Qualitative and numerical identity, and the narrative view

One of the fundamental distinctions in theory of personal identity is that of qualitative identity and numerical identity.1 Parfit19 used the metaphor of billiard balls to distinguish between the two types of identity in a colourful way:

[T]wo white billiard balls are not numerically but may be qualitatively identical. If I paint one of these balls red, it will cease to be qualitatively identical with itself as it was. But the red ball that I later see and the white ball that I painted red are numerically identical. They are one and the same ball. We might say, of someone, ‘ After his accident, he is no longer the same person’ . This is a claim about both kinds of identity. We claim that he, the same person, is not now the same person. This is not a contradiction. We merely mean that this person’s character has changed. This numerically identical person is now qualitatively different. [Parfit, pp. 201–202]19

Simplistically put, one may say that numerical identity is the identity of who we are (as opposed to another individual), and qualitative identity is that of how we are. Now, while empirical work tends to focus on qualitative and narrative aspects of identity, theoretical philosophical work tends to focus on numerical identity: the persistence of a person as a specific individual. Arguably, we accept that we change (qualitatively) over time, as we live our lives, while to ‘change’ numerically is one of our greatest horrors—as it seems to mean that we cease to exist altogether. Therefore,concerns about personal identity as a moral value at stake tend to be about numerical identity.

In recent years, however, voices have been raised against this focus on numerical identity. Jecker and Ko,20 conceding that numerical identity does hold some value for certain things in life, argue:

We regard ourselves not merely as individuals persisting over time, but also as persons leading lives. Leading a life requires unifying events in our lives by selecting, interpreting, and weaving them into an intelligible plot, with beginning, middle, and closing chapters. We impart meaning, for both ourselves and those around us, by situating what we do and want within the context of a meaningful self-told story. A person’s narrative shows who that person is, and how that person understands his or her central desires, goals, and personality.[Jecker and Ko, p. 161]20

This critique from Jecker and Ko echoes the main standpoint of narrativist theory of personal identity: we should understand our identities as coherent, self-told stories.21–23 There is an idea behind the recent support of narrative identity theory that this is the kind of identity—let’s refer to it as ‘narrative identity’—we actually care about, and that it is also more practical: if a person feels that she can tell a coherent story about her life with which she identifies, identity is undisrupted.24

There are at least three reasons why this approach appears incorrect and/or insufficient for our purposes. First, and fundamentally, for there to be a coherent self-told story to be told, there must be a numerically identical person to tell it. If there is no person to tell the story, it can by definition not be self-told—because there is no self present. In the same fashion, if there is another person (numerically) telling the story, it cannot be self-told—because the story would not be about the self.2 In this way, it appears that if narrative identity matters, numerical identity should matter at least as much, as it is a necessary condition for there to be a narrative identity at all.3 In this indirect way, we should care about numerical identity if we care about narrative identity.

Second, numerical identity appears to matter also in a more direct manner. Consider a hypothetical case where our coherent story would be told by another person than ourselves. Just because someone thinks that they are us, and believe they are talking about their own life when telling our story, it doesn’t mean that they are us.4 It is also conceivable that we are unable to form a coherent story about our own lives: perhaps memories conflict, or have been blurred over the years, to a point where there is no ‘intelligible plot, with beginning, middle, and closing chapters’.20 Does this mean that we have ceased to exist? On the contrary, it seems—at least prima facie—that we can retain our identity even if our memories, dispositions and attitudes over time have become somewhat scrambled and distorted.

Third, although narrative identity accounts allow us to inquire with patients directly in matters regarding their identity, it is not clear that the approach is practical in the context of age-related neural decline and disease. We are often faced with cases where the patient is completely incapable of telling a true and coherent story about her life, or is only able to recount a very select set of sections from it—not seldomly scrambled and distorted—only to later on, often shortly before dying, display clarity and improved ability to access her past. These phenomena are highly problematic on most accounts, but perhaps even more so for narrative identity theory: is the identity relation broken, solely because the person cannot accurately tell a coherent story about herself at all times? Or can it be ‘on a break’ as it were?25 The simple (or, perhaps, simplistic) solution that would make the narrative approach practical—to use the response of the patient as the main evidence of identity—backfires immensely in cases like this, and more generally in dementia. For these reasons, a narrative approach is not sufficient to account for personal identity in the context of age-related neural decline and disease.

