Indeed, the line between perceiving and hallucinating is not as crisp as we like to think. In a sense, when we look at the world, we are hallucinating all the time. One could almost regard perception as the act of choosing the one hallucination that best fits the incoming data.

Remember that politics, colonialism, imperialism and war also originate in the human brain.

Our ability to perceive the world around us seems so effortless that we tend to take it for granted.

We are not angels, we are merely sophisticated apes. Yet we feel like angels trapped inside the bodies of beasts, craving transcendence and all the time trying to spread our wings and fly off, and it's really a very odd predicament to be in, if you think about it.

Yet as human beings we have to accept-with humility-that the question of ultimate origins will always remain with us, no matter how deeply we understand the brain and the cosmos that it creates.

Even though its common knowledge these days, it never ceases to amaze me that all the richness of our mental life - all our feelings, our emotions, our thoughts, our ambitions, our love life, our religious sentiments and even what each of us regards us his own intimate private self - is simply the activity of these little specks of jelly in your head, in your brain. There is nothing else.

One of the first things we teach medical students is to listen to the patient by taking a careful medical history. Ninety percent of the time, you can arrive at an uncannily accurate diagnosis by paying close attention, using physical examination and sophisticated lab test to confirm your hunch (and to increase the bill to the insurance company).