life, in the sense sketched above, we must havegood reason to attribute to them not phenomenalconsciousness, but a sophisticated kind of accessconsciousness. It is not sufficient that information bein the global workspace; there is every reason to

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think that this much is true of many nonhumananimals, including many who are not capable of thesophisticated mental states required for a right tolife. In addition, as we have seen, the right kinds ofinformation must be available to the right systems toenable the organism to have extended and self-referential mental states. The organism must becapable of future-oriented desires (desires that somefuture state of affairs be actual) and, of plans andprojects. It must be capable of preferences regardinghow its life goes. These capacities require that theorganism be capable not merely of phenomenal andaccess consciousness, but also of self-consciousness,because only a self-conscious being can havepreferences regarding how its life goes. This is onereason why most nonhuman animals do not have aright to life, but great apes and cetaceans might,because the latter pass tests for self-consciousness(like the mirror test; the ability to recognize that animage in a mirror is oneself is thought to require aconception of oneself as a separate being; seeKeenan et al., 2003) and the former do not.

In addition, however, it is plausible to think thata full right to life requires not just accessconsciousness — which, as we noted above, wethink that patients who pass the tests designed byOwen et al. demonstrate — but a sustained andsophisticated kind of access consciousness; that is,for a being to possess a right to life, theinformation in their global workspace must beavailable to consuming systems for a sustainedperiod, to enable the being to link mental statesacross time. It may in fact be the case that what weshall call diachronic access consciousness is anecessary condition of self-consciousness that onlya being who is able to maintain a thought about adesire can refer that desire to itself and thereforebe self-conscious. There is, we note, evidence forsome kind of diachronic access consciousness inthe patient reported in Owen et al. (2006); thepatient sustained the instruction following task fora full 30s. But before we can conclude that she isself-conscious, we need evidence that her dia-chronic access conscious had the right content:that it included self-referential contents. So faras we can tell, the study does not provide suchevidence, and therefore does not establish that the

patient has the right kinds of sophisticated mentalstates that underlie full moral status.

Conclusion and future directions

Clearly, further research is needed. We do notrule out the possibility that some patients whopass the test are in a state akin to locked-insyndrome, in which, usually as a result of a brainstem stroke, a person is fully and normallyunconscious but incapable of voluntary move-ment. Someone in this state has all the capacitieswhich underlie a full right to life. But we do nottake this claim to be established. We haveexpressed some doubt that the patient in theoriginal study was conscious at all, but we concedethat the room for doubt is limited. We do thinkthat the evidence suggests strongly that some PVSpatients are actually conscious. But we think thatthe degree of consciousness is likely to be closerto that seen in MCS, rather than in LIS. We havesuggested that the transitory and fluctuatingconsciousness seen in some MCS patients doesnot underwrite full moral status because it istransitory; only in those cases in which the mentalstates of the person are appropriately connectedto one another does she have full moral status.

If the patient is conscious, then she is a moralpatient; it matters — morally — how we treat her.We cannot cause her pain unless there is goodreason to do so. But we do not have a reason tomaintain her in being. Indeed, given that decisionsabout patient treatment are made in contexts inwhich resources are scarce, evidence that thepatient is neither self-conscious nor capable ofself-consciousness might be seen to be evidencethat we have a positive reason not to maintain herin being (we acknowledge, of course, that there isno direct evidence that any PVS patient is notconscious). But we utterly reject the view that weneed evidence for the absence of consciousnessbefore we can justifiably conclude that conscious-ness is lacking. Sometimes absence of evidence isevidence of absence; were that not the caseinduction, a fundamental part of the scientificmethod in which one concludes on the basis of the

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fact that past experiences have had a certainfeature that future experiences will too would beimpossible (for a defence of this claim, see Sober,1981). Given the current state of consciousnessstudies, we believe that we can — fairly — reliablyconclude from the absence of certain kinds ofneural responses to the absence of states ofconsciousness.

We conclude with some reflections on themoral importance of the research examined here,as well as related work. We have argued thatif the research shows that the patient is phenom-enally consciousness but not self-conscious, wehave reason to take her experiences into con-sideration but not to keep her alive. But we havenot ruled out the possibility that some PVSpatients will be shown to have more sophisticatedcognitive capacities, which would allow us justifi-ably to attribute full moral status to them.Moreover, it may be that evidence of conscious-ness in PVS is not evidence of full moral status atthe time of the test, but predictive of laterrecovery, perhaps even recovery of full moralstatus. Obviously, we have good reason tomaintain a person in life if they have goodprospects of such a recovery. Given, however,that MCS (unless it is a transition stage) is not astate that gives a patient moral personhood, it isno benefit to them to be in it.

Obviously, a great deal of further research isnecessary. In particular, we hope to see researchaimed at demonstrating the sophisticated kind ofaccess consciousness that underlies full moralpersonhood. Such tests would demonstrate theavailability of self-referential information to thepatient across time; they would therefore probefor desires which are about how the patient’s lifegoes, and not merely for immediate experiences,for hopes or fears regarding future times. We seeno way to test for these capacities without thedevelopment of a communication paradigm thatwould enable the probing of self-consciousnessand temporally persisting information. Unfortu-nately, we believe that this is a case in whichfailure to elicit the information would not beabsence of evidence that is evidence of absence:there are many reasons why someone who is

conscious might fail to be capable of sophisticatedcommunication. But success at eliciting suchinformation would put the moral status of PVSpatients beyond any doubt.

References

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