- We propose Participation-Engagement (PAR-EN) as a philosophically based heuristic for prioritizing interventions in comorbid, complex, and chronic psychiatric conditions. Drawing from 1) the sociologist Talcott Parsons, 2) the continental-philosophical tradition, and 3) our own previous work (Davidson & Shahar, 2009; Shahar, 2004, 2006), we argue that participation in personally meaningful life goals represents a hallmark of mental health. Symptoms and vulnerabilities that impede such participation should therefore be targeted vigorously, whereas others which do not pose such imminent threats should assume a secondary focus, if at all. Winnicott's (1987) notion of the spontaneous gesture, the importance of daily activities as reflecting patients' participation, and the dialectics of interpersonal relatedness and self-definition, are introduced as guidelines for implementing PAR-EN. Implications for clinical assessment and the therapeutic relationship are discussed.