Paradigm Conversion

Definition

Because rival paradigms are incommensurable, no algorithm settles the choice between them; what decides is a cascade of individual "conversion" experiences that "cannot be forced." Kuhn describes theory choice as rational without being rule-governed: good reasons — problem-solving power, accuracy, fruitfulness, aesthetic appeal like simplicity — operate, but they don't compel agreement, and early adopters must commit "in defiance of the evidence... on faith," because without their commitment the new paradigm never gets developed enough to win on its merits.

In the Book

Kuhn quotes Max Planck's bleak testimony: "a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it." He notes Priestley never accepted oxygen chemistry — not irrational, Kuhn insists, but no longer practicing chemistry by the field's evolving definition — and that early Copernicans converted on the theory's mathematical harmony years before Galileo's telescope supplied further argument. Chapter 8 supplies the precondition: paradigms are abandoned only when a rival candidate exists to replace them, since "to reject one paradigm without simultaneously substituting another is to reject science itself."

Why It Matters

This displaces the assumption that better arguments alone move a resistant community: the practical playbook it implies is to win over early adopters on promise, let their work generate visible wins, and allow results — not memos — to argue for the rest, while recognizing that the most invested skeptics may simply need to be outlasted rather than convinced. It also warns against attacking a failing system without offering a working alternative, since the psychological and social preconditions for abandonment require somewhere to land, not just a proof that the old place is broken.