Of course there has been much debate on Plato's philosophy, and whether (and to what extent) he had an esoteric philosophy reserved only to his students in the Academy, and the dialogues are only popular presentations of some of his theses.

At least Aristotle seems to think about Plato a bit in this way (in Metaphysics, for example; in Poetics he mentions the dialogues are one sort of literature, I think).

Kant did want to construct a system, but I think it would be a bit unfair to say what Schopenhauer wanted to build was a system in a strict sense. What I mean is that Schopenhauer thought (philosophical) concepts or language would lead us astray - only intuition can reach what is real.

I would say his "system" is more about spreading the thought (of intuition, etc.): it's like in most religions, the "book" is not what there is to it. A bad comparison, I know.

Nietzsche was strictly against all kinds of system building, even the one he found in Schopenhauer. Nietzsche was sharp and diagnostic...

Returning to Plato, it's always a big question, having to do most of all with Plato's epistemology and ontology (this and the other topic), whether he really had those.

What do you think?