Without commitment to a paradigm there can be no science... the study of paradigms is what prepares a student for membership in a particular scientific community. Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice. That commitment and the apparent consensus it produces are prerequisites for normal science, i. e., for the genesis and continuation of a particular research tradition.... scientific revolutions are inaugurated by a growing sense that an existing paradigm has ceased to function adequately in the exploration of an aspect of nature.

p. 11. - The Structure of Scientific Revolutions (1962)