Almost a century lies between Gagnier's biography of Mohammed and that of the Heidelberg professor Weil (_Mohammed der Prophet, sein Leben and seine Lehre_, Stuttgart, 1843); and yet Weil did well to call Gagnier his last independent predecessor. Weil's great merit is, that he is the first in his field who instituted an extensive historico-critical investigation without any preconceived opinion. His final opinion of Mohammed is, with the necessary reservations: "In so far as he brought the most beautiful teachings of the Old and the New Testament to a people which was not illuminated by one ray of faith, he may be regarded, even by those who are not Mohammedans, as a messenger of God." Four years later Caussin de Perceval in his _Essai sur l'histoire des Arabes_, written quite independently of Weil, expresses the same idea in these words: "It would be an injustice to Mohammed to consider him as no more than a clever impostor, an ambitious man of genius; he was in the first place a man convinced of his vocation to deliver his nation from error and to regenerate it." About twenty years later the biography of Mohammed made an enormous advance through the works of Muir, Sprenger, and Nôldeke. On the ground of much wider and at the same time deeper study of the sources than had been possible for Weil and Caussin de Perceval, each of these three scholars gave in his own way an account of the origin of Islâm. Nôldeke was much sharper and more cautious in his historical criticism than Muir or Sprenger. While the biographies written by these two men have now only historical value, Nôldeke's _History of the Qorân_ is still an indispensable instrument of study more than half a century after its first appearance. Numbers of more or less successful efforts to make Mohammed's life understood by the nineteenth century intellect have followed these without much permanent gain. Mohammed, who was represented to the public in turn as deceiver, as a genius mislead by the Devil, as epileptic, as hysteric, and as prophet, was obliged later on even to submit to playing on the one hand the part of socialist and, on the other hand, that of a defender of capitalism. These points of view were principally characteristic of the temperament of the scholars who held them; they did not really advance our understanding of the events that took place at Mecca and Medina between 610 and 632 A.D., that prologue to a perplexing historical drama.