Well, it had to come to this in the end. The eternal problem of what happens when you cut your brain in half! No really, this is serious. The split-brain problem is one of the most perplexing known to Man, and it’s study has helped many people, including me, understand what it is to be human and, most intriguingly, where our “soul” may lie.
Derek Parfit’s book Reasons And Persons took me so far in my thoughts that I eventually stopped; having read enough and thought enough to satisfy a lifetime’s desire for this kind of thought. The difficult and complex web of ideas that Parfit weaves took so long to truly understand (for me, anyhow) that I had time to change my mind numerous times.
This thought, written in February 2004 gives some sense of where I had been:
We go through life thinking that we are special, that we have some divine property that distinguishes us from the rest of the animal kingdom, and from all other humans. This affects our awareness of who we are, generating a spectrum of beliefs from us actually being separate from our physical self through to some vague awareness that we cannot just be a collection of thoughts – there must be more to consciousness than firing neurons.
My own beliefs hovered around the latter end of the spectrum, and I still feel uncomfortable venturing off the edge of the egotistical world into the world of the reductionist (we are just a bit of meat!). Nevertheless, analysing the possible nature of our self, identity, ego, call it what you will, has produced a range of ideas that culminate in a “multiple personality model”. In this, one personality (a.k.a. self) is dominant under normal situations, whereas all other personalities, be they potential or real, are supressed by the brain, thus allowing us to function as a single identity.
The difficulty comes when we divide the brain into two halves, and accept that we cannot unilaterally exist in two bodies / jars in the lab, at once. The multiple personality model allows an additional self to be unsuppressed in the “selfless” part of the divided brain, probably with the same set of memories, although in a different body (or lack of) and a rather cauterised brain. This sounds comforting if you believe that we must exist as something more than just thoughts.
When you look at the nature of this “something more” in all its possible forms, however, then it only has two components:
1) The accumulation of all of our memories.
2) The awareness and control of our physical being and its surroundings.
Our entire identity is produced by the interaction of these two components and nothing more. We are such stuff as meals are made of.
As an example, and probably the most complex of all, when we fall in love we recognise the potential compatibility and joy we may have with another individual (based on 1 & 2), our body produces hormones and imposes physical changes that make us feel love (2) which is combined with past experiences of a similar nature (1). Our loyalty to that person is the result of knowing what we will experience both if we are not with them and if we are (1), and when they whisper sweet nothings in our ear, our auditory system sends messages (2) to our brain which triggers both a sense of physical well being (2) and further good memories (1).
This may be a very crude analysis of such a complex and highly regarded emotion, but it does make clear that given a different, but identical, body, environment and memories, we would experience precisely the same emotion, and be none the wiser about who we may or may not be. Unfortunately for the reductionists, it still takes a giant leap of faith for anyone else to believe this; something that most people are far from willing to take, or may even be capable of taking.
The fact that I was able to distance myself totally from possibly the most intense emotion that we can ever experience, gives some idea of how distanced I had become from my own emotions. That sparse place is not a place anyone would truly want to remain; but as sparse as it is, it is the place you have to go if you are to make your mind up, in a truly objective way, what it is you want from life, and how you feel about yourself.
Soon afterwards I felt the need to tie up all the loose ends, and deal with things in a more humane manner; a sort of denouement for the soul. There is nothing apparently startling in this last piece, but it closed the loop for me – made me realise that I had finished my journey and had far more important things to get on with. Like trying to make this planet a place worth living in.
I have written before of our identity being formed solely of our memories and the way in which we interact with and sense our environment. I believe that this is the essence of being, but it does not fully address the issue of continuity.
Non-reductionists and reductionists alike accept that there is a thread of consciousness running through our identities, the difference between the two types of belief is the nature of this consciousness. A reductionist believes only that consciousness is inherent in our brain (and body to a lesser extent), non-reductionists believe that there is something more than this.
The most intractable problem we face is what happens to this consciousness to ensure that we continue from day to day as the same person. The Cartesian belief makes this simple : it doesn’t matter what happens to our physical self, there is a separate entity which is distinct from anything tangible. Parfit, and others do not accept the separate entity, but allow for the loss of any physical entity providing that psychological continuity exists, i.e. our memories remain intact. Similar in many ways, but also distinct, Nagel is of the opinion that the brain is necessary to ensure continuity.
