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.
