In 1962, historian and philosopher of science Thomas Kuhn published a book titled The Structure of Scientific Revolutions. Kuhn proposed that paradigms – theoretical frameworks of scientific disciplines within which theories are formulated and experiments performed – can and should change because sooner or later, they fail to explain observed phenomena. According to Kuhn, when anomalies – experimental observation or other empirical evidence which violates the widely accepted theoretical framework – that the paradigm cannot accommodate or accumulate, and persistent efforts by scientists fail to elucidate these anomalies, the scientific community begins to lose confidence in the dominant paradigm and a crisis period ensues. A new paradigm, competing with the old for supremacy, can now be entertained. This new paradigm is not just an extension of the old paradigm, but a completely different worldview.