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.

The decision to reject one paradigm is always simultaneously the decision to accept another, and the judgment leading to that decision involves the comparison of both paradigms with nature and with each other.

Political revolutions aim to change political institutions in ways that those institutions themselves prohibit. Their success therefore necessitates the partial relinquishment of one set of institutions in favor of another, and in the interim, society is not fully governed by institutions at all

Probably, the single most prevalent claim advanced by the proponents of a new paradigm is that they can solve the problems that led the old one to a crisis.

Rather than being an interpreter, the scientist who embraces a new paradigm is like the man wearing inverting lenses.

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

The historian of science may be tempted to exclaim that when paradigms change, the world itself changes with them.