Comments on an article The Human Being in Society: Psychology as a Scientific Discipline by David Magnusson (2011). This article provides such a much needed rationale for a unifying psychological theory by defining the requirements of a holistic, dynamic, and systemic theory of human individuals to inform psychology as a field and psychological research. The current article debates the question is if and under which circumstances the between-person structure of changes can be identical to within-person changes. This debate highlights that what we believe to know about the relation between two variables such as age and intelligence most often stems from between-person data distributions and may or—more likely—may not describe the relation between two variables within the individual members of the population examined. Similarly, when psychological data of dyads are examined (e.g., Martin et al., 2009), most often between-person distributions of variables in groups of women and men are related, but not within-dyad relations between the same variables. In both cases, a focus on the individual or the individual dyad would necessarily lead to different research questions and research designs. (PsycINFO Database Record (c) 2012 APA, all rights reserved)