In “Plato’s Pharmacy,” Derrida deconstructs the dual meaning of the word “supplement:” as a substitute and as an addition. He invokes the notion of the supplement throughout this critique of various binaries that Western metaphysical philosophy has left unquestioned, all of which value presence over absence. This hierarchy is erroneous, Derrida argues, because the desire for full presence is the result of its impossibility; the concept of presence cannot exist without that of absence. Freud similarly acknowledges in his analyses that the workings of the unconscious are not, and never will be, available to the conscious mind of the patient or the analyst. This rejection of the search for complete epistemic presence is common to deconstruction and Freudian psychoanalysis.
In the preface to Three Essays on the Theory of Sexuality, Freud describes his psychoanalytic method as “distant . . . from the reality which it is its business to discover” (xxix). In other words, a thought, dream, or memory’s unconscious signification is already lost once a patient begins to consciously think or relate it. All possibilities of original presence of meaning, like “the absolute present” or “Nature” in Derrida, “have always already escaped, have never existed” (Of Grammatology 159). This constant escape is the result, according to Freud’s The Interpretation of Dreams, of two psychological processes: condensation and displacement.
Condensation is the construction of a metaphor from unconscious symbols, in which a sign, such as a word (thought or spoken) or a dream symbol, stands in for another. However, this is not a one-to-one, cause and effect relationship; many unconscious factors can be manifested in a single representation, and one unconscious thought can influence many conscious signifiers. The former case is most common — that condensation compresses several unconscious signifiers into one conscious one. In a dream, for instance, one symbol is often the additive result of many “dream-thoughts.” Signifiers are connected in complex ways in both directions, and this chain of associations goes on indefinitely, so that “even if the solution seems satisfactory and without gaps, the possibility always remains that the dream may have yet another meaning. Strictly speaking, then, it is impossible to determine the amount of condensation” (Interpretation of Dreams 313).
In displacement, a sort of mental metonymy, one signifier draws attention away from itself by slipping under another. The result is that a dream’s content becomes different from the thoughts that espoused it. For instance, a statement one hears in a dream is sometimes “no more than an allusion to an occasion on which the remark in question was made” (339). This happens when the original occasion is repressed; its displacement both conceals it and provides a means by which to reveal it to the conscious mind.
In the process that Freud calls “overdetermination,” thoughts containing “psychical intensities” too disturbing to conceive of are displaced onto “elements of low psychical value.” Overdetermination plays a pivotal role in the alienation — similar to Derrida’s difference — of the subject from his own dream-thoughts. Paradoxically, it is the presence of a signifier in consciousness that distances one from complete knowledge of what it signifies. It is through such displacement that “the difference between the text of the dream-content and that of the dream-thoughts comes about” (343).
Derrida too uses the word “overdetermination” to describe the compression of multiple meanings into one signifier within a text. In his example of “pharmakon,” overdetermination has “permitted the rendering of the same word by ‘remedy,’ ‘recipe,’ ‘poison,’ ‘drug,’ ‘philter,’ etc.” In its deconstruction of the writing/speech binary, “Plato’s Pharmacy” uses this presence of multiple meanings within a signifier, which escape a speaker’s conscious awareness, as an example of how the fullness of self supposedly lost in writing is actually absent in speech. It is impossible to infer some natural, pre-linguistic origin or whole significance from somebody’s spoken accounts because a concept’s “rules and the strange logic that links it with its signifier, has been dispersed, masked, obliterated” (71-72).
The bits of information Freud’s patients disclosed could be characterized as supplements to the experiences, wishes, fantasies, and emotions that have produced them, that they have always already displaced. In The Interpretation of Dreams, condensation and displacement play the role of censoring dream-thoughts in a way analogous to, respectively, the substitutive and additive effects of the supplement. A conscious association serves this dual function of an addition, in the sense that it still drags along all the unconscious thoughts it has latched onto, and of a substitute, in the sense that these thoughts cannot be fully understood; the language of the unconscious is always already hidden behind the conscious addition/replacement. “Superficial associations· are only substitutes by displacement for suppressed deeper ones,” Freud cites as a tenet of psychoanalysis. “When I instruct a patient to abandon reflection of any kind and to tell me whatever comes into his head, I am relying firmly on the presumption that he will not be able to abandon it” (570).
Freudian psychoanalysis is in accordance with Derrida’s assertion that there is nothing understood outside language, and both reflect the Heideggerian philosophy that language speaks humans before they speak. According to Louis Althusser’s reading of Freud, psychoanalysis is done “in and through language.” The unconscious is not natural and fixed, but culturally constructed from the start. Thus, “slips, failures, jokes and symptoms, like the elements of dreams themselves, become signifiers” — which themselves contain signifiers (“Freud and Lacan” 207).
This view of thought as a collection of linguistic associations disrupts the notion of the self as a stable, unified, whole entity. Thus, somebody’s utterances can mean something that the subject himself doesn’t intend to say. Though writing has been seen as a supplement to speech that prohibits the full presence of self, speech itself involves absence of the subject. Derrida shows in his reading of Rousseau — who utters things contrary to what he intends — how speech can reveal someone’s discordance with himself (Johnson xiii).
Derrida’s goal in reading a text — and all language is a text — is not to decipher the author’s identity or intentions, which are already absent, but rather to look at how signification, myth, and ideology are operating. As applied to psychoanalysis, the difference between rhetoric and intention implies there is no singular, original source from which speech or thought emanates. Dreams are not decoded, but read. The conscious intention is not the true meaning, but the supplement to a meaning that is already absent through condensation or displacement. Psychoanalysis and deconstruction each demonstrate that the “truth” of a discourse, or “as we shall see, (the) nontruth, cannot by observed in ourselves or by ourselves” (Plato’s Pharmacy” 74).