Between Plato and the Pre-Socratics, there was an original discord between philosophy and anti-philosophy. The Pre-Socratics accepted the ‘primacy of discourse’, whereas Plato affirmed some “real” thing beneath discourse. That is why we can call Plato’s philosophy idealistic, since he believes in something ideally real, (the Platonic real), whereas the only real things our language talks about is the difference within itself, according to the Pre-Socratics.
But Plato’s philosophy was simultaneously innocent and grandiose. Grandiose because he thought that language was commensurable with the Real. Innocent because his philosophic fiction has been superseded by every philosophic movement after Descartes. It was superseded by the mind-turn of the Enlightenment, where the origin of signifiers were relocated in the mind rather than the world, and the linguistic turn of the 20th Century where the origin of signifiers were relocated in language rather than in the mind.
It appears that the Pre-Socratics had it right. Their views were seen as anti-philosophic early on, since they opposed the formulaic reduction of language to the Real which later became the duty of the philosopher. I should say that there is really only one Pre-Socratic I have in mind here, to be fair to all the rest, and that is Heraclitus. He is known as the Philosopher of Discord. Whereas Plato and Socrates preached harmony, according to the Heraclitus’ aphorisms, Discord and non-relation is more fundamental than harmony.