Even though the outside world has not changed, your brain dynamically presents different interpretations.

The deep secret of the brain is that not only the spinal cord but the entire central nervous system works this way: internally generated activity is modulated by sensory input. In this view, the difference between being awake and being asleep is merely that the data coming in from the eyes anchors the perception.

As Carl Jung put it, "In each of us there is another whom we do not know." As Pink Floyd sang, "There's someone in my head, but it's not me."

None of the individual metal hunks of an airplane have the property of flight, but when they are attached together in the right way, the result takes to the air. A thin metal bar won't do you much good if you're trying to control a jaguar, but several of them in parallel have the property of containment. The concept of emergent properties means that something new can be introduced that is not inherent in any of the parts.

The drives you take for granted ("I'm a hetero/homosexual," "I'm attracted to children/adults," "I'm aggressive/not aggressive," and so on) depend on the intricate details of your neural machinery.

Who we can be begins with our molecular blueprints - a series of alien codes penned in invisibly small strings of acids - well before we have anything to do with it. We are a product of our inaccessible, microscopic history.

We don't really understand most of what's happening in the cosmos. Is there any afterlife? Who knows.