This introduction to a special issue of Nonlinear Dynamics, Psychology and Life Sciences discusses the contributing articles within the issue from a variety of perspectives. This analysis examines each article's contribution to understanding the self, and to exploring the application of innovative nonlinear methods to clinical questions. Moving beyond the special issue, the analysis examines the role of nonlinear science in clinical psychology from the perspective of Aristotle's four types of cause: material, efficient, formal and teleological. It is suggested that nonlinear science is particularly well-suited to empirical science aimed at understanding formal (i.e., systemic), and teleological (dynamical) causes. The strength of nonlinear dynamical systems methods in addressing formal and teleological cause could help bridge the gaps in understanding clinical phenomena using the medical model, which focuses primarily on material and efficient causes. Finally, a list of the top ten nonlinear dynamical systems concepts is presented with the goal of direct applications that may be useful for clinicians.