Wilhelm von Humboldt (1767–1835) was a Prussian diplomat and educational reformer, founder of the University of Berlin (today the Humboldt University), and the elder brother of the naturalist Alexander von Humboldt. In his last years, out of public office, he immersed himself in Kawi, an old literary language of Java, and wrote an introduction to his three-volume study of it. The introduction grew into a book of its own, published the year after his death by his brother: On the Diversity of Human Language Construction and Its Influence on the Mental Development of the Human Species (1836).

It is not a systematic textbook. Each section shifts theme; long sentences pile clause on clause; the tone is aphoristic. And yet almost every question later linguistics would pose is already here — eighty years before Saussure’s Course (1916), eighty-five before Sapir’s Language (1921).

1. Language is not a “product (ergon)” but an “activity (energeia)”

ergon = product dictionary, grammar, paradigm tables = a dead deposit (todter Niederschlag) how a scholar treats language as a "thing that is there" energeia = activity the act of speaking itself produced anew each time "its true definition can therefore only be a genetic one"
Humboldt's founding thesis. The reality of a language is not its dictionary or grammar but the ceaseless carrying-out of the act of speaking. Diagram: L/LAB

Die Sprache, in ihrem wirklichen Wesen aufgefasst, ist etwas beständig und in jedem Augenblicke Vorübergehendes. … Sie selbst ist kein Werk (Ergon), sondern eine Thätigkeit (Energeia).

Language, grasped in its true essence, is something continually and at every moment transient. … It is itself no product (ergon) but an activity (energeia). (German quotations throughout; Japanese and English are L/LAB working translations.)

Hence “the true definition of language can only be a genetic one” (genetisch). The words listed in a dictionary and the rules in a grammar are only the “dead deposit” of a living language. What exists is the act by which a speaker, each time, uses the rules to produce a sentence. This one point still resonates in the twentieth-century work of Chomsky (linguistic competence as a generative rule system).

2. Inner form — what the “form” of a language is

material (Stoff) = common to every language the continuum of sound the continuum of thought inner form (innere Sprachform) language A's cut language B's cut Each language organises the same material by its own "form." The form is not a set of facts but "the pure working of the language faculty" — the constant, characteristic way of turning thought into sound.
The "material" is common to all languages; the "form" that organises it differs from one to the next. This form is later named "inner form." Diagram: L/LAB

What is the “form (Form)” of a language? For Humboldt it is neither the sounds nor the paradigm tables. It is “what is constant in a language” — the way, particular to that language, fixed and characteristic, in which it converts thought into speech. It is “nothing factual and individual” but “the pure working of the language faculty.” Hyman Steinthal and others later tidied this into the term “inner form of language (innere Sprachform).” The “material” — sound and meaning — is common to humankind; the “form” that cuts up that material differs by language, and by people.

3. Every language is a “worldview (Weltansicht)”

speaker of language A inside A's worldview language B's worldview the only way out of the circle is to step, at once, into another one.
"Every language draws a circle around the people to whom it belongs." To learn a foreign language is to move into another circle. Diagram: L/LAB

Jede Sprache zieht um die Nation, welcher sie angehört, einen Kreis, aus dem es nur insofern hinauszugehen möglich ist, als man zugleich in einen anderen hinübertritt.

Every language draws about the people to whom it belongs a circle, from which one can escape only by stepping at the same time into the circle of another. (§9)

Language is not merely a “means of conveying thought.” “Man lives with objects mainly — indeed, since feeling and acting depend on his representations, exclusively — as language brings them to him.” So Humboldt presses on: “Language is, as it were, the outward appearance of the spirit of a people; their language is their spirit, and their spirit is their language; one can never think the two identical enough.” Here is the source of what later became the Sapir–Whorf hypothesis of linguistic relativity.

4. “Infinite use of finite means”

finite means an inventory of sounds words and word-forming rules rules of combination infinite use make, and understand, sentences never uttered before
Language achieves "infinite use of finite means." Chomsky cites this phrase as an anticipation of generative grammar. Diagram: L/LAB

Sie muss daher von endlichen Mitteln einen unendlichen Gebrauch machen, und vermag dies durch die Identität der Gedanken und Sprache erzeugenden Kraft.

It must therefore make infinite use of finite means, and can do so through the identity of the power that generates thought and language. (§13)

From a limited stock of sounds, words and rules, a speaker makes an unbounded number of sentences that have never appeared before, and a hearer understands them. In 1966, Noam Chomsky put this phrase at the head of Cartesian Linguistics and called Humboldt a forerunner of generative grammar — “the creative aspect of language use.”

5. Language is the organ that forms thought, and lives only in dialogue

Language and thought cannot be separated. “Language is the formative organ of thought (Die Sprache ist das bildende Organ des Gedanken).” A word is not “an imprint of the object in itself” but “of the image it produces in the soul.” Thinking depends not on language in general but “on each particular language.”

And that language does not exist for one person alone. “All speaking rests on dialogue (alles Sprechen ruht auf der Wechselrede).” The word “I” is possible only because “thou” is already implied. Language is at once the individual’s and, beyond the individual, the whole people’s — and it is self-active (selbstthätig): the people make the language, and the language forms the spirit of the people.

6. A typology of languages — and its ranking (read critically)

isolatingChinese agglutinatingTurkish inflectingSanskrit incorporatingNahuatl Humboldt's ranking: inflecting languages as "the most complete form" → this ethnocentric ranking is explicitly rejected later by Sapir and others
Humboldt pioneered classifying languages by structure. But his ranking, with inflecting Sanskrit at the top, carries the bias of its era. Diagram: L/LAB

Humboldt also pioneered a typology of languages by structural type: isolating (Chinese), agglutinating, inflecting (Sanskrit), and the incorporating type found in the languages of North America. But he took inflecting languages to realise “grammatical form” most purely, and tacitly ranked them. That view — “the Sanskrit / Greek type is the high-water mark of linguistic development” — took deep root in nineteenth-century linguistics, and was flatly denied in the twentieth by Sapir in chapter 6 of Language: “all languages are formal languages.” Reading Humboldt means separating this ranking from the deep intuition beneath it — that form, not substance, is the essence of language.

In sum

Humboldt’s claimkeyword
The reality of a language is not its dictionary or grammar but the carrying-out of speechenergeia (activity) / ergon (product)
The “form” of a language is the constant way it turns thought into soundinner form (innere Sprachform)
Every language draws a circle around a people = a worldviewWeltansicht / source of linguistic relativity
An infinite set of sentences from finite sounds, words and rulesinfinite use of finite means
Language is the organ that forms thought; it lives in dialogue and is self-activebildendes Organ / Wechselrede / selbstthätig
Languages can be classified by structure (but the ranking of inflecting languages is a period bias)isolating / agglutinating / inflecting / incorporating

Why it is still read

The three later books — Saussure’s Course, Sapir’s Language, Wittgenstein — can each be read as taking up, with different tools, the questions Humboldt posed: language and thought, form and substance, the individual and the community.