<p>This opinion article reflects on the evolving relationship between science, technology, and democracy in the era of sustainability. Drawing from personal experience in renewable energy research, fiscal policy, and environmental observation, it examines how scientific authority increasingly intersects with political and ethical domains. While concepts such as the circular economy and energy transition promise a cleaner future, their implementation often overlooks physical, economic, and material constraints. Through examples from Switzerland and beyond, this paper argues that clean technologies and environmental policies must remain grounded in empirical realism and respect for the democratic process. When science assumes the role of moral or political arbiter, it risks losing the intellectual freedom that made it powerful in the first place. Echoing Richard P. Feynman, the perspective concludes that the strength of science rests not in its authority to command, but in its freedom to question. Sustainable progress depends on both technological innovation and the preservation of that freedom to doubt.</p> Graphical abstract <p></p>