In the extensive literature on Plato's “unwritten doctrine” there is still no treatise on the question: Why did Plato not write the “unwritten doctrine”? The present study presents this and can also be read as an introduction to Plato's unwritten philosophy. Drawing on analyses of the decisive passages from the Platonic dialogues, as well as the Seventh Letter, it argues that Plato did not publish the “unwritten doctrine” in writing not only because of the inadequate reception conditions of unprepared readers, but also because he did not claim to have a definitive knowledge of the principles and also therefore could not fix them in writing for the public once and for all.
