Quantitative research is regarded the hallmark of modern science because quantification obtained through measurement enabled the successes of physical science. Presuming it could serve as the standard model for all sciences, psychology implemented quantitative methods to 'measure' its study phenomena. In this keynote speech, I will contrast psychometrics—thought to enable the ‘measurement of mind’—with genuine measurement to pinpoint fundamental differences in their underlying philosophy of science. Measurement establishes traceable relations between the empirical study phenomena and the symbolic systems (data) that are used to represent quantitative information about these phenomena. Psychometrics, by contrast, is aimed at discriminating well and consistently between cases (e.g., individuals) and in ways considered important for pragmatic purposes (e.g., social relevance)—yet without establishing traceable relations to the actual study phenomena. These fundamental differences are masked by various challenges that arise from the peculiarities of psychology’s study phenomena—in particular, their abstract nature, non-independency of human mind and the language-based methods that are necessary for their exploration (e.g., rating ‘scales’). These make psychological research prone to various fallacies in which the study phenomena are confused with the means used for their exploration—psychologists’ cardinal error. Using transdisciplinary perspectives, I will elaborate the epistemological foundations and basic methodological principles of measurement and show how these can be used to advance approaches that allow us to obtain traceable and thus, epistemically valid information about human individuals.