Which of the following theorists identifies “metonymy” and “metaphor” as two fundamental structures of language?

The correct option is Roman Jacobson.

Roman Jakobson (spelled Roman Jacobson in the options) was a pioneering Russian-American linguist and literary theorist who made significant contributions to structural linguistics.
In his seminal 1956 essay, "Two Aspects of Language and Two Types of Aphasic Disturbances", Jakobson argued that language processing operates along two fundamental axes: selection and combination.

He mapped these two axes to two primary rhetorical modes, describing them as the twin poles of language:
1. The Metaphoric Pole (Similarity / Selection): This represents the axis of selection, where a speaker chooses a specific word from a paradigm of similar or substitutable words. Metaphor operates on this principle of similarity, replacing one term with another based on their shared characteristics.
2. The Metonymic Pole (Contiguity / Combination): This represents the axis of combination, where words are linked together sequentially to form a sentence. Metonymy operates on this principle of contiguity, where things are linked based on association, context, spatial proximity, or cause-and-effect.

By analyzing patients with aphasia (a speech disorder), Jakobson demonstrated that speakers who suffer from a breakdown in the selection process struggle with metaphor, while those who suffer from a breakdown in the combination process struggle with metonymy. This clinical evidence supported his theory that metaphor and metonymy are indeed the two fundamental structures underlying all human language. In contrast, Ferdinand de Saussure focused on the signifier/signified, Roland Barthes applied semiotics to culture and myth, and J.L. Austin developed the theory of speech acts.