Geiger defended Muhammad against a dismissive European scholarly tradition.

Evidence

Since the Enlightenment, many scholars had dismissed Muhammad as a hypocrite and deceiver (Voltaire) and a fanatic (Herder), while the great nineteenth-century Semiticist, Theodor Nöldeke, spoke for many when he referred to the founder of Islam as “hysterical.” Geiger declared such opinions to be the product of “outright bias and misunderstanding of the human heart” [einseitigkeit und gänzlicher Verkennung des menschlichen Herzens]. By contrast, Geiger saw Muhammad as a “genuine enthusiast [wirklicher Schwärmer] who was himself convinced of his divine mission, and to whom the union of all religions appeared necessary for the welfare of mankind.” — Ivan Davidson Kalmar, Derek Penslar, Orientalism and the Jews, 373