Under the pressure of increasing criticism, Kuhn finally declared himself dissatisfied with the term paradigm and suggested the phrase disciplinary matrix as a substitute. He felt that disciplinary matrix captured two essential meanings of the original term paradigm: a set of agreed-upon problems and solutions that constituted scientific training and a set of preferred values and methods that constituted everyday scientific practice, "normal science." A paradigm provided the warrants for and the methods of "normal science," a phrase that characterized what most scientists did most of the time. Occasionally, however, paradigms or disciplinary matrices altered dramatically. These were periods of revolutionary change.