Republic is generally placed in the middle period of Plato's dialogues. However, the distinction of this group from the early dialogues is not as clear as the distinction of the late dialogues from all the others. Nonetheless, Ritter, Arnim, and Baron—with their separate methodologies—all agreed that the Republic was well distinguished, along with Parmenides, Phaedrus and Theaetetus.[8]
However, the first book of the Republic, which shares many features with earlier dialogues, is thought to have originally been written as a separate work, and then the remaining books were conjoined to it, perhaps with modifications to the original of the first book.[8]