Once again, however, things in Syracuse were not at all to Plato's liking.
Dionysius once again effectively imprisoned Plato in Syracuse, and the latter was only able to escape again with help from his Tarentine friends ( 350a-b).
Plato, perhaps now completely disgusted with politics, returned to his beloved Academy, where he lived out the last thirteen years of his life. His grave, however, has not yet been discovered by archeological investigations. There can be no doubt that Plato was also strongly influenced by Parmenides and Zeno (both of Elea), in Plato's theory of the Forms, which are plainly intended to satisfy the Parmenidean requirement of metaphysical unity and stability in knowable reality.
According to Diogenes, Plato was buried at the school he founded (D. Aristotle and Diogenes agree that Plato had some early association with either the philosophy of Heraclitus of Ephesus, or with one or more of that philosopher's followers (see Aristotle Metaph. Parmenides and Zeno also appear as characters in his dialogue, the He mixed together in his works the arguments of Heracleitus, the Pythagoreans, and Socrates. 3.8) A little later, Diogenes makes a series of comparisons intended to show how much Plato owed to the comic poet, Epicharmus (3.9-3.17).
These works blend ethics, political philosophy, moral psychology, epistemology, and metaphysics into an interconnected and systematic philosophy.