At first acoustics attributed to the different sounds only a limited number of characteristic features.
In poetic language, in which the sign as such takes on an autonomous value, this sound symbolism becomes an actual factor and creates a sort of accompaniment to the signified.
Acoustic phonetics, which is developing and increasing in richness very rapidly, already enables us to solve many of the mysteries of sound, mysteries which motor phonetics could not even begin to solve.
Semantics, or the study of meaning, remained undeveloped, while phonetics made rapid progress and even came to occupy the central place in the scientific study of language.
It is once again the vexing problem of identity within variety; without a solution to this disturbing problem there can be no system, no classification.
Every linguistic sign is located on two axes: the axis of simultaneity and that of succession.