A reason for not revealing it to everyone is partially discussed in "Phaedrus" where Plato criticizes the written transmission of knowledge as faulty, favouring instead the spoken logos: "he who has knowledge of the just and the good and beautiful ... will not, when in earnest, write them in ink, sowing them through a pen with words, which cannot defend themselves by argument and cannot teach the truth effectually." The same argument is repeated in Plato's "Seventh Letter": "every serious man in dealing with really serious subjects carefully avoids writing." In the same letter he writes: "I can certainly declare concerning all these writers who claim to know the subjects that I seriously study ... there does not exist, nor will there ever exist, any treatise of mine dealing therewith." Such secrecy is necessary in order not "to expose them to unseemly and degrading treatment".