In the emergence of comparative grammar at the beginning of the 19th century, Sanskrit played a crucial role. The manner in which Friedrich Schlegel (1772–1829) characterized the grammatical structure of this language in his Ueber die Sprache und Weisheit der Indier of 1808 was of great importance for the early phases of development of Indo-European linguistics. As is shown in this paper, the characteristics attributed to Sanskrit derived not only from F. Schlegel’s romantic views on language and literature, but were also influenced by his general philosophical and natural-science views which largely reflected the intellectual climate of the late 18th and early 19th century in Germany. During this period biology, physiology, and comparative anatomy experienced rapid progress, and the ‘organic’ concept of nature they espoused provided cognitive models for other disciplines, notably philosophy (cf. Kant’s Kritik der Urteilskraft of 1790), aesthetics, poetics, and linguistics. These natural-science concepts proved particularly fruitful within the romantic movement; they convinced F. Schlegel to see in Sanskrit a language whose organization resembled most perfectly the ideal Ursprache of Indo-European.