• To reject one paradigm without simultaneously substituting another is to reject science itself.
• What man sees depends both upon what he looks at and also upon what his previous visual-conception experience has taught him to see.
• Its assimilation requires the reconstruction of prior theory and re-evaluation of prior fact, an intrinsically revolutionary process that is seldom completed by a single man and never overnight.

Once it has achieved the status of paradigm, a scientific theory is declared invalid only if an alternate candidate is available to take its place.

• Unless he has personally experienced a revolution in his own lifetime, the historical sense either of the working scientist or of the lay reader of textbook literature extends only to the outcome of the most recent revolutions in the field.

― Thomas S. Kuhn, The Structure of Scientific Revolutions