After the dialogue between Socrates and Phaedrus has essentially come to a conclusion in Phaedrus, Plato has Socrates relate the myth about Theuth. This myth thus appears as a kind of encore, an epilogue, an hors-d'oeuvre (literally: outside the work), a supplement. But what starts as a supplement, is found to be the most essential part of Phaedrus. It is an accusation against writing since writing would replace living memory for a mnemonic device. Plato presents writing as the sign of a sign. Speech remains in animate proximity, in the living presence of mneme. Writing, which imitates and reproduces living speech, goes one degree further. 'The boundary (between inside and outside, living and non-living) separates not only speech from writing but also memory as an unveiling (re-)producing a presence from re-memoration as the mere repetition of a monument' (Dissemination, p.108-9). The difference between mneme and hypomnesis. The problem starts where the mneme, instead of being present to itself, is supplanted by archives, lists, notes, tales, accounts, chronicles: memorials instead of memory. But, as Derrida indicates, the 'evil' slips in within the relation of memory to itself, in the general organization of the mnesic activity. Memory always needs signs in order to recall the non-present, with which it is necessarily in relation. The line between mneme and hypomnesis becomes barely perceptible because in both cases it is a matter of repetition. Memory is always already contaminated by its first substitute: hypomnesis. The outside (the replacing sign) is already within the work of memory. What Plato dreams of is the possibility of a memory with no sign; that is, with no supplement (cf. Dissemination, p.109).
 In the myth, the god Theuth offers writing as a pharmakon to King Thamus of Egypt. It is a recipe for both memory and wisdom. Who is this Theuth, Plato's god of writing? Derrida shows that Plato's Theuth has much in common with two other gods of writing, the Egyptian god, Thoth and the Greek god, Hermes. In Egyptian mythology, Thoth often calls himself the son of the sun-god, Ammon-Ra. Ammon: 'the hidden'. The hidden sun, the father of all. He allows himself to be represented by Thoth. Thoth speaks in the name of Ammon-Ra. Thoth is the language through which Ammon-Ra enters the human world. In Derridian terms, this means that the father needs language in order to appear. Like his Greek counterpart, Hermes, Thoth is the messenger-god, an intermediary. But he can only convey what has already been thought by Ammon. Language is thus considered to be a representation of a more original thought. 'The message itself is not, but only represents, the absolutely creative moment. It is a second and secondary word' (Dissemination, p.88). Thoth, Hermes, and Theuth: the gods of writing are subordinate characters. They are but servants and executors. Never the authors or initiators of language.