The tale type index was criticized by Vladimir Propp of the Formalist school of the 1920s for ignoring the of the motifs by which they are classified. Furthermore, Propp contended that using a "macro-level" analysis means that the stories that share motifs might not be classified together, while stories with wide divergences may be grouped under one tale type because the index must select some features as salient. He also observed that while the distinction between animal tales and tales of the fantastic was basically correct—no one would classify "Tsarevitch Ivan, the Fire Bird and the Gray Wolf" as an animal tale because of the wolf—it did raise questions because animal tales often contained fantastic elements, and tales of the fantastic often contained animals; indeed a tale could shift categories if a peasant deceived a bear rather than a devil.