The Republic is linked to the Timaeus by the latter's preface, and also by the appearance in the Timaeus of the Atlantis story, which continues in the unfinished Critias. There are problems, well-known to scholars, with the link provided in the preface by the references to the Republic. Socrates in the Timaeus summarizes a speech he gave “yesterday” – but he is at a different festival, in entirely different company. He refers back to the ideal state in the Republic, but in a strikingly selective way. He touches on the communal life of the Guardians in Book 5 of the Republic, but he elides the Republic's distinction between the Guardians and the Auxiliaries, and, most strikingly, makes no mention at all of the point that the rulers of the ideal state are to be philosophers.

Some scholars have taken these divergences to indicate that we are not meant to think here of the whole Republic as we have it, but this does not solve any problems, since, as we shall see, the link between the dialogues provided by the Atlantis story requires us to bear in mind the Republic's main argument about virtue as well as the part about the ideal state. I have no solution to the anomalies in the preface beyond the rather obvious suggestion that Plato wants to link the argument of the Republic with the cosmological project of the Timaeus, and does so by means of selective reference to the Republic in a new context, one in which he refers only to the ideal state in Book 5.