Along the development of economic theories, this chapter is focused on the representative thoughts and methodologies, including economic thoughts from Adam Smith, Alfred Marshall, Maynard Keynes, Milton Friedmann, Paul Samuelson, and methodological models such as Arrow-Debreu model, Mundell-Fleming model, Cobb-Douglas model, and Solow-Swan model. All the thoughts and models are integrated into a grand synthetic framework for new synthesis. Three basic economic principles, called EME (equilibrium principle, marginal principle, and extremum principle), are proposed for efficiency-equity equilibrium.