I see occasional references to this claim: Immanuel Kant believed that all the planets in the solar system are inhabited. What's more, that he had a proof! I have carefully checked my dog-eared copy of A Critique of Pure Aliens, but cannot find the claim.

Did Kant believe that? If so, can anyone provide a citation?

  • If Kant was alive now I take he would say that there is life on other planets outside the solar system... Oct 7, 2017 at 9:41

1 Answer 1


Yes he did. He has a whole section on the inhabitants of other planets in a book he published called Universal Natural History and Theory of Heaven (Allgemeine Naturgeschichte und Theorie des Himmels), published in 1755.

Keep in mind that he was an astronomer and that given the level of scientific knowledge of the day (with the still relatively recent discovery of the heliocentric system, limited knowledge of conditions on other planets, limited knowledge on the nature of organic life and oxygen, etc...),that there was no a priori reason to expect that other planets weren't inhabited. And the belief was wide spread among philosophers of the period: Rousseau and Voltaire for example, also believed in extraterrestrials.

  • Was about to answer; specifically it appears in part three, english text here.
    – Not_Here
    Oct 6, 2017 at 4:54

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