The quarrel that defined philosophy
The platform reads Plato's lifelong quarrel with the sophists as the conflict that, more than any other, defined what philosophy is. The sophists were the professional intellectuals of fifth-century Athens — travelling teachers who, for high fees, taught the art of persuasion, of winning arguments and swaying assemblies, the skills an ambitious man needed to succeed in a democracy. Plato opposed them root and branch, and the platform reads the opposition as turning on the deepest question of all: whether there is a truth about how to live and what is just, or only the stronger argument and the more persuasive speech.
Truth against persuasion
The platform reads the surface of the quarrel as the conflict between philosophy and rhetoric. The sophist, in Plato's portrait, aims to persuade regardless of truth — to make the weaker argument appear the stronger, to produce conviction without knowledge; the philosopher aims at the truth itself, however unwelcome. The Gorgias stages this directly: rhetoric is a "knack" of flattery, giving the audience what pleases rather than what is good, the pastry-cook against the doctor. The platform reads Plato's charge as the permanent objection to persuasion divorced from knowledge — the danger that in public life the more eloquent speaker, not the wiser one, will prevail.
Convention against nature
The platform reads the deeper level of the quarrel as the dispute over whether morality is real or merely conventional. The most radical sophists held that justice is a human convention — that "by nature" the strong rule and take what they can, and that conventional morality is a device by which the weak restrain the strong, to be discarded by anyone strong and clever enough. This is the position of Thrasymachus in the Republic ("justice is the interest of the stronger") and of Callicles in the Gorgias. The platform reads the whole of Plato's ethics — the insistence that justice is real, a knowledge and a good for the soul — as the answer to this sophistic realism: the most sustained defence ever written of the claim that morality is grounded in something more than power.
Why the platform reads it
The platform reads Plato versus the sophists as the founding conflict of moral philosophy, and one whose terms have never changed. Every age has its sophists — those who teach that justice is a name for the interest of the strong, that persuasion is everything and truth a fiction — and every age must answer them as Plato did, or concede the point. The platform reads the quarrel as live, and as the reason Plato remains the indispensable defender of the idea that there is a truth about the good worth pursuing, the deeper subject of Socrates and the Sophists.