Do I still owe a promise to the man who no longer remembers it?

We were driving back from visiting his mother, who had just moved into a care home in Bangor. He was quiet for most of the road and then said, without looking at me: "Promise me you'll never put me in one of those places." I said I promised. It was the kind of thing people say in cars. I did not think about it again for nearly twenty years.

Four years ago he was diagnosed with Alzheimer's disease. Today he does not remember his mother's care home, or the drive, or asking. Some days he does not remember that I am his wife, though he is always glad to see me. The promise is now entirely mine. He cannot release me from it, because he does not know it exists. And the day is coming, probably within a year or two, when keeping it may be beyond me.

I have read a fair amount of philosophy in the evenings since then, mostly to find out whether I am allowed to break it. This is what I have found.

Is he the man I promised?

The first answer philosophers give is to ask whether the person in front of me is the same person who extracted the promise. John Locke, in the chapter on identity in his Essay, tied personal identity to consciousness reaching back through memory: I am the same person as the one whose actions I can remember as mine. On a strict reading of Locke, the man who asked for my promise and the man who now asks me what day it is are not the same person, because the second cannot reach back to the first.

I do not find this comforting, and I don't think I am supposed to. It would mean that the man I made the promise to has, in a sense, died, and that I am looking after someone else. Some days it feels like that. Most days it does not. He still laughs at the same things, hums the same hymns, folds his napkin into the same small square. Locke's test asks about memory. My husband is made of more than his memories.

Derek Parfit, in Reasons and Persons, argued that identity is not what matters in survival; what matters is psychological connectedness and continuity, which come in degrees. That fits my experience better. My husband is less connected to the man in the car than he was, but not cut off from him. The promise was made to someone he is still partly continuous with. Whether "partly" is enough to bind me is precisely what I cannot work out.

The earlier self and the present one

The legal philosopher Ronald Dworkin, in Life's Dominion (1993), gave the strongest argument for keeping faith with the earlier self. He distinguished experiential interests, in having good experiences now, from critical interests, in our lives going as we judged they should go as a whole. A person who has lost the capacity to form such judgements, he argued, keeps the critical interests he formed when he could. Respecting his earlier wishes is respecting his authority over his own life, which he called precedent autonomy.

On Dworkin's view my promise is strengthened, not weakened, by the illness. My husband, when he could judge, judged that he did not want to end his life in a home. The man who cannot now judge is not in a position to overrule him.

Against this, several writers have argued that the present person has interests too, and that the earlier self should not be allowed to tyrannise over a later one who may be quite content. Dworkin's own most discussed example was a woman called Margo, described by a medical student who visited her: she had advanced dementia and seemed, by every outward sign, happy. If Margo had once written that she would not want to live like that, should her happiness count for nothing?

I see both sides at my own kitchen table. If a good care home would leave my husband safer, calmer and better looked after than I can manage at three in the morning, then keeping the promise might serve the man in the car and harm the man in the chair. Dworkin would tell me to honour the first. Everything in me that was a primary teacher tells me to look at the second.

What a promise to a person is

I have come to think both arguments miss something, and I found it in two women's books rather than in the debate about identity.

Eva Kittay, writing about caring for her severely disabled daughter, argues that all of us are, in her phrase, some mother's child: dependent at the beginning and often at the end, and owed care because we are bound up with those who care for us. Her point is that care is a relationship with obligations running in both directions, not a service delivered to a person whose identity has to be established first.

And Iris Murdoch, whom I came to through her husband's account of caring for her, wrote in The Sovereignty of Good about the effort to direct a just and loving attention on another person as they really are. Not as they were, and not as a case.

Together they suggest a different way to read my promise. When he said "promise me", he was not dictating the terms of a contract to be enforced against his later self. He was asking me not to abandon him. He was afraid of being left among strangers by the person who loved him. That fear, I think, is something he still has, even though he could not name it, and that is the part of the promise that binds me.

If that is right, then what I owe him is not a particular address. It is that he will not be abandoned. If the day comes when he must move, I can keep that promise by going with him every day I can, by making sure the people there know he folds his napkin into a square, by not letting him become a stranger. That is not the letter of what I said in the car. I hope it is what he meant.

Where that leaves me

I may be rationalising. Every carer who has broken a promise like this has probably told herself a story like mine, and some of the stories were kinder to the carer than to the cared-for. The card on personal identity sets out the theories, and none of them settles my case. But the threads here have helped me see that the question "is he still the same person?" was never quite my question. Mine is: "am I still keeping faith with him?" That one I have to answer every day, and I can.