In this book, distinguished professors Mankiw and Taylor present and analyze the material that constitutes the usual content of introductory textbooks of Economic Theory based on two elements: the given institutional framework of the free market and ten principles of economic behavior of individuals. The content of the book is the material taught in Microeconomics and Macroeconomics courses, namely the theory of determining the prices of goods and productive factors, income determination, international trade, the labor market, the public sector, economic development, market forms, financial markets, etc. However, there are also interesting topics not covered in other textbooks, such as: - Arrow's impossibility theorem - Condorcet's paradox - the problem of time inconsistency - the concept of social justice, etc. The book is enriched with: - auxiliary material - numerical and diagrammatic models - case studies of problems - excerpts from the international press - informational texts on topics or persons (Smith, Ricardo). It is an excellent aid for Economic Sciences. An impressive feature is the clarity and completeness of the analysis.