Systems thinking is used to address complex problems and designs. It can be applied in any discipline or practice. Its origins can be traced back 2,500 years at least, to the ancient Greek philosophers.  It is different from but complementary to other ways of thinking like for example scientific reductionism.

 “Systems thinking enables you to grasp and manage situations of complexity and uncertainty in which there are no simple answers. It's a way of 'learning your way towards effective action' by looking at connected wholes rather than separate parts. It's sometimes called practical holism.” Open University¹

A way to characterise Systems thinking is through the essential ideas that are used. These ideas provide a basis for rigor. Blockley and Godfrey² use three key ideas as a framework for Systems thinking ideas: 

1 Open University- Introducing Systems Thinking

2 Blockley D and Godfrey P (2000) Doing it differently, Thomas Telford, London, ISBN 0-7277-2748-6