Thomas Samuel Kuhn
A historian of science (1922–1996) who was concerned with the laws governing development and scientific progress. He demonstrated that the concept of science as a regularly progressing process refining our knowledge is basically erroneous. He showed that three phases alternate in science. The phase of normal science is usually longest; here, slow development and refinement and elaboration of existing theories actually occur. This is followed by the phase of crisis science, when it is found that an ever increasing number of facts don’t fit into the existing theory. The third phase is a scientific revolution, when the old theory is rejected and replaced by a new theory. The previous period and the previous theory are then forced out of the textbooks and subsequently from the consciousness of the relevant scientific community and, after some time, the history chapters of textbooks are rewritten as if the new theory had existed throughout all time. A new comfortable period of normal science begins. According to Kuhn, the main reason for this discontinuous development of science is the existence of paradigms – assumptions on which the accuracy of the theory stands or falls. However, during the period of normal science, scientists are not even aware of the existence of the paradigm and thus do not think about or test its validity.