Doomsday has a long history, almost as long as that of the human race whose extinction it continually foretells. In the early days of the species, when war, disease, and starvation crowded the horizon, the prospect of mass death was real and imminent. With the end of the world forever at hand, pessimistic prophets had no trouble attracting an audience who were eager to discover the kind of moral adjustments needed to stave off the end and achieve spiritual salvation when it finally came.

At this late stage in the 20th century, whatever the recent triumphs of medicine and diplomacy, it is surprising how little has changed. The creation of the atomic bomb may have marked the beginning of new era in doomsdaying, and there is no denying the gloom that’s now in the (increasingly polluted) air. Whether from the torching of the rainforests or the emergence of the Ebola virus, the tinkering of genetic engineers or the threats of political terrorists, human existence seems imperiled at every turn.

It is within this atmosphere of doubt that University of Guelph philosophy professor John Leslie has written his detached and disturbing book on the devolution of our species. The End of the World, subtitled “The Science and Ethics of Human Extinction,” is a difficult and demanding assessment of the chances we have of surviving much longer. Unusual for a work of philosophy, it ranges widely among scientific evidence and treats exploding supernovas and nanotechnology disasters with the same intellectual respect as more strictly philosophical arguments about determinism and ethical values.

Leslie is at his most accessible when he surveys the risks that lie in wait for the human race, ranging from nuclear war and overpopulation to comet strikes and black-hole explosions. The information he has gathered – about false alarms in military detection systems, for example – is detailed and up-to-date, and he brings a philosopher’s skepticism to the bland reassurances of government and corporate apologists. But very quickly, he shifts into murkier realms, accepting the colonization of the solar system as a given and discussing dangers, such as metastable vacuums upset by particle accelerators, that make black holes look crystal clear.

Though Leslie’s style is as open as the subject allows, this is largely an esoteric book that gives over what seems a disproportionate amount of space to a theory of why we are more logically and iminently nearer the end of all human beings than any who have ever lived. Accepting that theory, Leslie believes, will compel us to take his assorted threats of extinction more seriously. But it is not fear of runaway science that is hard to generate among the nervous multitudes so much as understanding. Burning rainforests are so much easier to comprehend. But however opaque the evidence presented here, the arguments are always challenging and command attention.