This paper attempts to engage with the established debate on the nature of heterodox economics. However, it starts from the position that previous attempts to classify and identify heterodox economics have been biased towards a priori definition. The paper aims to inform the discussion of the nature of heterodoxy with some empirical analysis. The paper examines survey data collected from a small/medium-sized sample of AHE members on the core concepts in economics. The paper applies factor analysis to the data. It also applies principles of biological taxonomy, and thence cluster analysis to the problem. The paper finds that within the self-identified community of self-identified heterodox economists there is little agreement as to whether members are pluralist, or what their attitude is to the mainstream. Indeed, there is little agreement on any core concepts or principles. The paper argues that there is little structure to heterodox economics beyond that provided by pre-existing (or constituent) schools of thought. Based on this study, heterodox economics appears a complex web of interacting individuals and as a group is a fuzzy set. These results would lead us to question further strict distinctions between heterodox, mainstream and pluralist economists.