That being said, there appears to be something to the original narrativist critique, namely the traditional accounts’ focus on numerical identity alone, and dismissal of qualitative identity as a reliable indicator of identity in persons. Or, rather, the tendency to dichotomise the distinction between qualitative and numerical identity.26 Recalling the quote above from Parfit, [pp. 201–202]19 to say: ‘after his accident, he was no longer the same person’, is not a contradiction. It is not clear why there is a tendency in literature to claim that one kind of identity (usually numerical) is more important than the other. Furthermore, it is not clear that it makes much sense to separate the numerical identity (that someone is (not) numerically the same person) and qualitative identity (how someone is as a person) so clearly in cases of dementia. Rather, I will argue, it is vital for our understanding of identity in dementia that we seek to understand the relationship between numerical and qualitative identity.

Consider the following two sentences:

1. Lately, my father is no longer the same person.

2. That is no longer my father.

These are two sentences which could very well be taken from conversations with, say, the children of parents with progressive dementia. On the surface, the two sentences mean roughly the same thing. But if we truly take the phrasing seriously, there is an existential and ethically charged difference between them. One (1) appears to be about a numerically identical person whose qualitative identity has been severely altered. The other (2) seems to be about a person who is no longer numerically identical to a person who used to inhabit the same body. What is the most interesting for us here is not the phrasing itself—it is not a play of words. What is crucial here, is that the sentences are expressions of how the same process (progressive dementia) can result in distinct phenomena. Sometimes at different points in time, sometimes simultaneously but from different perspectives. But it is the same forms of decline, the same diseases, that eat away at both numerical and qualitative aspects of the identity of a person—at least on many accounts of personal identity. As McMillan puts it: ‘Given that dementia has a profound effect on an individual’s mental life, it is entirely possible they may change so much that it raises serious doubts about whether there exists the degree of psychological continuity and connectedness necessary for numerical personal identity.’2 We shall soon have a closer look at what this might mean for the purpose of defining personal identity in this context. For now, let us settle with the notion that, although narrativist accounts of personal identity highlight the problematic distinction between numerical and qualitative identity, they are not sufficiently helpful in addressing ethical issues related to personal identity in dementia care and treatment. Typically leaving the numerical aspects of identity downplayed or ignored, they risk to be misleading in decision-making processes and caregiver support. Let us look have at some other options.

The strengths of Embodied Mind Theory

There are many accounts in the literature of personal identity over time, all with various advantages and disadvantages. Let us first distinguish between two of the main streams in contemporary philosophy of personal identity.

First, we have Psychological Continuity Theory.5 Having been around since at least the days of Locke27 in the form in which we know it today, PC Theory gained ground over the last few decades through the works of philosophers such as Shoemaker and Lewis,28 29 and was perhaps most famously championed by Parfit.19 It has grown to become one of the most widely supported approaches to understanding and theorising personal identity over time,30 and typically stresses the continuity of a specific psychology as the main factor in identity retention over time. We can formulate a generic account of personal identity over time according to psychological continuity theory like so: the persistence of a person over time requires that certain psychological relations hold for a specific person across a given amount of time. That is, person X at t1 is identical to person Y at t2 if and only if a certain relation P holds between X at t1 and Y at t2. Exactly what that psychological relation P must contain is a matter of dispute among proponents, but it commonly includes memories, attitudes and/or values.

Second, we have a family of theories which one may refer to as Brain Identity Theory.6 In this school of thought, what marks the continued identity of a person is the persistence of the ‘container’ of psychological content. The most prominent proponent of this view, on a theoretical level, is Nagel, but the view is arguably fairly prevalent in the neurosciences in general.17 18 31 We can formulate a generic account of personal identity over time according to BI Theory as saying: we are our brains, or certain parts of our brains, and our identity relies on the persistence of those (parts of our) brains over time.

Both BI Theory and PC Theory provide us with intuitively appealing expositions of how we might best understand persistence of identity over time. Starting with PC Theory, Parfit’s account is today arguably the most well known and frequently referred to. His criterion for personal identity over time is formulated as follows:

The Psychological Criterion: (1) There is psychological continuity if and only if there are overlapping chains of strong connectedness. X today is one and the same person as Y at some past time if and only if (2) X is psychologically continuous with Y, (3) this continuity has the right kind of cause, and (4) it has not taken a ‘ branching’ form. (5) Personal identity over time just consists in the holding of facts like (2) to (4). [Parfit, p. 207]19

