Stardate 20040610.1517

(Captain's log): One mark of superb drama is that it makes you think. It challenges you, it forces you to question, it may confuse or bewilder you. Good drama stays with you, and it may even change you.

After I watched the anime series Serial Experiments Lain, I was filled with ideas and thoughts and ended up writing a long post about the nature of intelligence, in which I explored some aspects of what are known as "hive minds".

A few days ago I watched Ghost in the Shell, an anime movie made in 1995. It is superb; I really enjoyed watching it. And now I find myself full of ideas and thoughts about the nature of identity.

One way to examine your understanding of some concept is via thought experiments. A famous example of a thought experiment is now generally referred to as Schrödinger's Cat. It examined certain aspects of quantum mechanics which were counterintuitive, by fabricating a situation where we might be forced to think of a cat as being simultaneously alive and dead based on one interpretation of quantum mechanics. (That is not the same as saying that we don't know whether it is alive, and that's why the result seemed counterintuitive.)

A different thought experiment forces us to examine the question of when someone or something is a person. We assume that there is consensus that slavery is wrong, and that no person should be permitted to own another person. On the other hand, we assume consensus that there's nothing wrong with ownership of more traditional kinds of property, and likewise nothing wrong with ownership of animals such as dogs and livestock. When it comes to animals, ownership is usually considered to carry certain obligations, but we don't think of dogs as being slaves as such. Equally, we don't think of cars or books as being slaves.

And for the moment we don't think of computers as slaves. But what if we became able to produce computers which were easily able to pass the Turing Test? What if it were possible to produce androids which could pass for human, or come close to it? At what point in the process of development of such units would we have to cease thinking of them as property and start thinking of them as slaves? At what point would we have to consider the possibility that they were entitled to civil rights? What is our real definition of "person", if we don't define persons as members of the species Homo sapiens?

The best thought experiments force us to examine whether we truly understand various categories and properties, by presenting us with cases which straddle the boundaries. By showing us that the boundaries are fuzzy, they show us that our concepts are also fuzzy, and that we don't really fully understand them as well as we presumed we did.

Another concept we don't really fully understand is life. Biology hands us viruses and forces us to consider whether viruses are alive or not. This isn't really a question about the nature of viruses; that's pretty well understood. It rather forces us to examine whether our concept of "life" does or does not apply to viruses. The best answers I've seen boil down to "I don't know". They conclude that we probably cannot formulate a rigorous definition of "life", and without one we can't easily say whether viruses are alive because they straddle the boundary too thoroughly.

Biological study of sponges and jellyfish turns out to force examination of another question: what's the difference between a colony and a single organism with multiple organs? In some jellyfish it isn't easy to say whether certain features are members of a colony or organs of a single creature.

Ghost in the Shell challenged me to consider the question of what I actually am. What makes me what I am?

What am I? That can be answered in many ways. I am a particular human being; I am this body. But is the entire body really part of the essential me? I don't consider myself to be different – or to have died – if I trim my fingernails or get my hair cut. If I suffered a grievous injury and had a limb amputated, I would still be me. If I received a heart transplant, I would still be me. (And the donor of that heart would still be dead.)

We consider quadriplegics and "basket cases" (quadruple amputees) to still be alive and to still be themselves. So that means my first answer isn't correct. I am not this body. I must only be part of it. Then which part? What am I?

These are troubling questions for mechanistic atheists like me. We think of humans as walking fires, as complex biological mechanisms which exhibit properties of life, thought and self consciousness powered by controlled release of chemical energy through oxidation. But close examination of our conception of those properties makes clear that we don't really fully understand any of them. For each we have little difficulty describing paradigmatic cases which we are certain have the property in question, but around that center the boundaries are fuzzy. We do not really know where the boundaries are; we may never really be able to say.

I know that I am alive, but what is the dividing line between life and death? I have a concept of myself as existing, but what is the essential nature of that which makes me what I am?

For believers in certain religions, the answers to these questions are much easier. For Buddhists, for example, the essential self is not an aspec