Let’s suppose that when we sleep, our memories (for which read the specific states of all the neurons in our brains) are transferred to another person. Our brain, that which we inhabited prior to sleep, is destroyed. Do we wake up in the brain / body of the other person?
Well, for a start, in order to transfer these memories to another person, we have to fundamentally change the state of many, if not all, neurons in that person’s brain. This will effectively, on most views, destroy the continuity of that person. But do they become us?
At first glance the answer would seem to be yes, our mental state has been transferred, so we are bound to wake up in the other brain / body.
But what happens if our original brain is not destroyed – would there be two of us? And if so, could we be simultaneously aware of waking up in both of these people. The answer lies in the meaning of the term “us”.
Parfit would say that this meaning does not matter, providing that x number of identical (or very similar) sets of mental states exist somewhere. It is comforting to some of us to believe this point of view; we do continue, even if the thing we call “us” has been discontinued. Our legacy lives on in what we do, and have done, and what we are able to express. If we do good, then in two bodies surely we can do twice as much good.
But to many people, including Parfit, it does matter at some levels what happens to “us”.
Awareness, identity, self, whatever you call it, tends to have a special meaning for most people, beyond just physical states. If we are to understand the concept of “us” then we need to understand what it is that goes beyond these physical states.
Most people understand that when we sleep our awareness of our external and internal environment switches off. Various “subconscious” systems related to sense still operate, such as that which wakes you upon hearing a loud noise, but by most definitions you are unaware when you are asleep. When you wake up you are again aware of your environment; so what has changed between being asleep and awake? The clue may lie in these subconscious systems.
It is tempting to think that the systems that are still operating whilst asleep provide us with a level of continuity, bridging the gap between awake (aware) and awake again. However, these systems do not actually provide us with what most of us would consider “conscious awareness”. When we fall asleep, we are not aware of anything until we wake up again (note : “dreaming” is the conscious awareness of thoughts generated whilst asleep, and continuing into wakefulness – night-dreams that we are aware of are no different to any other thoughts in conscious terms). When we wake up, we are once again “us”; we have continued.
The comatose mind provides some useful extra information; we are still “us” when we are no longer comatose, assuming we have not changed greatly. If we have changed greatly, due to loss of memory or physical degradation, then we may be considered to no longer be “us”. Parfit provides a resolution here; the question of “how much do we have to change to no longer be us?” is an empty question – we can never know the answer because we cannot be objective in our definitions. This case shows that even if the person who comes out of a coma is fully conscious of their environment, they may have changed significantly enough to consider themselves to no longer be the same person. “Us” has not continued for them, even though we may consider (or wish!) them to be the same person
The final piece of information must be to define what is meant by “conscious”. If we lack consciousness in its true sense, i.e. not just being awake, then we cannot be said to be “us” any more. This is the kind of situation that even Parfit fears.
In simple terms, consciousness is the awareness of our external and internal (body) environment and the ability to convey that awareness in some way. Igor Aleksander provides 7 principles of consciousness that must be present for consciousness, but I believe that we have to be flexible in our definition. Just because we do not know that someone is conscious, doesn’t mean that they are not. For the sake of this argument then let’s allow consciousness to actually mean “provable” consciousness, i.e. a person passes all of Aleksander’s 7 principles, but allowing for the fact that in reality there may be no way of actually proving this.
Given this information, here is a suggested definition of mental continuity:
The facility for a conscious being to retain a defined proportion of their previous memories, within a defined proportion of their previous physical self.
This is a vague definition, but then it is a very vague concept. If you wake up in the same body, with the same brain, but cannot remember your name, age, partner’s name or where you were born, then you could be considered as no longer you. The same could be said if you wake up with half of your face missing; but the difference is that we, as a species, give much more importance to our mental self than our physical self when defining “us”. A kangaroo would probably not be considered the same kangaroo if it lost its legs, even if it still remembered everything; its just that kangaroos legs are far more important to survival than ours.
In the end, whether we are still â€œusâ€ only matters in the sense that we are able to do and think the way that we previously did. Viewed from the outside or the inside, what we really care about is change, and some people fear change more than others.