Muslims have created great civilizations throughout history; but the Muslim world has experienced a visible decline starting from the 19th century due at least in part to the technological developments in the West. Since then, many of the scientific and economic models that were transferred and implemented in commercial and social life in Islamic countries were mostly against Islamic culture. This is the main reason for the ongoing discussions on whether the notions imported from the Western literature are Islamically acceptable or not. What does an Islamic reference in an economic or social model refer to? This chapter seeks an answer to the question of who is a Muslim and what responsibilities he/she has under Islam in order to distinguish a Muslim individual from a secular one. Hopefully, this will enable us to better explain the differences between the economic models offered by Islam and the secular world, and clarify the conceptual arguments.