The rally, or the last hurrah, which in recent years has been termed terminal lucidity, refers to where a person, typically suffering from dementia or some other neurological disorder, suddenly and seemingly miraculously reverts to their pre-dementia original selves. This usually occurs shortly before death. I recently read a book on this topic called Threshold: Terminal lucidity and the Border between Life and Death by Alexander Batthyány. I'll provide a summary of the salient points of this book followed by a few of my thoughts.
A summary of the book
According to Alexander Batthyány, states of intoxication and other induced exceptional psychological states pose a relatively weak argument against an enduring self or soul. This is for the simple reason that such conditions are temporary, and the original self soon returns. So, here, it cannot be the case that the original self was ever destroyed. The original self was there all along, but temporarily hidden.
It is seemingly very different with dementia. The progression of dementia appears to actually destroy a person's beliefs, interests, memories, and very character. This, in turn, also implies that normal brains cause our usual standard personality and character. If these suppositions are correct, what can be left of any eternal, immutable soul?
However, terminal lucidity has now demonstrated that the original self can return. This is, to say the least, perplexing since, at least with dementia, the damage to the brain is still there. How is it possible to have a normal, clear, lucid mind with a severely diseased brain if the brain produces consciousness? Indeed, it doesn't seem possible.
The author draws parallels between terminal lucidity and Near-Death Experiences (NDEs). In NDEs, we also have self-consciousness and personhood when these ought to be highly unlikely given the impaired brain states. So despite compromised brain activity during both terminal lucidity and NDEs, individuals have normal if not enhanced mental alertness, vision, and memories. As an aside, whilst the author doesn't mention this, one might wonder about a potential connection to savant syndrome here?
The author posits that both terminal lucidity and NDE's strongly imply that it cannot be the brain, or indeed the whole body, that somehow produces consciousness. And yet, on the other hand, the author also feels this is strongly contradicted by all the other overwhelming evidence that appears to show that consciousness, or the mind, is very much dependent on the proper functioning of one's brain.
The author tries to reconcile what terminal lucidity and NDE's seem to imply with this contrary evidence, by employing two analogies. The first one is that the mind-brain relationship resembles a total solar eclipse. During such an eclipse, we cannot see the sun, we can only see the coronal filaments peeping out from behind the moon. If we did not know better, we would fallaciously infer the moon somehow produces these filaments. Similarly, we fallaciously infer the brain produces consciousness. The other analogy is the mind at large idea. This holds that the brain functions similarly to a “reducing valve”, which filters out a much greater and expanded consciousness to prevent us from being overwhelmed and confused by a vast ocean of conscious experiences.
On the other hand, apparently contradicting this evidence is the undeniable fact that a damaged brain usually leads to a damaged mind. Do the total solar eclipse and the mind at large analogies explain how a soul could exist in the face of all this contrary evidence?
[W]e would expect the progressive destruction of more and more of the brain’s “filter” by Alzheimer’s disease to progressively “free” more and more of consciousness, and thus increase Alzheimer’s patients’ mental proficiency as the disease progresses.
Of course, with terminal lucidity, some Alzheimer’s patients' mental proficiency is indeed increased (which they do not mention), but this is the exception rather than the norm. So the mind at large hypothesis needs to be fleshed out a bit to address this criticism.