This chapter makes a rough attempt to say which are the most dangerous threats to the human race. It also identifies general arguments that are relevant to evaluating the threats: for instance, arguments about whether the world is deterministic, which can be important to the force of Carter’s doomsday argument. Despite the importance of Carter’s point, the chance of Doom Soon may be only about 30 per cent.
Analysing risks is a discipline with a large literature, including the journal Risk Analysis: for a quick introduction see M.G. Morgan’s ‘Risk analysis and management’. 1 So far, though, the field’s complexities have made it only rather poorly developed. The fact that smoking puts you in grave danger of cancer and other diseases was doubted for quite some time by statisticians, yet the latest findings from a forty-year study of British doctors indicate that one smoker in two will die from the habit, a proportion much higher than previously believed. Again, it has recently been discovered that the strengths of many links between causal agents and risked disasters have been systematically underestimated. Suppose you want to know, for example, what increased risk of heart attack follows from your high blood pressure. Well, those whose blood pressure is usually high may have it measured when it is low, and vice versa. Taking proper account of this, one finds that high blood pressure is 60 per cent more of a risk factor than had been thought.
When such intensively studied medical risks, involving events repeated in the lives of vast numbers of people, are so hard to measure, it clearly won’t be easy to get a trustworthy figure for