As its title (with no question mark) implies, this is a rather pessimistic book. You might expect the Astronomer Royal to talk about astronomical hazards such as asteroid impact and indeed he does, pointing out that the risk of an individual dying through such an event is similar to the risk of dying in an air crash. He looks back historically at the great risk we ran of annihilation by nuclear war particularly during the Cuban missile crisis of 1962. Kennedy and Krushchev were leaders of restraint and sobriety, but we had to be lucky as well as wise to survive. Now the risks are more diverse, arising from runaway technology, environmental catastrophe, extreme irrationality, and terrorism. Rees hopes that catastrophes will not happen, but he has made a thousand dollar bet "that by the year 2020 an instance of bioerror or bioterror will have killed a million people." Can we slow science down by restricting dangerous technologies? Of course we do this at present by imposing limits on exposure to radiation, by controls on biological experiments etc., but we cannot always predict the effects of our activities and controls are not always effective.
The "doomsday philosophers" argue from quite general principles, independent of any environmental considerations, that the world population is unlikely to continue at its present level for many more generations. Are these arguments convincing? Rees cannot pinpoint the flaw, but recalls George Orwell's comment "You must be a real intellectual to believe that no ordinary person could be so foolish."
Rees believes that the scientific enterprise is unending and that the fundamental nature of our cosmos may never be understood the task may be beyond the capabilities of the human mind. He suggests that "we know too little about how life began, and how it evolves, to be able to say whether alien intelligence is likely or not." If the cosmos is already teeming with life, "nothing that happens on Earth would make much difference to life's long-range cosmic future", but if "Earth is the unique abode of intelligence in our entire Galaxy our fate would then have truly cosmic resonance."
In the last paragraph of the book Rees gives his opinion "that humanity is more at risk than at any earlier phase in its history. The wider cosmos has a potential future that could even be infinite. But will these vast expanses of time be filled with life, or as empty as the Earth's first sterile seas? The choice may depend on us, this century."
I believe in humanity. We are an incredible species. We're still just a child creature, we're still being nasty to each other. And all children go through those phases. We're growing up, we're moving into adolescence now. When we grow up - man, we're going to be something!