Proving the reality and its characteristics and the possibility of knowledge about it are two necessary preliminary discussions to enter into the main topics of epistemology such as the nature, characteristics, types, limits, tools and sources of knowledge, etc. In this article, we first examine these preliminary issues in Western philosophy and then trace its extension in the philosophy of conventional economics. After that, we explain the viewpoint of Muslim philosophers and also the Qur'anic viewpoint and analyze its results in the knowledge of Islamic economics. Studies show that in the philosophy of conventional economics, the existence of economic reality outside the mind is certain and happens, and in the mainstream of economics, economic reality is considered to be material and the same as natural realities. But the views about the possibility of knowledge have evolved from the possibility of knowledge in a dogmatic way to the possibility of knowledge in a non-dogmatic way and finally to the impossibility of knowledge. From the point of view of Muslim philosophers as well as the Holy Quran, the existence of reality outside the mind and the possibility of knowing it is certain, and according to this, economic reality exists outside the mind in the four fields of religion, system, systematization, and economics, and knowledge of it is also possible. Is. Fateful realities have material and abstract dimensions and are different from natural realities. Economic realities are surrounded by rational and religious social values and mental aspects and they occur within the framework of divine traditions which are the laws of natural development. Activists are involved in the construction of economic reality and have an independent truth from social science researchers.