Barthes describes the advance as:

an almost unique specification of the face, which has nothing of essence left in it, but is constituted by an infinite complexity of morphological functions. As a language, Garbo's singularity was of the order of the concept, that of Audrey Hepburn is of the order of the substance. The face of Garbo is an Idea, that of Hepburn, an Event. (Mythologies, 57)