Applied systems thinking has evolved since the 1950s through three paradigmatic waves.
- First wave: Authors in the first wave regarded systems as real-world entities, and systems models as representations of reality, so objectivity was important.
- Second wave: Second wave authors emphasised thinking in terms of systems, and the exploration of multiple perspectives. The role of models was to aid mutual understanding and enhance the appreciation of diverse viewpoints on action to be taken.
In the 1980s, first and second wave advocates came into conflict.
- Third wave: Third wave authors, initially working under the banner of Critical Systems|Thinking, argued that the division of the systems research community into two camps was unhelpful, and they advocated Methodological Pluralism – mixing methods from both traditions. Other authors set out to address power relations during interventions – in particular, the practice of exploring value and boundary judgements in projects in order to address conflict and marginalization. This practice came to be called Boundary Critique, and it was eventually integrated with methodological pluralism in a new approach labelled Systemic Intervention.
(Source: Midgley, G., & Rajagopalan, R. (2020). Critical systems thinking, systemic intervention, and beyond. Handbook of Systems Sciences, 1-51.)