How many combinations of unintended consequences and human reactions to them does it take to detour us into a future that seems to defy any obvious trend? Not many. That’s why predicting the future accurately is so difficult. Some of the most mistaken predictions I’ve seen are of the straight-line variety–that’s the kind that ignores the inevitability of unintended consequences, ignores our often less-than-logical reactions to them, and says simply, “In the future, we will have more and more of whatever’s holding our attention right now.” [...] So why try to predict the future at all if it’s so difficult, so nearly impossible? Because making predictions is one way to give warning when we see ourselves drifting in dangerous directions. Because prediction is a useful way of pointing out safer, wiser courses. Because, most of all, our tomorrow is the child of our today. Through thought and deed, we exert a great deal of influence over this child, even though we can’t control it absolutely. Best to think about it, though. Best to try to shape it into something good. Best to do that for any child.

Asimov’s favorite of his short stories, and widely regarded to have an astonishing ending.