How did Johann Gottfried von Herder connect the development of language with the development of thought?

In the philosophy of language, Johann Gottfried von Herder challenged the prevailing rationalist view that language was merely a tool invented by already-rational beings to express pre-existing thoughts. Instead, he argued that language and human rationality developed together as an indivisible process.1

Herder posited that language is the essential medium through which knowledge is possible. He suggested that while humans experience the world through feeling (Gefühl), these experiences remain dim and undifferentiated until they are designated by language. Through the act of reflection (Besonnenheit), humans "break off" or isolate specific aspects of their experience, and the word—acting as both sound and significance—crystallizes these into objective meaning.2

Consequently, Herder viewed language not as a secondary expression of thought, but as the very means of thought itself. By linking the development of communication to the development of human consciousness, he established that the structure of a language serves as a true image of human nature, reflecting the unique sensitivities and outlook of its users.12