A lot depends on your opinion about Plato's Letters. Many argue they are not authentic, but then these are the same people that want to argue Plato IS giving us his philosophy. I am in the camp that understands them as authentic, in large part because having read all of Plato's works, with a background in reading attic Greek, shows me that there are a LOT of contradictions within what Plato writes if one attempts to suggest there is a consistent philosophy therein.
Good stuff!