Normal science does not aim at novelties of fact or theory and, when successful, finds none.

Normal science, the activity in which most scientists inevitably spend most all their time, is predicated on the assumption that the scientific community knows what the world is like. Normal science often suppresses fundamental novelties because they are necessarily subversive of its basic commitments.

Individuals who break through by inventing a new paradigm are almost always either very young men or very new to the field whose paradigm they change. These are the men who, being little committed by prior practice to the traditional rules of normal science, are particularly likely to see that those rules no longer define a playable game and conceive another set that can replace them.

Normal science does not aim at novelties of fact or theory and, when successful, finds none.

All crises begin with the blurring of a paradigm and the consequent loosening of the rules for normal research. .. Or finally, the case that will most concern us here, a crisis may end with the emergence of a new candidate for paradigm and with the ensuing battle over its acceptance.

In science novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation.

Every important idea in science sounds strange at first.