Scientific advancements in the field of non-equilibrium thermodynamics have shown that social-ecological systems belong to the class of complex adaptive systems, a subset of the class of open dissipative systems. A proper characterization of the mechanism allowing the reproduction and adaptation of these systems requires a distinction between flows metabolized inside the technosphere (secondary inputs produced and consumed by the economy, under human control) and flows exchanged between the technosphere and biosphere (primary flows stabilized by natural processes, outside of human control). Adopting this scientific conceptualization, it becomes evident that in the process of production and consumption of goods and services, only secondary flows can be re-used inside the system (as tertiary inputs). On the contrary, primary flows, which are dependent on the existence of external supply and sink capacity provided by nature, and essential, cannot be recycled. By implication, the societal endorsement of the concept of circular economy today appears analogous to the societal endorsement of the concept of flat Earth in the Middle Ages.