Serbian Astronomical Journal 2003 Issue 166, Pages: 1-11
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Extraterrestrial intelligence and doomsday: A critical assessment of the no-outsider requirement

Ćirković Milan M., Milošević-Zdjelar V.

The so-called Doomsday Argument has attracted a lot of attention in recent years. One of the suggested ways to make this argument ineffective is the so-called No-Outsider requirement, indicating that the presence of other intelligent observers (’aliens’) beside humans invalidates the reasoning leading to the apocalyptic conclusion. Obviously, this argumentation bears relevance not only to the effectiveness of the Doomsday Argument, but also to the issues like the relativization of the reference class in anthropic reasoning, transhumanism and the SETI theory. Hereby we critically investigate the No-Outsider Requirement and conclude that it is either fallacious or irrelevant.

Keywords: extraterrestrial intelligence, history and philosophy of astronomy