According to Robert Sparling’s account in Johann Georg Hamann and the Enlightenment Project (145), Moses Mendelssohn considered human beings to be isolated individuals. Language is a tool used by these isolated individuals to connect concepts in our head to things in the world. Speech involves assembling little bundles of signs to communicate a message from one head to another. We can’t be sure it succeeds, since we never actually get into another’s head. Mendelssohn was thus an odd mix of rationalism and skepticism.
Just what one would expect, Hamann responded: “Lust for doubting of truth and the credulousness of self-deception are thus just as inseparable symptoms as the chill and the heat of a fever.”
Fundamentally, though, Mendelssohn’s double problem arose from his misconstrual of the place of language in human life. For Hamann, “Language is not a bundle of signs that an isolated individual attaches to some abstracted characteristic he wishes to separate out from his impression of external phenomena. Rather, it is the constitutive basis of existence. God spoke the world into being; the world is a divine message. Man, too, speaks, and, being made in the image of God, his words are both creative and revelatory. . . . Human existence is essentially linguistic and communal. To be a human being is to communicate.” Against Mendelssohn and Hobbes, language is not artifice but essence.
It’s all bound up in Hamann’s motto, “Speak, that I may see you.”