[[Wilhelm von Humboldt]] was a pioneering language scholar whose studies encompassed a broad selection of languages from different families around the world, notably including Basque, American, and Polynesian languages. He spent his last years studying the ancient Kawi language of Indonesia. In 1836, a year after his death, his theoretical views on language were published as "The Diversity of Human Language-Structure and its Influence on the intellectual and spiritual Development of Mankind" (''Über die Verschiedenheit des menschlichen Sprachbaus und seinen Einfluss auf die geistige Entwickelung des Menschengeschlechts''). For Humboldt, language was not merely an instrument for representing or communicating thought, but a "formative organ of thought" (''bildende Organ des Gedankens''): Different languages present "a diversity of world perspectives" (''Verschiedenheit der Weltansichten'').
Heymann Steinthal, a pupil of Humboldt, in the 1860s developed an interpretation of his mentor's notion of the "inner form" of a language. Intuition (''Anschauung'') underlying the forms of language arises unconsciously from a ''Volksgeist'', a Hegelian notion that served as a precursor to the anthropological sense of "culture". [[Franz Boas]], the founder of academic anthropology in the United States, was later to cite Steinthal as having demonstrated that "the form of thought is molded by the whole social environment of which language is part".
In 1875, [[William Dwight Whitney]], who studied under [[Franz Bopp]], published "The Life and Growth of Language: An Outline of Linguistic Science", in which he drew on Steinthal's treatment of Humboldt's notion of the "inner form" of a language to argue: "Every single language has thus its own peculiar framework of established distinctions, its shapes and forms of thought, into which, for the human being who learns that language as his ''mother-tongue'', is cast the content and product of his mind."