by Ayatullah Ibrahim Amini (Author), Sayyid Athar Husain S. H. Rizvi (Translator)
Islamic subjects and problems can be divided into two groups: Principles of faith (Usul Deen) and secondary issues (Furu Deen). Principles of faith (Usul Deen) are also called as beliefs and secondary issues (Furu Deen) are known as duties.