On November 4th, 2019, Hans-Georg Moeller delivered a presentation on systems theory at the Law School of the University of São Paulo and was interviewed about Niklas Luhmann’s theory of society, with emphasis on issues such as law, politics, and the history of philosophy. Professor Moeller is the author of important books such as Luhmann explained: From souls to systems (Moeller, 2006) and The radical Luhmann (Moeller, 2011), the latter also translated to Japanese and Italian. He also works on Chinese philosophy and is currently Full Professor at the Department of Philosophy and Religious Studies in the Faculty of Arts and Humanities of the University of Macau, China. Throughout the interview, professor Moeller situated Luhmann in the philosophical tradition of German idealism and presented the shift to second-order observation as a crucial aspect of contemporary society, in religion and politics, science, economy and law. The interview was conducted partly in writing and partly in the form of a recorded and transcribed debate.