Abstract
The concept of difference has a long and important research tradition. We identify and explicate a heretofore overlooked distinction in the meaning and measurement of two different meanings of 'difference': 'diversity' and 'heterogeneity'. We argue that ‘diversity’ can describe a population well enough but does not describe a collective well. In contrast, ‘heterogeneity’ describes a collective better than a population and therefore ought to describe a collective. We argue that ignoring these distinctions can lead to a surprising and disturbing conflict between diversity and heterogeneity. In particular, focusing on the 'diversity' of human communities can be self-defeating for those who truly care about the importance of diversity, inclusion, and belonging.