There are several implications of this account, in the context of dementia, that are worth noting. First, persons typically fade away gradually and slowly, rather than suddenly and rapidly. In the case of Alzheimer’s disease, for instance, there seems to be no clear line where identity is lost or transformed into a new identity. At first glance, this could be problematic: one may think that either identity holds, or it does not (X=Y or X≠Y). But for an account subscribing to the psychological criterion, this is not necessarily a problem per se: we can explain the gradual process of diminishing or shifting identity by looking at the level of connectedness held between a person at different times. If we look at a large timespan, say, t1–t10, it may be that there is strong connectedness between the person at every point in time (A at t1=B at t2, B at t2=C at t6, etc), and yet it may seem that the person at t10 is vastly different—not to say another—than at t1 between A at t1 and J at t10. So, looking solely at the individual qualities over time, the identity of person A may appear to have been altered, broken, or lost, and yet there was no clear point in time when it happened. But this causes a series of conundrums. Most notably, dementias are typically not linear in their progression. It is not unusual for patients to be more connected to their previous selves on some days, and less so on others. What does this mean for their continued persistence? For Parfit, and for many other advocates of PC Theory, the fluctuation of identity is not a big problem. Parfit famously argued that personal identity is not what matters, so we should not care too much about it. What matters, according to Parfit, is the continuum of connected psychology (i.e., (1) and (2) of the psychological criterion).19

Although this is a neat way of avoiding theoretical problems related to PC Theory, it is not a very satisfactory one in practice. The idea that we should in principle not care whether we as individuals cease to exist and are gradually replaced by a person who will inhabit our organism thinking they are us, is arguably difficult to apply in practice. Imagine a dialogue between a caregiver/child (C) and a doctor (D) of a patient (P) suffering from late-stage AD dementia:

C: It is so strange… I can see that P is right there in front of me. And some days I can have a normal conversation with her. But other days, somehow, it does not feel as if she is the same person I used to know. My loving mother, growing up…

D: Oh, she is definitely not. This woman has not been your childhood mother—that person is long gone! Several times over, probably. But don’t worry—that doesn’t matter!

It would just be not only insensitive of a doctor to say such a thing, but also, it appears, incorrect. The swaying of identity in persons living with dementia is something different than the psychological changes we all go through over the course of a life, in that it appears to eat away at a person’s identity. And during this process of withering away, the maintenance and retention of that identity is at the core of our concerns. In this way, it seems that personal identity does matter. Furthermore, these examples suggest that there are certain aspects of identity, and identity change, which are more problematic than others.

BI Theory offers a different set of pros and cons. For Nagel, the most prominent defender of this strand of personal identity theory, there are no indeterminate states of identity—identity always either holds, or it does not, and our brain is solely the determinator of that relation. Or, more precisely, Nagel argues that identity is determined by a certain brain in a certain state:

If […] my mental life depends entirely on certain states and activities of my brain, […] then that brain in those states […] is what I am.[Nagel, p. 41]31

Contrary to Parfit, Nagel argues that personal identity matters quite a bit.7 Life, he argues, can be a wonderful thing—and even when it isn’t, death is worse, as it deprives the victim of any future goods. On Nagel’s account, then, the end of one’s personal identity means death. And if personal identity is determined by our brains, then our death occurs when our brain dies. In this straight-forward way, BI Theory appears fairly intuitive. Changes over time in psychology do not destabilise or erase our identity, so the theory avoids most arguments against Psychological Continuity Theory of personal identity over time.

However, it is not without gaps, particularly in the context of neurodegenerative disease and dementia. One of the main criticisms of Nagel’s BI account is that it does not specify what exactly it takes for me to survive: is it my whole brain?; My brain as it is at a given point in time?; Can another vessel do the job? In the appendix to Reasons and Persons, Parfit highlights this weakness of Nagel’s account: in a case where a person’s brain structure is ‘tampered with’ so that psychological connectedness is lost, it is not clear if she will survive or not, depending on how we interpret Nagel’s brain criteria. If, on the one hand, she is her brain as a whole, and if the brain survived the tampering she would still be alive. If, on the other hand, she is her brain in a certain state, she would plausibly not survive [Parfit, pp. 468–477].19 The key problem is that there is no requirement on a BI account for psychological content, mental states, or the presence a mind for us to continue to exist.

Without digging too deep into the debate between Parfit and Nagel, we can at this point see a clear issue for BI Theory in the context of dementia. First, it appears trivially true that we—as persons persisting through time—survive plenty of changes in our brain. Through plasticity, our brains grow and re-shape throughout life—not only in childhood, or as results of trauma. So, a BI theory should at the very least be able to accommodate for such mundane changes of brain structure. On the other hand, if the continued existence of our brain as a whole is what matters, BI Theory runs the risk of being too permissive: it would imply that a person is alive as long as the brain performs basic motor and life-support tasks, while (perhaps due to traumatic injury, or due to neurodegenerative disease) the brain has lost its capacity for consciousness. Consider yet again the following two phrases.

