Euclid vs Eratosthenes
Eratosthenes lived around -200 (more precisely -276 to -195/194) and was a correspondent of Archimedes. Archimedes communicated his Method to Eratosthenes in the form of a letter. Euclid lived around -300. He would have had to enjoy extraordinary longevity to coincide with Eratosthenes.
C.K. Raju goes to some length to argue that Euclid did not exist at all, in Good-Bye Euclid!
He starts from the established fact that, while Euclid was first mentioned by the 5th century philosopher Proclus, our sources for Proclus are a translation from Arabic made in Toledo around the year 1000. Raju has a political agenda for wishing to debunk Euclid, to which I do not subscribe, but some of his arguments are intriguing:
Possibly, the name "Euclid" was inspired by a translation error made at Toledo regarding the term uclides which has been rendered by some Arabic authors as ucli (key) + des (direction, space). So, uclides, meaning “the key to geometry”, was possibly misinterpreted as a Greek name Euclides.
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In attributing the Elements to an early Greek called Euclid, we are supposing that there was a fixed text which was repeatedly copied out without any significant change by subsequent scribes. But the available papyri on geometry from Alexandria do not correspond to the received text, and do not show any such evidence of the existence of a fixed, early text.
Mikhail Katz pointed me, via a MSE thread, to a review by José Ferreirós on Raju's book, since it's behind a paywall I quote the relevant paragraph:
In his interest to revise traditional historiography and oppose proof-centred mathematics, Raju devotes a lot of effort to questioning the existence of Euclid and insisting that the text of the Elements originates at the earliest in 370 CE (with Theon) or perhaps even in the tenth century. In my opinion, this is useless and does not help advance the author’s main theses. For historical purposes, what is relevant is that Elements represents a systematisation of a large portion of geometrical knowledge in the Greek-speaking world before the common era. (‘Euclid’ is simply the name of its otherwise unknown author, whose dates—it is true—are dubious; incidentally, an interesting question would be whether philologists find reason to think that the text of Elements was written by different authors.) Raju insists on the idea that Proclus’s views represent the original philosophy of mathematics in the Elements (p. 25), and he overemphasizes the connections between geometrical proof, Platonism, and Christian religion (see below).