We point out that complexity science is developing fast and that present and future scientific and societal challenges will need fundamental improvements in our ability to analyse and deal with complex emergent behaviour. It is therefore desirable to spread widely the awareness of approaches and insights from complexity science.

Conceptual and mathematical models can serve many purposes. We will discuss why simple stylistic models are particularly useful in complexity science since they can help to identify the most essential mechanisms amongst the profusion of interdependencies at play.

When interactions between individual dynamical components are sufficiently strong, coordinated dynamics at the systemic level can emerge. This is called synchronisation.

The third force movement, grounded in the principles of existential philosophy, focuses on the individual in quest of identity, values, and authenticity. The nineteenth century writings of such figures as Kierkegaard, Nietzsche, and Dilthey formed the background for the view of the person as alone and dehumanized. The twentieth century works of Sartre, Camus, and Jaspers offered further expression to the basic state of anxiety and absurdity. The personalism of Emmanuel Mounier and Karol Wojtyła reintroduced the person within psychology. The methodological writings of Husserl and Heidegger contributed to the development of phenomenology as a means of investigating the holistic character of human experience. The combined existential–phenomenological psychology was an application of a new orientation in clinical settings, by such psychologists as Merleau-Ponty and Binswanger. In America, the humanistic viewpoints of Allport, Bühler, Maslow, May, and Rogers agreed generally with the European movement, and a center of existential-phenomenological psychology emerged at Duquesne University. Although it did not generate a comprehensive alternative to behaviorist formulations, the third force movement has exerted an impact on clinical applications, especially in therapeutic efforts.

The breadth of psychology’s history underscores the importance of learning about the present from the past, and psychology’s past is certainly fascinating. Several approaches to the study of intellectual history, particularly for psychology, are presented, as are some of the major recurring themes that are addressed in the book. Finally, the study of the history of psychology as an area of specialization within the discipline focuses on the resources available for serious pursuit.

We present a few paradigmatic modelling strategies selected due to their generality in addressing the emergence of spatio-temporal structure, including criticality, synchronisation, intermittency, adaptation and forecasting.

Two parallel trends prepared scholars for the investigation of the mind–body relationship so that a model of psychological inquiry could evolve. The first trend was methodological, characterized by the triumph of empiricism. Scientific innovations by Francis Bacon and Newton were firmly based on careful observations and quantification of observables. Using inductive methods, moving from observed particulars to cautious generalization, empiricism stood in contrast to the deductive methods of the Scholastic philosophers. The second trend occurred in the attempt to develop conceptions on the nature of humanity and was more a philosophical enterprise. Spinoza taught that mind and body are manifestations of the same unity of the person. Human activity, although unique because of humanity’s higher intellectual powers, is determined by the laws of nature. Descartes stated that the first principle of life is self-awareness of the idea, and all else that we know proceeds from self-reflection. His dualism of the interaction between mind and body distinguishes psychology from physiology. Descartes’ views were developed in the French and British philosophical traditions; Spinoza influenced the German efforts to develop a model of psychology.