How Long Is the Coast of Quantum Chemistry? Or, How to Evaluate Density Functional Theory as a Scientific Revolution

ABSTRACT Distinguishing scientific revolutions from normal science is a subjective, conflicting matter, largely because of the lack of a definite, unambiguous definition. However, it is always possible to a priori select a working definition for revolutions, and judge scientific programmes and events accordingly in an unbiased manner. On this premise, using Seeman's 13 criteria test, we evaluated density functional theory (DFT) to check if it can be held as a revolution or not. Our historical and conceptual analysis indicates that DFT is indeed a proper revolution, but only when considered strictly within the subdiscipline of quantum chemistry, and not within the whole chemical discipline. This emphasises the idea that demarcating scientific revolutions is a matter of the size of the analysed scientific domain, with revolutions behaving as self‐similar fractals. Key Points Scientific revolutions usually have imprecise and ambiguous definitions, but working definitions can be selected to demarcate, in principle, revolutions from normal science. Using Seeman's 13 criteria test, density functional theory (DFT) can be taken as a genuine scientific revolution, but only within the subdiscipline of quantum chemistry. This emphasises the idea of distinguishing revolutions not according to their nature, but according to the observational magnifying glass, analogous to self‐similar fractals.