Throughout history, schools of economic thought have defined political economy—or economics—and its object of study in multiple ways. This paper reflects on the definitions of economics by schools of economic thought and also proposes the concepts of value and scarcity as key concepts to explain the differences between them. The most important findings of the paper are: (a) the ontological and epistemological characteristics of the concept of value and scarcity have shaped the definitions of economics; (b) the boundaries of the (...) study object of economics have been expanded since today’s mainstream economics deals with multiple topics as diverse as crime, education, development, health, etc. However, the methodological tools used in mainstream economics have been narrowed since approaches such as the philosophical, ethical, historical, and institutional approaches have been left behind; (c) the part of reality that mainstream economics can grasp have left behind important issues of the contemporary world, such as gender, social, and environmental issues. A clear understanding of the scope and boundaries of economics could help to define more realistic research questions for economic science, and it would help to define new economic paradigms that address the contemporary issues. (shrink)