What is a human being able to realize, if he is only reliant to his rational abilities? Formulated in a religious context: Is a human being able to gain true knowledge of God, irrespective of tradition and revelation, only by using his own rationality? And above all: How are religion and rationality related to each other?Ever since, these questions make up an important part of Islamic religious philosophy. In the 12th century the philosopher Abu Bakr Ibn Tufail wrote the educational novel “Hayy Ibn Yaqdhan”, making the above mentioned questions, by the use of a philosophical-allegorical narration, subject of discussion.The novel tells of Hayy Ibn Yaqdhan, who grows up alone on a tropical island. Hayy Ibn Yaqdhan acquires knowledge in the field of natural sciences, only by using his own rationality. Subsequently, he uses his gained knowledge to attain true knowledge of God. At the end of the story the protagonist, representing pure rationality, meets Asal, a representative of the revealed religion. By means of this encounter, Ibn Tufail discusses the relationship between religion and rationality.