Sterba and Bauer's Keynote Article discusses the blurred distinction between theoretical principles and analytical methods in the person-oriented approach as problematic and review which of the person-oriented principles are testable under the four types of latent variable models for longitudinal data. Although the issue is important, some arbitrariness exists in determining whether a given principle can be tested within each analytic approach. To close the gap between person-oriented theory and methods and to extend the person-oriented approach more generally, it is necessary to embrace both variable-oriented and person-oriented methods because it is not the individual analytic methods but how studies are implemented as a whole that defines the person-oriented approach. Three areas in developmental psychopathology are discussed in which variable-oriented and person-oriented methods can be complementary. The need to better understand the target system using an appropriate person-specific tool is graphically illustrated. Several concepts of dynamic systems such as attractors, phase transitions, and control parameters are illustrated using experimentally perturbed cardiac rhythms (heart rate variability) as an example in the context of translational alcohol research.