(1) This chapter looks again at various points made in Chapter 5, considering them with the help of thought experiments. These are designed for discovering whether there are crucial differences between position in space and position in time, particularly in the case of an indeterministic universe.
(2) The chapter also considers the doomsday argument’s ‘reference class’. Could beings of the far future, for instance, be counted as ‘humans’ despite being very different from you and me? Could the argument be applied to all intelligent beings in a series beginning with humans but ending with advanced computers? Thought experiments might once again give us our answers.
As this chapter, 1 like the others, is intended to be readable in isolation, it starts with a brief recapitulation. The doomsday argument, originated by B. Carter and then published and defended by J. Leslie, with variants by J.R. Gott and H.B. Nielsen, points out that you and I would be fairly unremarkable among human observers if the human race were to end shortly: roughly 10 per