Critias is the title of one of the two dialogues of Plato that gave the world its first unambiguous mention of Atlantis. Benjamin Jowett’s English translation of 1871 is widely available on the Internet(a) as it is now out of copyright.
The Critias dialogue ends in the middle of a sentence while on the point of revealing more about Atlantis. This fact has generated regular comment over the centuries and some have concluded that Plato grew tired of the Atlantis story, while others suggest that he was at the end of his writing career and old age or illness prevented him from finishing the dialogue. However, since it is accepted that Plato’s Laws, which also ends abruptly,was written later than Critias the idea that death prevented its completion does not hold up.
*Perhaps relevant to the incomplete Critias, is the suggestion that there is an entire intended dialogue missing, apparently with the possible title of Hermocrates. This would appear to be confirmed by Critias 108 which twice mentions, in the same passage, that Hermocrates is due to make a contribution of some substance, which the repetition implies!*
H. S. Bellamy in his book The Atlantis Myth points out that there is no evidence of any classical writer commenting on the unfinished nature of Critias until Plutarch, at the beginning of the second century AD. The implication of this is that the original manuscript was completed but somehow over the centuries the final part of Critiaswas lost. It is easier to believe that the final incomplete sentence was originally at the end of a line of text at the bottom of a page that became separated from the following leaves than imagine that a person of Plato’s literary stature was incapable of finishing a sentence. I am tempted to subscribe to this theory and hope that somehow a copy of the ‘missing’ pages turn up in some obscure library.
George Sarantitis offers a novel explanation for the sudden ending of Critias. He proposes that Plato finished his narrative where Zeus was about to speak in the expectation that his audience would have been guided by the earlier content of Timaeus to complete the text with an utterance by Zeus in Homer’s Odyssey (1.32-34) “O alas, the manner in which the mortals put the blame on the gods. For they claim that from us do derive their misfortunes, yet often they themselves with their wicked deeds (hubristically behaviour) fall into grief beyond what can be written.” (Sarantitis’ translation).
His full argument can be read online(c).
A few years ago a Greek by the name of Keramidas produced what he claimed was the missing ending to Critias(b). It was an unconvincing piece that was quickly dismissed as spurious.
(c) http://platoproject.gr/mom-1/ (section 5)