In this chapter is presented the methodological principles that have been applied in modeling economic events. The neoclassical framework is compared with that of Econophysics, and the parallels and conflicts between them are identified. The axioms of modeling economic phenomena are then defined in a new way that is based on the mental character of human beings. Traditionally microeconomic modeling has been based on the decision-making of human beings, and we show that this is analogous with the behavior of a steelyard in physics. On this basis, the principle of modeling in economics is defined that is applied throughout the book.