This chapter reiterates the argument against interpreting knowledge of statistical relationships between variables defined only for aggregates of individuals as if it constituted knowledge of the individuals within the aggregates. The chapter reviews key historical developments behind the institutionalization of this problematic interpretive practice, and then explains why attempts to defend those practices by invoking (a) probabilistic thinking and/or (b) practical utility fail. The thesis is re-asserted that knowledge of statistical relationships among variables marking differences between individuals is properly regarded as knowledge of no single one of those individuals—i.e., knowledge of, quite literally, no one—and this is true whether the between-individual differences have been captured by tests, as in correlational studies, or created by investigator-imposed treatments, as in true experiments. The failure to recognize and adjust to this epistemic reality has transformed psychology’s mainstream into a species of demography, and the need to acknowledge and adjust to this reality remains.