Steven Den Beste's encounter with the Ghost in the Shell movie inspired a discussion about the definition of the self. Pixy Misa had something to say about it as well.
The main problem I had with Den Beste's essay was his insistence on locating the self within the "frontal lobes". We're not brains in boxes, and to define the self as the brain, or even the mind, is to insist on an overly rationalistic conception of oneself. We don't have a strong particular attachment to that fingernail, or that hair, that flake of skin, or even that pinkie lost in a biking accident when we were six. But they were all still part of the self, however infinitesimal.
The mind extends itself to the fullest extent of the self, and it doesn't even limit itself to the physical body. I extend beyond my skin. When I drive, I am in a certain sense the car; once, when I lost control of my old Ford Escort on Route 22 in a slushstorm, the disorientation and shock was tangible, physical, real - even though nothing happened to my body, let alone my brain. I happen to have an unusually overdeveloped sense of personal space - as much as two feet in some situations. It's actively uncomfortable to have someone I don't have a sense of intimacy with, invade that space. This is why I hate going to see movies I know will be showing in a full house - because I don't like that sense of unwanted intimacy with strangers.
But this means, I think, that the self is not an indivisible whole, an atomized, singular essence. When I park my car, turn the engine off, and get out, I am no longer that man-in-a-sedan self. I discard that part from my self, and become a biped again. Our things are temporary extensions of ourselves; how important those extensions become is entirely dependant on how much emotional importance we invest in those elements of the self. Possession-proud people invest great portions of their personalities, themselves, into their things, their stuff. Land-proud folk invest themselves into their land; such people once evicted are no longer the same people they once were.
Body-proud people, of course, are most invested in their physicalities, that part of themselves which lies within the skin, the muscle and bone, the athletic whole. Those body-proud folk, of course, are most aware of this extension of the self. There is nothing quite like exertion to remind oneself that one is, of course, something more than an intellect - the loss of breath, the heat, the strain, the adrenaline rush, the trembling, quivering self that twitches and shudders. Ask someone who has just smashed his thumb with a hammer, about the physicality of the self. But be sure to stand out of hammer-range.
And, of course, the dismembered are less for their losses. A hand is not the self, but it is a part of the self. You will not find an amputee at the moment of his or her loss, who will tell you that they don't feel reduced by the loss. Of course, it isn't that simple. The amputee will often *feel* that hand, as if it was still there - ghost sensation, ghost pain, a ghost limb. The brain-in-a-box people will insist that all I've been talking about, the extensions of the self through the physical, is all a mistaken understanding, that the constructed self is built, like the homunculus, a tiny, totally representative model contained wholly within the brain. But I would said that that it isn't simply a map, or a model. It is that part of the world which is made, within the perception, the self. It is constantly informed by sensation and imagination. The ghost-hand is the model deprived of sensation, that part of the self divorced from the world that nourishes it. As that part of the self's experience of the world recedes, it atrophies and fades. That part of the self collapses into sense-memory, then mere remembrance, then nothingness. The self, that part of the self is lost.
Alzheimer's is such a foul disease because it is a leprosy of the self. It rots the self from the remembrance outwards, divorcing imagination from association and association from sense-memory and sense-memory from sensation.