What does hope mean anymore? In some ways, it's a meaningless question, for hope is built in -- shaped by our Pleistocene ancestors and their practical hopes -- for instance, that there might be a tasty mastodon around the next corner. Every time you open your email and find a message, it's a hope fulfilled -- the hope that the universe will acknowledge you. Which is why both emails and hope are seductive.

But perhaps you're wondering about the future, that land of dreams and nightmares -- and hope -- that doesn't exist yet. Maybe you were calculating the effects of global warming -- those floods and fires we've been warned about -- and which are now manifesting. Or you're worried about overpopulation: can the planet really sustain 10 billion people? Or pondering the death of the ocean and the bluegreen algae that makes most of the oxygen we breathe. Or you're obsessing over the world financial crisis, or the widening gap between the elite haves and the slave-like have-nots, or the prevalence of cybercrime.

All are cause for concern. But with ingenuity, inventiveness and luck, all stand a chance of being mitigated. But without hope, they don't. Some hopes are groundless, needless to say: gamblers are very hopeful, as are bank robbers. Second marriages, said Oscar Wilde, are the triumph of hope over experience.

But where there is no hope, there is merely grim acceptance, or else despair; and neither of those has ever inspired a new creation, or motivated anyone to dig his way out of a dungeon. What hope means today, however, is what it's always meant: Where there is hope, there's more hope. And, in view of the dire predictions we face, hope is the very least we need to keep going.

Click here for an excerpt from "Erase Me," episode three of Margaret Atwood's Byliner Original series, "Positron." Read more of the series and explore buying options at Byliner.