Wehler's work has been criticized. From the right, Otto Pflanze claimed that Wehler's use of such terms as "Bonapartism", "social imperialism", "negative integration" and "Sammlungspolitik" ("the politics of rallying together") went beyond mere heuristic devices and instead become a form of historical fiction. The German conservative historian Thomas Nipperdey has argued that Wehler presented German elites as more united than they were, focused too much on forces from above and too little on forces from below in 19th-century German society and presented too stark of a contrast between the forces of order and stabilization and the forces of democracy with no explanation for the German Empire's relative stability. Nipperdey thinks that Wehler failed to explain how the Weimar Republic occurred since Wehler considered that prior to 1918, the forces of authoritarianism were so strong and those of democracy so weak. In a 1975 book review of Wehler's "Das Deutsche Kaiserreich", Nipperdey concluded that a proper history of the German Empire period must be written by placing German history in a comparative European and trans-Atlantic perspective, which might allow the end of "our fixation on the struggle with our great-grandfathers".