Thanks to @4Q248 for proof-reading this post and providing clarifying suggestions.
Lacan gives a formulation, "the unconscious structured like a language" (Seminar XX, p. 21), which has always felt mysterious to me. Known as the foundational text of "structuralism", Saussure's "Course on General Linguistics" has helped clarify this formulation by providing Lacan's working definition of a language.
Before I approach Saussure's definition, I want to set the boundaries of this post. I'm interested in interpreting Lacan's analogical claim that "the unconscious is structured like a language", and I want to bracket the question of "in what ways is the unconscious constituted by or through language?" Classic psychoanalysis only has access to the speech of the analysand, meaning that much interpretation within analysis goes on through the medium of language. But I do not want to attempt to define the essence of the unconscious as such; I will attempt to limit this discussion to the ways in which Saussure's definition of language functions as a metaphor or structural analogy for the unconscious.
Saussure believed that any single language has the following properties:
A language is a cloud of "signs", which are pairings between sound-images (signifiers) and concepts (signifieds). Saussure believed the primary space of language was speaking, with writing as a secondary but highly significant effect that develops from speaking. Here is Saussure's diagram of the linguistic sign (i.e. the entire oval containing the signifier and signified):
A language is individualized within each person (we each have our vocabularies), but exists within a larger "community of speakers" which informally (or formally, in some cases) determines the proper "value" of each sign.
A language must be analyzed along both "synchronic" and "diachronic" lines, each analysis to be performed separately.
"Synchronic" linguistics interprets the "state" of a language in the present, in the sense of grammar, accepted word usage, relationships between signs, etc. It is concerned with language as it exists and is used within a body of individuals right now. This is the "horizontal" axis of interpretation.1
"Diachronic" linguistics concerns the evolution of language states over time, e.g. etymology, as it evolves and morphs in a historical sense. This is the "vertical" axis of interpretation.
I will thus attempt to unwrap this metaphor, to draw parallels that shed light on Lacan's formulation of the unconscious:
The unconscious is a cloud of "signs", pairings between signifiers and signifieds2.
The unconscious is individualized within each person ("my" unconscious), but exists as a result of a larger communal unconscious (if viewed as a topology, its locus is the "big Other", the reification of a communal unconscious---contrast this with Marx). This move ties together the Freudian ideas of a "personal unconscious" with Jungian and later ideas of a "collective unconscious".
The unconscious must be interpreted along both "synchronic" and "diachronic" lines, each analysis to be performed separately.
A "synchronic" state of the unconscious refers to its existence in the present moment. A synchronic analysis must proceed by understanding the present contents of the unconscious, as they are presented to the analyst. This means listening and constructing an effective "mapping" of the grammar of the analysand's present set of affective value relations, as it flows linearly (transmitted via spoken sentences) and associatively (through "free" relationships between signs). The nature of analysis admits both of these forms simultaneously: the analysand cannot help but speak in a linear fashion, but the "free associative" nature of their discourse allows for the interpretation of linkages between related or associated ideas. The psychoanalytic idea of "transference" (interpreting how the analysand thinks and feels about the analyst and how the analyst responds and feels in relation to that) lives within this domain of synchronic analysis.
Synchronic analysis may also concern itself with the present methods used by the analysand to satisfy their drives, which are tied to their personality and which are "coping" behaviors (in a non-judgmental sense), that can be substituted for other behaviors as a result of reflection. Lacan takes this deeper throughout his lectures, analyzing the relationship of Saussure's "spoken chain" with his notion of the "master signifier", and relating Saussure's idea of the "linguistic circuit"3, which binds together two speaking subjects, to the basic drives.
A "diachronic" analysis of the unconscious concerns the development of the present state over time. Notions such as "trauma" concern themselves with diachronic events whose effects provide material for a historical, quasi-causal interpretation of the analysand's present state. The diachronic mode also permits analysis of the internalization process, through which the "collective unconscious" is "deposited" within, i.e. individualized by the speaker, who learns to navigate this "cloud" of ideas in order to satisfy their needs.4
Despite its usefulness, this metaphor shows some seams, as I mentioned earlier, where the metaphrand and the metaphier, unconscious and language itself, butt up against each other, tarnishing the purity of the analogy. This appears to be what Lacan addresses in Seminar XX (p. 15), starting with his idea of "linguistricks" (linguisterie, as opposed to linguistique or "linguistics") and moving forward from there. I plan to reread the seminar given this new backbone, and may write a follow-up post that dives deeper!
Saussure distinguishes further two classes of synchronic relations, the "syntagmatic relation", i.e. the successive relationship in the spoken chain, and the "associative relation", the space of "similar" terms that each given term calls to mind. The following image is used to explain the latter relation: ↩
In language, signifiers are sound-images and signifieds are concepts. But the nature of the unconscious renders this direct comparison problematic: we need to ask, what in the unconscious is analagous to the sound-image and to the concept? Arguably, any conscious image will work as an unconscious signifier, and concepts can refer to any memory or affective charge. This is subject to debate among the different schools of psychoanalysis; the exact substance of the unconscious remains somewhat elusive. But so long as we assume that the unconscious consists of a set of relationships between some sort of image and some sort of effect, the metaphor remains consistent. ↩
The following is Saussure's diagram of the spoken chain: ↩
And the following is Saussure's diagram of the linguistic circuit:
Similar to the set of synchronic relations, Saussure breaks down three forms of diachronic shift (ways that terms change over time): agglutination, analogy, and phonetic change. Whether the metaphor holds in terms of the exact mechanism of unconscious shifts is something I haven't determined. ↩