One of the main issues in the philosophy of any science, including the economics, is epistemology or the theory of knowledge. During the new era and with Kant’s Copernican Revolution, new dimensions are added to the theory of knowledge, and they have consequently affected the philosophy of social and natural sciences. Despite the fact that the philosophy of science, epistemology, and methodology have been widely developed during the twentieth century, economics has not paid much attention to these issues in practice, even though, a few journals have been published in this regard since the 1980s. Such an ignorance might be the result of the dominance of neoclassical paradigm as the mainstream in economics. The neoclassical paradigm is based on the reductive concept of economic reality, which considers the positive method to be sufficient for knowledge achievement. With the emergence of econometric revolution and the dominance of quantitative perspectives in economics, the concepts of the philosophy of economics, including epistemology, practically seemed to be redundant. In this book, it is shown that the dominance of a quantitative perspective and a positive method in the neoclassical paradigm of economics lead to an incomplete understanding of economic reality.