Language can be compared to a sheet of paper: thought is its recto and sound its verso: one cannot cut the verso without simultaneously cutting the recto. Similarly, in the matter of language, one can separate neither sound from thought nor thought from sound; such separation could be achieved only by abstraction, which would lead either to pure psychology, or to pure phonology.

p. 157; as cited in: Schaff (1962:11) - Cours de linguistique générale (1916)