Short answers, pulled from the story.
Heterodox economics is a broad term for schools of economic thought not commonly perceived as belonging to mainstream economics. There is no absolute definition; it is defined in contrast to the most prominent schools of thought in a given time and place. Groups typically classed as heterodox include the Austrian, ecological, Marxist-historical, post-Keynesian, and modern monetary approaches.
Economist Frederic S. Lee estimated in 2007 that between five and ten percent of American economists were heterodox, drawn from both left and right-wing schools.
Heterodox schools commonly reject the neoclassical assumption that economic agents rationally maximize utility, arguing that social constraints, coercion, and the complexity of real decisions make this model unrealistic. They also challenge the concept of market equilibrium, asserting that micro-economic models rarely capture how real-world markets actually work.
The four frames highlighted as important to heterodox thought are history, natural systems, uncertainty, and power. These reflect a shared emphasis on time as an irreversible process, socially embedded individuals, and the role of institutions and social structures.
In the mid-19th century, Auguste Comte, Thomas Carlyle, John Ruskin, and Karl Marx made early critiques of orthodox political economy. After the neoclassical revolution of the 1870s, heterodox challengers expanded to include the American School, the historical school, and advocates of social credit and other unorthodox monetary theories.
The International Student Initiative for Pluralist Economics is an umbrella network established in response to the exclusion of heterodox economics from most university economics curricula. It connects smaller university groups such as Rethinking Economics to promote pluralism and heterodox approaches in economic education.