Humboldt’s book turns on two “inseparabilities”: that of language and thought, and that of language and the other.

1. Language is the organ that forms thought

object an "image (Bild)" produced in the soul word the word is not a direct imprint of the object (the dotted route is not taken)
An object first produces an "image" in the soul. The word is an imprint of that image, not of the object itself. Diagram: L/LAB

Language is not a tool for “conveying” thought. It is the organ that makes it.

Die Sprache ist das bildende Organ des Gedanken.

Language is the formative organ of thought. (German quotations throughout; Japanese and English are L/LAB working translations.)

And a word is not a label on an object.

Das Wort ist also nicht ein Abdruck des Gegenstandes an sich, sondern des von diesem in der Seele erzeugten Bildes.

The word is thus not an imprint of the object in itself, but of the image produced from it in the soul.

Object → image in the soul → word. It is this middle term (the image) that makes the “elephant” example of the previous piece work: with the same object, a different image grasped gives a different word. Thought becomes distinct (deutlich) only through language — a vague notion gets its outline by being bound to articulated sound. The articulation of sound and the articulation of thought run in parallel.

2. “I” contains “thou”

I thou address (Anrede) reply (Erwiederung) the word "I" already presupposes a "thou"
Speaking consists of address and reply. So a "duality" of first and second person is built into language at its root. Diagram: L/LAB

Language is not completed inside an isolated individual. “All speech rests on dialogue (Wechselrede)” — Humboldt put this most sharply in his essay Über den Dualis (1827). Speaking always consists of address (Anrede) and reply (Erwiederung). So the first person “I” already contains the second person “thou” that hears it. The grammatical dual (a form that singles out “two” of the second person) is, on Humboldt’s reading, a trace of this root duality of language. Speech is turned toward the other from the start.

3. Self-active — between the individual and the community

Language stands above this duality in turn. It is the individual’s — there is no language without the working of one speaker’s mind. It is at the same time the whole people’s — one person can neither make nor change a language. And, owned by neither, it is self-active (selbstthätig): the people form the language, and the language forms the people’s spirit. This aspect — “a social fact that confronts each speaker as given” — is later rebuilt with different tools by Saussure as “langue” and by Wittgenstein as “a rule cannot be followed privately”.

In sum

Humboldt’s claimrestated
Language is the organ that forms thoughtnot a tool for conveying thought, but what makes it
A word is an imprint of “the image in the soul,” not of the objectobject → image → word (there is a middle term)
Thought becomes distinct only through languagethe articulation of sound and of thought run in parallel
All speech rests on dialogue; “I” contains “thou”speech is turned toward the other at its root (Über den Dualis, 1827)
Language is both the individual’s and the community’s, and self-active→ Saussure’s “langue,” Wittgenstein’s “rule”

Why it is still read

The Humboldt feature: overview / energeia / inner form / worldview / infinite use of finite means / this essay / typology and ranking.