Plato and his Predecessors

How does Plato view his philosophical antecedents? Plato and his Predecessors considers how Plato represents his philosophical predecessors in a late quartet of dialogues: the Theaetetus, the Sophist, the Politicus and the Philebus. Why is it that the sophist Protagoras, or the monist Parmenides, or the advocate of flux, Heraclitus, are so important in these dialogues? And why are they represented...