What makes heterodox economic theories heterodox?

“heterodox” is, in my opinion, best thought of in its relationship to orthodox economics. One can make a very successful (nobel prize winning!) career off of overturning consensuses in mainstream economics; indeed, lots of research is precisely motivated by the fact that the authors think someone else is wrong about something. Behavioral economics, stiglitz’s work on information asymmetry, the game theory revolution in industrial organization, and the credibility revolution are all examples of innovations that, at least partially, overturned the existing paradigms.

in those cases, it took some combination of empirics, persistence, and, most importantly, a new theory that was able to replace what was already there. Hence the quote “it takes a model to beat a model”. there’s a longer answer on why certain ideas take off and others don’t, particularly with regard to policy influence.

by and large, however, heterodox economists are not particularly interested in convincing mainstream economists (see, for instance, the cambridge journal of economics). i haven’t done this empirically, but my sense from reading a handful of articles is that the patterns of cross-citation are fairly limited and confined to fairly small subfields of economics (e.g., interest rate effects on output).

in contrast, if you take, for instance behavioral economics or the credibility revolution, those were deeply involved with active, contemporary research and they were trying to change and appeal to orthodox economists.

where there might be competition would be over policymakers and popular opinions about the economy. MMT, for instance, has a secondary interest in convincing economists and a primary interest in convincing politicians and the public, writ large.