Why I asked this question : https://gallica.bnf.fr/ark:/12148/bpt6k90195m/f54.image
p 50-51, in course of Cauchy, a proof of the intermediate value theorem. Now, that's not a proof.
And I learned that Cauchy had made a lot of mistakes, so this is not a proof, of a change of standard between our era and that of Cauchy.
But the question stay : has the standard of mathematical proofs changed over time ?