How do speakers tease apart a simple generic sentence ( les instituteurs ne gagnent pas beaucoup d’argent “school teachers do not make much money”) and a proverb ( les cordonniers sont les plus mal chaussés, “shoemakers are always the worst shod”, eng. The cobbler’s children go barefoot )? From a formal viewpoint, these two utterance types are very close. Yet, only the latter is used in fields other than shoemaking. I account for this property, which I call ‘transposability’, by means of the following hypothesis, which also applies to proverbs and semantically transparent fixed expressions: a proverb correspond to a semantic form that consisting of a few semantic features organized as a semantic network. I adopt Sowa’s (1984) formalism and represent this network as a semic molecule (Rastier, 1989). To explain the transposability of the molecule, I use a notion from Gestaltheorie, namely the ‘strong form’. A proverb is freely transposable providing it lexicalizes a strong form, the strong form being a molecule with a high degree of internal coherence. Semantically speaking, I show that this coherence is a factor of both (a) an inherent or socially normed relational architecture and (b) an articulation without rests.