For pure joy, I look at a small painting by Arbit Blatas. An ocean liner is at the center of the composition, perhaps ready to depart. It holds the promise of discovery.

There are ways in which you can make that distinction objective to a certain degree. For example, by looking at responses that could be generated in the brain to exactly the same stimulus and there could be differences there.

You can be highly concentrated on a person, on a problem, and be so good at excluding all other material that that becomes not just the focus of your experience, but practically the sole content of your experience, everything else falling by the wayside.

Consciousness permits us to develop the instruments of culture - morality and justice, religion, art, economics and politics, science and technology. Those instruments allow us some measure of freedom in the confrontation with nature.

How can you have this reference point, this stability, that is required to maintain the continuity of selves day after day?

When you deal with something like compassion for physical pain, which we know is very, very old in evolution - we can find evidence for it in nonhuman species - the brain processes it at a faster speed. Compassion for mental pain took many seconds longer.

Emotions are enmeshed in the neural networks of reason.