Some people asked me what I thought about the relationship between systems thinking and complexity. See the PDF at the end of this post for the full text of what I came up with. Below is a brief overview.
Surface Answer
Emergence and self-organization often come up in searches for the components of systems thinking. These phenomena have an extensive foundation in complexity science.
Deeper Answer
A premise of systems thinking is that by applying it, we can understand
… a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. Wikipedia.
Rules are descriptive. But why do rules operate as they do? One way to answer this question is by drawing from what complexity science tells us about how systems function. Many complex system behaviors are relevant, but the few that I find useful are attractor, emergence, state change, self-organization and stigmergy. It is also useful to think of programs in ecological and evolutionary biological terms. If complexity is to be applied to systems thinking, the joint operation of different complexity concepts needs to be considered.
Cross-cutting Themes
Complex system behaviors touch on three themes that are of interest in systems thinking – pattern, predictability, and how change happens. One can think of a matrix that cross-references whatever complex behaviors are relevant for a system of interest with these three themes.
Evaluation Uncertainty 