Final answer:
Socrates is going to the Piraeus to attend a festival at the start of Plato's 'The Republic,' which begins a deep dialogue on the nature of justice.
Step-by-step explanation:
When Plato's The Republic opens, Socrates is heading to the Piraeus to attend a festival in honor of the goddess Bendis. The opening of The Republic sets the stage for a profound dialogue on the nature of justice, initiated by Socrates' questioning whether justice is simply an instrument of power or intrinsically valuable. Plato utilizes the character of Socrates to explore these philosophical questions, primarily through Socratic method, a form of cooperative argumentative dialogue that stimulates critical thinking and illuminates ideas.