The only primary sources for Atlantis are Plato's dialogues Timaeus and Critias; all other mentions of the island are based on them. The dialogues claim to quote Solon, who visited Egypt between 590 and 580 BC; they state that he translated Egyptian records of Atlantis. Plato introduced Atlantis in Timaeus, written in 360 BC:
The four people appearing in those two dialogues are the politicians Critias and Hermocrates as well as the philosophers Socrates and Timaeus of Locri, although only Critias speaks of Atlantis. In his works Plato makes extensive use of the Socratic method in order to discuss contrary positions within the context of a supposition.
The Timaeus begins with an introduction, followed by an account of the creations and structure of the universe and ancient civilizations. In the introduction, Socrates muses about the perfect society, described in Plato's Republic (c. 380 BC), and wonders if he and his guests might recollect a story which exemplifies such a society. Critias mentions a tale he considered to be historical, that would make the perfect example, and he then follows by describing Atlantis as is recorded in the Critias. In his account, ancient Athens seems to represent the "perfect society" and Atlantis its opponent, representing the very antithesis of the "perfect" traits described in the Republic.
According to Critias, the Hellenic deities of old divided the land so that each deity might have their own lot; Poseidon was appropriately, and to his liking, bequeathed the island of Atlantis. The island was larger than Ancient Libya and Asia Minor combined, but it was later sunk by an earthquake and became an impassable mud shoal, inhibiting travel to any part of the ocean. Plato asserted that the Egyptians described Atlantis as an island consisting mostly of mountains in the northern portions and along the shore and encompassing a great plain in an oblong shape in the south "extending in one direction three thousand stadia [about 555 km; 345 mi], but across the center inland it was two thousand stadia [about 370 km; 230 mi]." Fifty stadia [9 km; 6 mi] from the coast was a mountain that was low on all sides ... broke it off all round about ... the central island itself was five stades in diameter [about 0.92 km; 0.57 mi].
In Plato's metaphorical tale, 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 toward 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 ring of the city. 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.
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 had 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.
The logographer Hellanicus of Lesbos wrote an earlier work entitled 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 Plato writes about the genealogy of Atlantis's kings, he writes in the same style as Hellanicus, suggesting a similarity between a fragment of Hellanicus's work and an account in the Critias. Rodney Castleden suggests that Plato may have borrowed his title from Hellanicus, who may have based his work on an earlier work about Atlantis.
Castleden has pointed out that Plato wrote of Atlantis in 359 BC, when he returned to Athens from Sicily. He notes a number of parallels between the physical organisation and fortifications of Syracuse and Plato's description of Atlantis. Gunnar Rudberg was the first who elaborated upon the idea that Plato's attempt to realize his political ideas in the city of Syracuse could have heavily inspired the Atlantis account.[29]
Some ancient writers viewed Atlantis as fictional or metaphorical myth; others believed it to be real. Aristotle believed that Plato, his teacher, had invented the island to teach philosophy. The philosopher Crantor, a student of Plato's student Xenocrates, is cited often as an example of a writer who thought the story to be historical fact. His work, a commentary on Timaeus, is lost, but Proclus, a Neoplatonist of the fifth century AD, reports on it. The passage in question has been represented in the modern literature either as claiming that Crantor 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:
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; whether this referred to Crantor or to Plato is the subject of considerable debate. Proponents of both Atlantis as a metaphorical myth and Atlantis as history have argued that the pronoun refers to Crantor.
Alan Cameron argues that the pronoun 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"[35] 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.[34]
Another passage from the commentary by Proclus on the Timaeus gives a description of the geography of Atlantis:
Marcellus remains unidentified.
Other ancient historians and philosophers who believed in the existence of Atlantis were Strabo and Posidonius. Some have theorized that, before the sixth century BC, the "Pillars of Hercules" may have applied to mountains on either side of the Gulf of Laconia, and also may have been part of the pillar cult of the Aegean. The mountains stood at either side of the southernmost gulf in Greece, the largest in the Peloponnese, and it opens onto the Mediterranean Sea. This would have placed Atlantis in the Mediterranean, lending credence to many details in Plato's discussion.
The fourth-century historian Ammianus Marcellinus, relying on a lost work by Timagenes, a historian writing in the first century BC, writes that the Druids of Gaul said that part of the inhabitants of Gaul had migrated there from distant islands. Some have understood Ammianus's testimony as a claim that at the time of Atlantis's sinking into the sea, its inhabitants fled to western Europe; but Ammianus, in fact, says that "the Drasidae (Druids) recall that a part of the population is indigenous but others also migrated in from islands and lands beyond the Rhine" (Res Gestae 15.9), an indication that the immigrants came to Gaul from the north (Britain, the Netherlands, or Germany), not from a theorized location in the Atlantic Ocean to the south-west. Instead, the Celts who dwelled along the ocean were reported to venerate twin gods, (Dioscori), who appeared to them coming from that ocean.
During the early first century, the Hellenistic Jewish philosopher Philo wrote about the destruction of Atlantis in his On the Eternity of the World, xxvi. 141, in a longer passage allegedly citing Aristotle's successor Theophrastus