What does it show?
The torus is one of the surfaces Lacan turned to most often. In the seminar L’identification (1961–1962) Lacan suggested that demand is a movement that goes round the tube, repeated and returning each time to the same point, while desire is the tour that these repetitions as a whole trace, unnoticed, round the central hole. The counter in the model shows this: however many demands there are, the tour of desire is counted only once, when all of them are complete.
The hole of the torus is the place not of desire’s object but of its lack; none of the demands fills this void, but all of them go round it. The object Lacan later called the objet a is what holds the place of this void.
In the “Subject and Other” mode two tori pass through each other. The two highlighted circles are two faces of the same movement: a demand that goes round the tube on the subject’s torus is, on the Other’s torus, a tour round the hole, that is, its desire. With this figure Lacan showed that the subject’s demand corresponds to the Other’s desire and the subject’s desire to the Other’s demand; this is the structure of the neurotic subject’s taking the Other’s demand for his own desire.
Related essay: Objet petit a