Driven by a lifelong passion for evolution and complexity, and building on the work of authors such as Butler, Teilhard de Chardin, Putnam, Maturana and Valera, and others, Gerard Jagers became interested in the challenges involved in understanding the past, present and future of the universe. During his second Phd (in Philosophy) he developed the 'operator hierarchy', a modern, science-based version of the classical 'Scala Naturae' theorem. This theory provides a methodological basis for a hierarchical and causal categorization of different types of operators, linking the evolution of the abiotic world with that of the biotic world, and suggesting extrapolations beyond the current horizon of evolution into the emerging era of artificial intelligence and intelligent machines. His philosophical approach is relevant for and applicable in various research domains. For instance, this hierarchy offers an innovative solution to the current difficulties in attempting to define the concepts of'organism' and 'life'. Gerard Jagers received his Master's degree in Wageningen (1986, Cum Laude), his first PhD in Ecotoxicology (Wageningen, 1993) and, seventeen years later, his second PhD in Physics, Mathematics and Informatics (Nijmegen, 2010). He has worked as a senior quest scientist in ecotoxicology/modelling in Denmark (1997-1999) and from 2001-2017 as a team leader and senior scientist at Alterra (Wageningen University and Research). He has authored and/or co-authored more than 100 publications. He is the author/editor of four books: 'The operator hierarchy', 'The pursuit of complexity', 'Evolution and transitions in complexity' and 'ScienceBites'.