This rejoinder addresses commentaries by Markon and Bornovalova and colleagues. Markon highlighted challenges associated with determining cause and effect in mechanistic research. He theorized that “weak emergence” may account, in part, for the complex development of personality pathology. Bornovalova and colleagues addressed transactional relations between various phenomena that may influence development of personality pathology over time. In this rejoinder, the authors build upon these commentaries to further highlight challenges associated with identifying true mechanisms in psychopathology. They hypothesize that dynamical systems models, which conceptualize people as systems open to incalculable environmental influences, may provide an alternative approach through which researchers can examine complex mechanisms more accurately. Although such models are nascent in clinical research, particularly in the context of personality disorders, these approaches may provide more nuanced interpretations of mechanisms and may ultimately enrich our understanding of processes underlying the emergence of personality disorders.