Our model of the physical world, including brains, is based on our sensory impressions, our experiences. There are objects in the world available to our sensory impressions (organisms -- or more exactly nervous systems or brains), which seem to generate those very sensory impressions. So this brain of mine can be at one and the same time the object of my sensory experience (OK I'm stretching the point here -- but you get the angle, I'm sure) and *generate* that experience. It's kinda tangled isn't it?

And it's certainly true that the physical can't be considered a purely objective phenomena, independent of our subjective consciousness. That has been firmly established by 20th Century science, by the work of Heisenberg and many others. We know the act of observation can change things -- and can do so in the most bizarre and counter-intuitive ways, as various experiments in quantum mechanics show.

Hameroff and people like him think they have found a way through this thicket. Consciousness, they say, arises when an organism "changes things" by chosing which way its internal, isolated quantum states collapse into measured states. (The details don't really matter, except in so far as they help one get a better grasp on the idea, but google on "microtubules" to learn more).

Stuart Hameroff, Roger Penrose, Marvin Minsky and others think that organisms are not mechanical devices, but are *uncomputable*. Or to put it another way, that organisms are underdetermined in their behaviour. What we do next is not completely determined by our history up to the moment -- we have freedom of action in a way that a computer does not.

We have some freedom of action in the world because we make the world up (just a little bit at a time) as we go along. Of course, that's a flat contradiction to the determinism of relativity, but so is quantum mechanics itself, so that's not entirely Hameroff's problem