Talk:Pierre de Fermat
"This margin" is a mistranslation which has unfortunately been propagated into print. A while ago I attempted to correct it in Wikipedia but it was re-edited with a reference to the same very common mistranslation. Although the error is somewhat trivial this set me wondering how someone who actually knows Latin can convince an editor who does not that the published translations are actually wrong.
"This margin" is a misunderstanding of the words "hanc marginis". "Hanc" means "this" and "marginis" means margin but "hanc" is accusative case and "marginis" is genitive so "hanc" cannot possibly qualify "marginis". "This margin" would need to be either "hanc marginem" (accusative) or "huius marginis" (genitive).
"Hanc" actually qualifies "demonstrationem mirabilem", also accusative. "Marginis" actually goes with "exiguitas".
A more accurate translation would be, "I have uncovered a truly remarkable proof but the smallness of the margin would not contain it." Here "hanc" is translated as "this".
More freely: "I have uncovered a truly remarkable proof but the margin is too small for it."
As I wrote earlier it is a fairly trivial point but any translation containing "this margin" is a schoolboy error.