Its assimilation requires the reconstruction of prior theory and re-evaluation of prior fact, an intrinsically revolutionary process that is seldom completed a single man and never overnight

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

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.

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

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.

As in political revolutions, so in paradigm choice--there is no standard higher than the assent of the relevant community. To discover how scientific revolutions are effected, we shall therefore have to examine not only the impact of nature and of logic, but also the techniques of persuasive argumentation effective within the quite special groups that constitute the community of scientists.