Ferdinand de Saussure
The sign is constituted by two elements:
- the signified, a conceptual element (or concept), and
- the signifier, a phonological element (or sound-image).
The two elements are linked by an arbitrary but unbreakable bond.
Saussure represented the sign by means of a diagram.<ref>Saussure, Ferdinand de. (1916) Course in General Linguistics, ed. Charles Bally and Albert Sechehaye, trans. Wade Baskin, Glasgow: Collins Fontana. p.114</ref> In this diagram, the line between the signified and the signifier represents union, the reciprocal implication of the two elements. (Saussure put the signifier and the signified in an ellipse which indicates structural unity of the sign.)
Lacan takes up the Saussurean concept of the sign in his "linguistic turn" in psychoanalysis during the 1950s, but subjects it to several modifications. During the 1950s Lacan began to make us of Saussure's concepts but adapted them in important ways.
Relation between Signifier and Signified
Firstly, whereas Saussure posited the reciprocal implication between signifier and signified (they are as mutually interdependent as two sides of a sheet of paper), Lacan argues that the relation between signifier and signified is extremely unstable.
Primacy of the Signifier
Secondly, Lacan asserts the existence of an order of "pure signifiers," where signifiers exist prior to signifieds; this order of purely logical structure is the unconscious. This amounts to a destruction of Saussure's concept of the sign; for Lacan, a language is not composed of signs but of signifiers.
Saussurean algorithmSaussure, Lacan replaces Saussure's diagram of the sign with an algorithm which, Lacan argues, should be attributed to Saussure -- and is thus now sometimes referred to as the "Saussurean algorithm."<ref>Lacan, Jacques. Écrits: A Selection. Trans. Alan Sheridan. London: Tavistock Publications, 1977. p.149</ref> The S stands for the signifier, and the s for the signified; the position of the signified and the signifier is thus inverted, showing the primacy of the signifier (which is capitalized, whereas the signifier is reduced to mere lower-case italic). The arrows and the circle are abolished, representing the absence of a stable or fixed relation between signifier and signified. The bar between the signifier and the signified no longer represents union but the resistance inherent in signification. For Lacan, this algorithm defines "the topography of the unconscious."<ref>Lacan, Jacques. Écrits: A Selection. Trans. Alan Sheridan. London: Tavistock Publications, 1977. p. 163</ref>