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Arguing About Extraterrestrial Intelligence

Cowie, Christopher (2023) 'Arguing About Extraterrestrial Intelligence.', Philosophical Quarterly, 73 (1). pp. 64-83.


Avi Loeb has defended the hypothesis that the interstellar object, ‘Oumuamua, detected in 2017, is in fact an extraterrestrial artefact. His hypothesis has been widely rejected by the scientific community. On examination however it is not clear why. The puzzle is at the level of argument structure. The scientific community's responses to Loeb's hypothesis appear to point to explanations of ‘Oumuamua's properties that are mere possibilities. Yet this is something that Loeb does not contest. I appeal to broadly philosophical considerations to understand and bolster the response to Loeb. These considerations concern the structure of his argument, the role of prior confidences within it, and the presence of ‘unconceived alternative’ explanations. I then generalise. ‘Oumuamua will surely not be the last object that does not admit of straightforward natural explanation and that is claimed to be evidence of an extraterrestrial artefact. I use the preceding discussion of Loeb's argument and the scientific community's response to make some general remarks for future debate about similar cases.

Item Type:Article
Full text:Publisher-imposed embargo until 26 March 2024.
(AM) Accepted Manuscript
File format - PDF
Publisher Web site:
Publisher statement:This is a pre-copyedited, author-produced PDF of an article accepted for publication in The Philosophical Quarterly following peer review. The version of record: Christopher Cowie, Arguing About Extraterrestrial Intelligence, The Philosophical Quarterly, Volume 73, Issue 1, January 2023, Pages 64–83, is available online at:
Date accepted:17 February 2022
Date deposited:30 June 2022
Date of first online publication:26 March 2022
Date first made open access:26 March 2024

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