The chain, pharmakeia-pharmakon-pharmakeus, appears several times in Plato's texts. A word not directly or literally used by Plato is pharmakos, which means 'scapegoat'. According to Derrida, that it is not used by Plato does not indicate that the word is necessarily absent. Certain forces of association unite the words that are 'actually present' in a text with all the other words in the lexical system, whether or not they appear as words in such discourse. The textual chain is not simply 'internal' to Plato's lexicon. One can say that all the 'pharmaceutical' words do actually make themselves present in the text. 'It is in the back room, in the shadows of the pharmacy, prior to the oppositions between conscious and unconscious, freedom and constraint, voluntary and involuntary, speech and language, that these textual 'operations' occur' (Dissemination, p.129). Derrida places the opposites, presence-absence and inside-outside, under great pressure. If the word pharmakos that Plato does not use still resonates within the text, then there can be no matter of a text being closed upon itself. What do 'absent' and 'present' mean when the outside is always already part of the inside, at work on the inside?
 In ancient Athens, the character and the ritual of the pharmakos had the task of expelling and shutting out the evil (out of the body and out of the city). The Athenians maintained several outcasts at the public expense. When plague, famine, drought or other calamities befell the city, they sacrificed some of the outcasts as a purification and a remedy. The pharmakos, the scapegoat, was led to the outside of the city and killed in order to purify the city's interior. The evil that had affected the inside of the city from the outside, was thus returned to the outside in order to protect the inside. But the representative of the outside (the pharmakos) was nonetheless kept in the very heart of the inside, the city. In order to be led out of the city, the scapegoat must have already been within the city. 'The ceremony of the pharmakos is thus played out on the boundary line between the inside and the outside, which it has as its function ceaselessly to trace and retrace' (Dissemination, p.133). At the same time, the pharmakos is on the borderl between sacred and cursed, '... beneficial insofar as he cures - and for that, venerated and cared for - harmful insofar as he incarnates the powers of evil - and for that, feared and treated with caution' (Dissemination, p.133). He is the benefactor who heals and he is the criminal who incarnates the powers of evil. The pharmakos is like a medicine in that he 'cures' the impurity of the city, but he is, at the same time, a poison, an evil. Pharmakos. Pharmakon. Undecidables. Both words carry within themselves more than one meaning. Conflicting meanings.
 Pharmakos does not only mean scapegoat. It is also synonymous for pharmakeus, or wizard, magician, poisoner. In Plato's dialogues, Socrates is often portrayed as a pharmakeus. Socrates is considered as one who knows how to perform magic with words. His words act as a pharmakon (as a remedy, or as a poison?) and permeate the soul of the listener. In Phaedrus, he fiercely objects to the ill effects of writing. He compares writing to a pharmakon, a drug, a poison: writing repeats without knowing. Socrates suggests a different pharmakon, a medicine: dialectics, the philosophical dialogue. This, he claims, can lead one to true knowledge, the truth of the eidos, that which is identical to itself, always the same as itself, invariable. This is the message of Socrates to the city of Athens. He acts as a magician (pharmakos) - Socrates himself speaks about a divine or supernatural voice that comes to him - and his most famous medicine (pharmakon) is speech, dialectics and dialogue that will lead to knowledge and truth.
But Socrates also becomes Athen's most famous 'other' pharmakos, the scapegoat. He becomes a stranger, even an enemy who does not speak the proper language of the other citizens. He is an other; not the absolute other, the barbarian, but the other (the outside) who is very near, who is already on the inside. According to several prominent Athenians, he was of bad moral and political influence. His constant criticism undermined the faith in democracy of many Athenians. In 399 BC, Socrates was charged with introducing new gods and corrupting the young and sentenced to death. Having accused him as a force of evil, Athens killed him to keep itself intact. Athens kills the pharmakos (both the magician and the scapegoat).