1. ‘Lately, my father is no longer the same person’.

2. ‘That is no longer my father’.

On an account like the latter, statement ‘2’ is nonsensical, unless the father’s brain has been destroyed or faced whole brain death. This could be a correct assessment, and one can certainly argue for such a position. A major drawback of such a move, however, is that we are forced to accept the ‘survival’ of persons who have irreversibly lost all capacity for an inner life with sensations, thoughts, or experience of actually being alive. While this may be a theoretically coherent position, such a theory seems to be of little practical use in the context of medical decision making. When it comes to the persistence of persons—as opposed to that of inanimate objects—we value the capacity for consciousness. This brings us to a third option. Carrying in mind the benefits and issues associated with both PC Theory and BI Theory, let us consider a third class of identity theory: Embodied Mind Theory. In particular, we shall have a look at the Embodied Mind Account (EMA), as presented by Jeff McMahan:

[ We ] are essentially embodied minds. […] According to the Embodied Mind Account, the criterion of personal identity is physical and functional continuity of the brain. [T]here need only be enough physical and functional continuity to preserve certain basic psychological capacities, particularly the capacity for consciousness. [McMahan, pp. 68–69]7

The EMA has gained a somewhat odd position within the literature on personal identity, in that it appears to not clearly align with any PC Theory or BI Theory, while it at the same time seems to be intimately related to both. On the one hand, what matters for personal identity is the minimal physical and functional continuity of those parts of the brain—whichever they may be—that are necessary and sufficient for maintaining consciousness.8 In this way, McMahan’s account is largely understood as related to Brain Identity accounts.7 21 32 33 ,9 On the other hand, McMahan argues, while personal identity matters to some extent, what matters most is some kind of psychological unity in life, which generates a cause for ‘egoistic concern’: that is, to care about one’s future self as one cares about oneself, rather than as for another. Furthermore, McMahan makes the case that our personal identity and basis for egoistic concern largely coincide, as personal identity itself usually constitutes a sufficient cause for egoistic concern [McMahan, pp. 69–82].7 Also, it is worth recalling, we are after all embodied minds, where the ‘mind’-part arguably is constituted by psychological connectedness and continuity.

This layout gives EM Theory a powerful structure. Unlike many BI accounts, it narrows down which parts of the brain are necessary for the criteria to be satisfied (although vaguely). Additionally, the emphasis on our ‘selves’ as minds, in combination with the inclusion of psychological connectedness as what matters, does at least to some degree correspond to an intuition that our mental lives matter in identity. It also, unlike much of PC Theory, ties our minds and psychological continuity to a specific vessel (the consciousness-regulating parts of our brains), which avoids the improbable conclusion that identity potentially alters several times throughout a normal life. As such, the EMA, as presented by McMahan,7 serves as a strong candidate for a theoretical basis when analysing ethical issues related to dementia and identity. That being said, there are a few implications of the McMahan’s EMA that appear counterintuitive at best, and potentially obstructing ethical decision making in worse scenarios.

A revised EMA

Despite its powerful theoretical foundation, McMahan’s EMA may potentially be ethically problematic in the context of dementias, and emerging methods to prevent and treat these conditions. Here, I will show why I think this is the case, and produce a Revised Embodied Mind Account (henceforth ‘REMA’) aiming to better deal with these contexts.

It is worth noting that McMahan explicitly deals with the prospect of dementia—Alzheimer’s disease in particular—to some extent when elaborating on the EMA. This occurs to some degree when discussing the weaknesses of psychological continuity theory. [McMahan, pp. 43–86]7 He has also written on the topic in other publications.37 However, mainly, his position is declared in the very last section of the very last chapter in his book ‘The Ethics of Killing’, titled ‘The withering away of the self.’7

