Francis Collins

The brain is the most complicated organ in the universe. We have learned a lot about other human organs. We know how the heart pumps and how the kidney does what it does. To a certain degree, we have read the letters of the human genome. But the brain has 100 billion neurons. Each one of those has about 10,000 connections.

If you are looking for a needle in a haystack, and somebody has already cataloged all the straw in the haystack, when you get to that needle you will recognize it's different than what was supposed to be there based on all that computerized haystack information that had been predetermined for you.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.