Ibn al-Nafis
As the title of "Doubts on Galen" by al-Rāzi implies, as well as the writings of physicians such as Ibn Zuhr and Ibn al-Nafis, the works of Galen were not accepted unquestioningly, but as a challengeable basis for further inquiry. A strong emphasis on experimentation and empiricism led to new results and new observations, which were contrasted and combined with those of Galen by writers such as al-Rāzi, Ali ibn Abbas al-Majusi, Abu al-Qasim al-Zahrawi, Ibn Sina (Avicenna), Ibn Zuhr and Ibn al-Nafis. For example, Ibn al-Nafis' discovery of the pulmonary circulation contradicted the Galenic theory on the heart.