Tuesday, May 16, 2006

Part 8: Decisions, decisions

One of the most important questions about consciousness is whether humans have free will. The simplest theory says no - we are all mindless machines, and if we get a large enough microscope and look at the human brain, we will find that the way it works is completely determined by its current state. This view is called determinism and can be summarised in the following sentence. Every event that will happen in the future is completely determined by the sum of all the events that have happened in the past. This applies to all of the choices that we make - determinism says that every decision has already been made and free will is an illusion. If we could make a big enough computer and could understand how neurons send messages, then we could create a simulation of a human brain, and that simulation would be conscious in the same way that a real human is.

The main criticism of determinism is the claim that free will is an illusion. That bothers people. In 1984, Daniel C. Dennett wrote a book entitled Elbow Room: The Varieties of Free Will Worth Wanting. Wikipedia has an excellent summary of it. In the book, Dennett argues that (1) free will is an attribute of intelligence, not consciousness, (2) there is no plausible physical explanation for how free will would work if it existed, (3) free will is an illusion, but a very useful one from the point of view of evolution, and evolution explains why humans are so defensive of the idea of free will.

(1) There is a type of incect called Sphex that feed their young by hunting other insects and bringing the prey to their nest. Before entering the nest, a Sphex drops its prey outside and inspects the next. If there is no danger, it comes out and drags the prey inside. If, however, somebody moves the prey farther away from the nest, the Sphex will find it, drag it back, leave it outside and go inspect the nest again. This can be repeated indefinitely. The insect behaves like a machine. Its brain is not complex enough to recognise the repetitive behaviour and make a different choice. It has no free will. We could define free will as the ability to avoid such futile behaviour. We humans can do it because we are more intelligent than insects. We could make the choice to break the cycle. We could even teach a computer to recognise and avoid this futile behaviour, and computers aren't conscious, are they?

(2) If we do indeed have free will, then where does it come from? The only explanation that philosophers and physicists can come up with is "quantum stuff". Everything else that we know about this world is deterministic, but in quantum mechanics we have probabilities and quantum superpositions. What if our freedom of choice comes from such superpositions, when, say, an electron is in two states simultaneously, and then it collapses into one of those states? Could that be the act of making a decision? Dennett argues that this is silly. How could we possibly have any control over which state the electron goes to? How could we call this freedom? If the electron randomly chooses a state, is that any better than making no decision at all? Would you rather all your decisions were pre-determined or random? Is there any difference?

(3) Finally, Dennett explains why we have (the illusion of) free will with the help of evolution. Free will is not the ability to make decisions; it is the ability to evaluate decisions, and that is a property of our complex brains. We can consider multiple options and choose the best one. Which one we choose is completely determined by our past experiences, but we are still able to choose. We evolved this ability because it is extremely beneficial to our survival. It is the reason that we are the most advanced beings on this planet.

Evolution also explains why we are so opposed to the idea that free will is an illusion. A species that believes it has no choice in life is likely to get depressed and apathetic, and that leads to death.

So what about responsibility? If I have no choice in any of my decisions, why should I bother making them? Why should I try to make the right one? The answer is that responsibility leads to good decisions. The reason we have laws is because they are beneficial to society as a whole. And the reason we choose not to kill or steal is because we know the consequences of those actions. The presence of responsibility affects the way in which we evaluate our decisions.

So why not give up and stop living? Nothing we do matters anyway. It is all pre-determined. Well, that is a choice you have. You have the ability to consider that choice. But realise that, as humans, we have the freedom to make the best decisions! Animals and computers and very bad at evaluating options and picking the best choices. You are much better at it. So why not take full advantage of that amazing ability?