The document discusses Leonard Bloomfield, a prominent 20th century American linguist who established structural linguistics. It describes how Bloomfield initially developed his linguistic theory within Wilhelm Wundt's conceptualist psychology framework but later adopted behaviorism. Bloomfield analyzed language structure into hierarchical levels of phonemes, morphemes, words, phrases and sentences. He developed theories of phonology, morphology and syntax but less for semantics. Ultimately, structural linguistics declined because behaviorism could not adequately explain semantic theory for natural languages.