Critias' rendition of Atlantis in Timaeus and Critias
In Plato's myth, Poseidon fell in love with Cleito, the daughter of Evenor and Leucippe, who bore him five pairs of male twins. The eldest of these, Atlas, was made rightful king of the entire island and the ocean (called the Atlantic Ocean in his honor), and was given the mountain of his birth and the surrounding area as his fiefdom. Atlas's twin Gadeirus, or Eumelus in Greek, was given the extremity of the island towards the pillars of Hercules. The other four pairs of twins—Ampheres and Evaemon, Mneseus and Autochthon, Elasippus and Mestor, and Azaes and Diaprepes—were also given "rule over many men, and a large territory."
Poseidon carved the mountain where his love dwelt into a palace and enclosed it with three circular moats of increasing width, varying from one to three stadia and separated by rings of land proportional in size. The Atlanteans then built bridges northward from the mountain, making a route to the rest of the island. They dug a great canal to the sea, and alongside the bridges carved tunnels into the rings of rock so that ships could pass into the city around the mountain; they carved docks from the rock walls of the moats. Every passage to the city was guarded by gates and towers, and a wall surrounded each of the city's rings. The walls were constructed of red, white and black rock quarried from the moats, and were covered with brass, tin and the precious metal orichalcum, respectively.
Athens defeats the Atlantean slave empire which is engulfed by a flood
According to Critias, 9,000 years before his lifetime a war took place between those outside the Pillars of Hercules at the Strait of Gibraltar and those who dwelt within them. The Atlanteans had conquered the parts of Libya within the Pillars of Hercules as far as Egypt and the European continent as far as Tyrrhenia, and subjected its people to slavery. The Athenians led an alliance of resistors against the Atlantean empire, and as the alliance disintegrated, prevailed alone against the empire, liberating the occupied lands.
But at a later time there occurred portentous earthquakes and floods, and one grievous day and night befell them, when the whole body of your warriors was swallowed up by the earth, and the island of Atlantis in like manner was swallowed up by the sea and vanished; wherefore also the ocean at that spot has now become impassable and unsearchable, being blocked up by the shoal mud which the island created as it settled down. 9.^ Critias 116bc
10.^ Timaeus 25c–d, Bury translation
John V Luce (1978). "The Literary Perspective". In Edwin S. Ramage. Atlantis, Fact or Fiction?. Indiana University Press. p. 72. ISBN 0-253-10482-3
Rudberg 1917/2012 ref 13
The logographer Hellanicus of Lesbos wrote an earlier work titled Atlantis, of which only a few fragments survive. Hellanicus' work appears to have been a genealogical one concerning the daughters of Atlas (Ἀτλαντὶς in Greek means "of Atlas"), but some authors have suggested a possible connection with Plato's island. John V. Luce notes that when he writes about the genealogy of Atlantis's kings, Plato writes in the same style as Hellanicus and suggests a similarity between a fragment of Hellanicus's work and an account in the Critias. Robert Castleden suggests Plato may have borrowed his title from Hellanicus, and that Hellanicus may have based his work on an earlier work on Atlantis.
Gunnar Rudberg suggested that Plato's try to realize his political ideas in the city of Syracuse, Sicily could have heavily inspired the Atlantis account.
Some ancient writers viewed Atlantis as fiction while others believed it was real. The philosopher Crantor, a student of Plato's student Xenocrates, is often cited as an example of a writer who thought the story to be historical fact. His work, a commentary on Plato's Timaeus, is lost, but Proclus, a Neoplatonist of the 5th century AD, reports on it. The passage in question has been represented in the modern literature either as claiming that Crantor actually visited Egypt, had conversations with priests, and saw hieroglyphs confirming the story or as claiming that he learned about them from other visitors to Egypt. Proclus wrote:
15 Timaeus 24a: τὰ γράμματα λαβόντες.
16.^ Cameron 2002
17.^ Castleden 2001, p,168
As for the whole of this account of the Atlanteans, some say that it is unadorned history, such as Crantor, the first commentator on Plato. Crantor also says that Plato's contemporaries used to criticize him jokingly for not being the inventor of his Republic but copying the institutions of the Egyptians. Plato took these critics seriously enough to assign to the Egyptians this story about the Athenians and Atlanteans, so as to make them say that the Athenians really once lived according to that system.
The next sentence is often translated "Crantor adds, that this is testified by the prophets of the Egyptians, who assert that these particulars [which are narrated by Plato] are written on pillars which are still preserved." But in the original, the sentence starts not with the name Crantor but with the ambiguous He, and whether this referred to Crantor or to Plato is the subject of considerable debate. Proponents of both Atlantis as a myth and Atlantis as history have argued that the word refers to Crantor.
Alan Cameron argues that it should be interpreted as referring to Plato, and that when Proclus writes that "we must bear in mind concerning this whole feat of the Athenians, that it is neither a mere myth nor unadorned history, although some take it as history and others as myth", he is treating "Crantor's view as mere personal opinion, nothing more; in fact he first quotes and then dismisses it as representing one of the two unacceptable extremes".
Cameron also points out that whether he refers to Plato or to Crantor, the statement does not support conclusions such as Otto Muck's "Crantor came to Sais and saw there in the temple of Neith the column, completely covered with hieroglyphs, on which the history of Atlantis was recorded. Scholars translated it for him, and he testified that their account fully agreed with Plato's account of Atlantis" or J. V. Luce's suggestion that Crantor sent "a special enquiry to Egypt" and that he may simply be referring to Plato's own claims.
Another passage from Proclus' commentary on the Timaeus gives a description of the geography of Atlantis:
That an island of such nature and size once existed is evident from what is said by certain authors who investigated the things around the outer sea. For according to them, there were seven islands in that sea in their time, sacred to Persephone, and also three others of enormous size, one of which was sacred to Hades, another to Ammon, and another one between them to Poseidon, the extent of which was a thousand stadia [200 km]; and the inhabitants of it—they add—preserved the remembrance from their ancestors of the immeasurably large island of Atlantis which had really existed there and which for many ages had reigned over all islands in the Atlantic sea and which itself had like-wise been sacred to Poseidon. Now these things Marcellus has written in his Aethiopica".
Marcellus remains unidentified.
Other ancient historians and philosophers believing in the existence of Atlantis were Strabo and Posidonius.