Faith ultimately guides the ones that embrace a new paradigm, not proof

paradigm debates are not really about relative problem-solving ability, though for good reasons they are usually couched in those terms. Instead, the issue is which paradigm should in the future guide research on problems many of which neither competitor can yet claim to resolve completely.

A decision between alternate ways of practicing science is called for, and in the circumstances that decision must be based less on past achievement than on future promise.

The man who embraces a new paradigm at an early stage must often do so in defiance of the evidence provided by problem-solving. He must, that is, have faith that the new paradigm will succeed with the many large problems that confront it, knowing only that the older paradigm has failed with a few.

A decision of that kind can only be made on faith.