As a successful diplomat between 1802 and 1819, Humboldt was plenipotentiary Prussian minister at Rome from 1802, ambassador at Vienna from 1812 during the closing struggles of the Napoleonic Wars, at the congress of Prague (1813) where he was instrumental in drawing Austria to ally with Prussia and Russia against Napoleon; a signer of the peace treaty at Paris and the treaty between Prussia and defeated Saxony (1815), and at the congress at Aachen in 1818. However, the increasingly reactionary policy of the Prussian government made him give up political life in 1819; and from that time forward he devoted himself solely to literature and study. Linguist Wilhelm von Humboldt was an adept linguist and studied the Basque language. He translated Pindar and Aeschylus into German. Humboldt's work as a philologist in Basque has had more extensive impact than his other work. His two visits to the Basque country resulted in Researches into the Early Inhabitants of Spain by the help of the Basque language (1821). In this work, Humboldt endeavored to show by examining geographical placenames that at one time a race or races speaking dialects allied to modern Basque extended throughout Spain, southern France and the Balearic Islands; he identified these people with the Iberians of classical writers, and further surmised that they had been allied with the Berbers of northern Africa. Humboldt's pioneering work has been superseded in its details by modern linguistics and archaeology, but is sometimes still uncritically followed even today. He was elected a member of the American Antiquarian Society in 1820, and a Foreign Honorary Member of the American Academy of Arts and Sciences in 1822. Humboldt died while preparing his greatest work, on the ancient Kawi language of Java, but its introduction was published in 1836 as The Heterogeneity of Language and its Influence on the Intellectual Development of Mankind. His 1836 book on the philosophy of speech introduces the concept of "the inner form of language" (according to Encyclopædia Brittanica 1911): [F]irst clearly laid down that the character and structure of a language expresses the inner life and knowledge of its speakers, and that languages must differ from one another in the same way and to the same degree as those who use them. Sounds do not become words until a meaning has been put into them, and this meaning embodies the thought of a community. What Humboldt terms the inner