I am writing a book dealing with Alzheimer’s disease for young people. The protagonist, a boy in the 8th grade, is grappling with his grandmother’s progressing AD. I would be interested on your thoughts about identity/mind and Alzheimer’s disease. Is a person with progressive AD the same person that they were without the disease? Any resource suggestions would be appreciated. The boy is in a philosophy class at his Catholic school and much of his questioning will come through class discussions

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This is a really interesting question. John Locke, in his Essay Concerning Human Understanding, famously defined a person as "a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing, in different times and places; which it does only by that consciousness which is inseparable from thinking, and as it seems to me, essential to it." He then goes on to talk about our personal identity over time: "For, since consicousness always accompanies thinking, and it is that that makes everyone to be what he calls self, and thereby distinguishes himself from all other thinking things, in this alone consists personal identity, i.e., the sameness of rational being; and as far back as this consciousness can be extended backwards to any past action or though, so far reaches the identity of that person."

The notion of consciousness extending backward is often taken to signify memory, and so a Lockean theory of personal identity suggests that person A at time t2 will be the same person as person B at time t1 if and only if person A remembers some experience/s of B's. This Lockean memory theory would thus suggest that, in many cases of progressing AD, the AD patient is not the same person as she was 10, 20, 30 (etc.) years ago -- if she doesn't have any memories of experiences from that time, then the AD patient is literally not the same person as the person who had those experiences.

Nowadays many philosophers who are inclined toward a Lockean view actually endorse a broader psychological theory, rather than a narrower memory theory, so that what matters are not just connections of memory but rather more general psychological connections. Depending on how far the AD has progressed, however, these other psychological connections may be missing as well.

But as plausible as the psychological theory sounds, it is very hard not to believe that it's still Grandma who is there, afflicted with this disease. After all, we still visit her, we care about how she's treated, we haven't yet held a funeral, her will has not been probated, etc. etc. So we seem to have some conflicting intuitions on this score, intuitions that suggest that something other than psychology might be involved in personal identity. There are other philosophers who argue that bodily continuity is what matters, and yet others who have focussed specifically on the brain (even if the brain does not support the same psychology over tiem). So the whole subject is very tricky indeed.

You may be interested to read John Perry's Dialogue on Personal Identity and Immortality, which is a short and accessible treatment of many issues that will be relevant to your project. Good luck with it!

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