Against a more or less categorically fixed understanding of al-Ghazali and ibn Rushd in European discourse that considers the first to be an orthodox theological polemic, the second a rationally orientated freethinker or Aristolelian, the dabate about God's simplicity enables to comprehend the authors more differentiated. It allows glimpses into the complex cosmologies, philosophies and debates important in the 11. and 12. century. Finally it renders al-Ghazali's and ibn Rushd's positions to be quite conciliatory: philosophy and religion, reason and spirit form a harmony; they are closest kins and together allow society to unfold and enlarge its knowledge as well as to preserve its moral constitution.