Is it better to say argumentum a/ab contrario or e/ex contrario?

It seems that both are acceptable but in most Romance languages it is a contrario.

The movement out/from is not clear/explicit/graphic and it is a concept/mental abstraction that "moves", not a physical object.

EDIT secondary questions following up to clarify as suggested Why ex and not ab? Why do most Romance Languages have a contrario instead? How did ex contrario evolve to a contrario?

1 Answer 1


This is just a follow-up post to Sebastian's answer, which is correct for Classical Latin. It could be useful to add that the expression a contrario (often used as part of argumentum a contrario) comes from scholastic Latin. The expression a contrario is typically used in Romance-speaking countries, in English-speaking countries, in Slavic-speaking countries, etc. In contrast, the classical form is more typically found in German-speaking countries, in Scandinavian countries, etc. As for OP's question ("How did ex contrario evolve to a contrario?"), I think it is not a matter of "evolution" (?) but rather of "replacement" of e(x) 'out of, from' by a(b) 'from' in this expression. As for the question why such a substitution did not (typically) take place in, let's say, Sebastian's or Joonas's countries (Germany and Finland, respectively; cf. supra), I don't know.

  • 1
    Actually, I would say my answer was just plain wrong, because I had simply overlooked the word argumentum in the question. I have deleted it. Aug 12, 2021 at 18:09
  • Just so this answer does not look completely out of context to readers who cannot see my deleted answer (that takes a certain reputation, I believe), I wrote that only ex contrario is correct. That is the case for the classical expression e/ex contrario which means "on the contrary." But an argumentum e/a contrario is something completely different. Aug 12, 2021 at 19:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.