DOOMSDAY!
The Doomsday argument concerns a question sure to arouse interest—the survival of the human race. It is rivaled only by the Simulation argument in attempting to address profound questions of human nature and destiny through elementary probability calculat
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DOOMSDAY!
The Doomsday argument concerns a question sure to arouse interest—the survival of the human race. It is rivaled only by the Simulation argument in attempting to address profound questions of human nature and destiny through elementary probability calculations. Proponents of the argument maintain that we are randomly selected from among all who ever live. This randomness makes it unlikely that we are among the earliest humans. A calculation demonstrates that if we are not among the earliest humans, then the human race has less time left than is usually allotted to it. Among all people who have ever lived, our current birthorder rank is something like 60 billion. If humanity is to continue as long as we usually suppose with the population sizes of the modern world,1 then we shall have a quite low rank among all who ever live. This should be considered unlikely; it is more probable that we have an average rank among all who ever live, in which case doomsday will be much sooner than we generally suppose. Your birth rank (one plus the number of humans born before you) which can be estimated, corresponds to the number on the lottery ticket drawn (see 1.1). This rank is used to infer whether you are part of a big lottery (prolonged existence of the human race) or a small lottery (early doom). This suggests that the entire human lottery is not large relative to our rank, i.e., doomsday is likely to be relatively soon. The ease with which the Doomsday argument extracts from a quite modest investment of current fact, substantial information about the remote future has provoked suspicion in most quarters; however, critiques that have not been snidely dismissive have tended to be as mystifying as the Doomsday argument itself. The Doomsday argument is a worthy paradox in that it is much easier to see the conclusion is unwarranted than to locate the fallacy. Bostrom (2002, p. 109) reports having heard more than one hundred attempted refutations of the Doomsday argument. The Babel of conflicting objections indirectly lends credence to the argument—more than a hundred attacks and still standing. 1
It is the number of future individuals, not the amount of time to Doomsday, that allegedly regulates the sampling probabilities. Although we’ve had a fairly long history with low populations, the Doomsday argument indicates that assuming large populations, we have a short future.
W. Eckhardt, Paradoxes in Probability Theory, SpringerBriefs in Philosophy, DOI: 10.1007/978-94-007-5140-8_2, Ó The Author(s) 2013
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2 DOOMSDAY!
Proponents of the Doomsday argument base their reasoning on Bayes’ Theorem, an uncontroversial proposition of probability theory (see 9.1). Use of Bayes’ theorem should not be confused with Bayesianism, a controversial viewpoint on the nature of probability associated with subjectivism and the claim that correct statistical inference depends crucially on assessment of prior distributions. The most avid frequentist has no quarrel with Bayes’ Theorem proper. Leslie blurs this distinction in a manner th
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