The key formative figure in the intellectual life of the young Ferdinand de Saussure was Adolphe Pictet (1799–1875), a family friend best remembered for his Les origines indo-européennes, ou Les Aryas primitifs: Essai de paléontologie linguistique (1859–1863). A review of its second edition written by Saussure two years after Pictet’s death contains a wealth of information about his life and work, including a description of his book Du beau, dans la nature, l’art et la poésie: Etudes esthétiques (1856). In it, Pictet makes clear that aesthetics is principally centred on the problem of the meaning of the word beauty, and that within this problem are to be found all the tensions between the rational and sensible, the intellectual and emotional, the subjective and objective, and intention and reaction, that are at the heart of the whole Enlightenment discourse on the nature of language. A number of remarks on regularity of form in nature, for example in crystallisation, find echoes in Saussure’s later characterisation of the language system, as do Pictet’s assertions about the arbitrary nature of the linguistic sign and about the signified being not a thing but a concept. Indeed, a number of ‘influences’ on Saussure which Aarsleff (1982) credited to Hippolyte Taine (1828–1893) – for whom we have no independent evidence of such influence – can more convincingly be ascribed to his early mentor Pictet. Du beau moreover provides a ‘missing link’ between the Enlightenment philosophers whose aesthetic views it details, and the traces of their philosophical positions that have repeatedly been detected in the Cours de linguistique générale.