In general, the EMA entails that a person ‘continues to exist throughout the progress of Alzheimer’s disease, until the disease destroys one’s capacity for consciousness.’ [McMahan, p. 65]7 To support this, McMahan argues that ‘most people’s intuitive view is that, even in cases of dementia or of radical amnesia and personality change, one continues to exist.’[McMahan, p. 257]7 Although it may be true that many people think that we continue to exist throughout even the later stages of dementia, there are at least two problems with McMahan’s assumption. First, data on perception of identity (or ‘self’) persistence in dementia are currently inconclusive.1 Second, studies on the topic all use different definitions of selfhood and/or identity, and criteria of measurement.37 38 This leaves McMahan’s uncited presumption regarding most people’s intuitions with a fairly weak support. Similarly, Lesser39 has argued: ‘people do indeed sometimes talk as if this were the case: ‘He’s not there anymore’ is sometimes said. But it seems fairly clear that, whatever they say, this is not something they literally believe. Indeed, one might suggest that if this were what people really did believe they should be less distressed by the dementia of a relative: it should be easier to accept that a loved person has gone away and been replaced than that they are still here but unable to recognize their family or continue the relationship with them’.

But these (again, unsubstantiated) claims are contradicted by evidence on anticipatory grief in dementia carers, indicating that grief is more prevalent in carers in the months and years prior to the death of the cared-for, than in the months after they have passed.40–42 Granted, the inconclusive and disparate results in studies on the subject also go the other way: there is no evidence that most people don’t have the intuition that we continue to exist in late-stage dementia, or related neurodegenerative conditions. If anything, there seems to be evidence that intuitions on the matter are quite varied.

In a condensed version, McMahan’s view yields the following result in cases of progressive dementia: (1) Identity is preserved in a person until her brain’s capacity to uphold consciousness ceases—at which point she ceases to exist. (2) The disease gradually diminishes the basis for egoistic concern, consisting in the physical, functional and organisational continuity of the brain. Only physical and functional continuity of the brain is necessary for identity persistence. (3) A person in late-stage dementia (‘Demented Patient’, in McMahan’s terminology) may be regarded as ‘merely a fragment’ of her previous self (‘Patient at Onset’, in McMahan’s terminology). [McMahan, p. 494]7 (4) Because of the severed basis for egoistic concern, it would be rational for ‘Patient at Onset’ to care less about herself as ‘Demented Patient’ than she would care about herself was she not to develop dementia.[McMahan, p. 493–496]7

In this manner (1–4), the EMA implies that there is a weaker rational basis for a person A to be egoistically concerned about a person B, while there is at the same time a stronger rational basis for A to be egoistically concerned about A, and A=B. This seems odd.10 Although this makes sense from an EMA perspective (because the determinator of egoistic concern is not mainly the identity relation), it is less clear that it is a plausible position to argue in applied and clinical ethics. At the very least, it appears puzzling to a point where it is likely to obstruct decision-making procedures involving the ethical value of personal identity. For our purposes, this is quite problematic. I therefore take this objection—call it ‘The Identity-Concern Objection’—as counting against EMA as a theory of personal identity in the context of age-related neural decline and disease.

A second objection worth raising here concerns the status of persons who are suffering from severe neural damage due to dementia and related conditions, and what becomes of them if we manage to save them. To illustrate this point, let us consider a hypothetical case.

Towards a unified Embodied Mind Theory

The conundrums of personality, identity and existence that occur in progressive dementia will continue to haunt philosophers until the causes of these conditions are all eradicated. But until then, it is of utmost importance that these concepts can be at least somewhat comprehendible and applicable in dementia care. Many ethical issues in dementia care and treatment, ranging from respecting mundane wishes of persons living with dementia, to advance directives prescribing assisted suicide, rest on these and related notions. In adopting or spreading inaccurate accounts of identity within dementia care and treatment, we risk perpetuating misunderstandings in decision-making processes, and ethically objectionable outcomes in future practices: it is impossible for patients, caregivers and medical professionals to navigate the value trade-offs involved in dementia care and treatment if we do not have an adequate understanding of what those values are—including the value of personal identity over time.

There are many coherent and well-developed accounts of personal identity in the literature, ranging from views stressing the importance of coherence of, and identification with, a personal narrative20–32 or the physical body,47–49 to accounts emphasising (parts of) the brain,17 18 or psychological or mental states and traits.19 33 In this paper, I have argued that, while fundamentally one of the most promising accounts of personal identity over time, McMahan’s Embodied Mind Account of personal identity leaves explanatory gaps in how dementia affects our identity. Without taking anything away from the basic principles of Embodied Mind Theory, I have additionally suggested a way forward through which we may unify the quantitative and qualitative aspects of personal identity over time, to generate a more comprehensive account. The aim of this has been to improve our grasp of some of the odd phenomena occurring in dementia, and some of those which are bound to emerge as we develop ways to treat related conditions over the coming decades.