Apart from the 20-year anniversary in 2014 of the first publication of the GERAM ('General- ised Enterprise Reference Architecture and Methodology') Enterprise Architecture Framework, the time- liness of this paper lies in the new interest in the use of systems theory in Enterprise Architecture (EA), and consequently, 'light-weight' architecture frameworks (AFs). Thus, this paper is about the use of sys- tems thinking and systems theory in EA and about how it is possible to reconcile and understand, based on a single overarching framework, the interplay of two major enterprise change endeavours: on the one hand enterprise engineering (i.e. deliberate change) and on the other hand evolutionary, organic change. The paper also attempts to show how such change processes can be illustrated by employing systems thinking to construct dynamic business models: the evolution of these concepts is exemplified with some past applications in networked enterprise building and more recent proposals in environmental, disaster and healthcare management. Finally, the paper attempts to plot the way GERAM will continue to con- tribute to society in the context of future challenges and emerging opportunities.