Four things do not come back: the spoken word, the sped arrow, the past life, and the neglected opportunity.

Similarly, knowledge of the future was incompatible with free will. What made it possible for me to exercise freedom of choice also made it impossible for me to know the future. Conversely, now that I know the future, I would never act contrary to that future, including telling others what I know: those who know the future don't talk about it. Those who've read the Book of Ages never admit to it.

Physics admits of a lovely unification, not just at the level of fundamental forces, but when considering its extent and implications. Classifications like "optics" or "thermodynamics" are just straitjackets, preventing physicists from seeing countless intersections.

It is a misconception to think that during evolution humans sacrificed physical skill in exchange for intelligence: wielding one's body is a mental activity.

Four things do not come back: the spoken word, the sped arrow, the past life, and the neglected opportunity.

Science fiction is very well suited to asking philosophical questions; questions about the nature of reality, what it means to be human, how do we know the things that we think we know.

Brain damage is never a good idea, no matter what your friends say.