The history of science is the study of the development of science and scientific knowledge, including both the natural and social sciences (the history of the arts and humanities is termed history of scholarship). Science is a body of empirical, theoretical, and practical knowledge about the natural world, produced by scientists who emphasize the observation, explanation, and prediction of real-world phenomena. Historiography of science, in contrast, studies the methods employed by historians of science. The English word scientist is relatively recent—first coined by William Whewell in the 19th century. Previously, investigators of nature called themselves "natural philosophers". While empirical investigations of the natural world have been described since classical antiquity (for example, by Thales and Aristotle), and the scientific method has been employed since the Middle Ages (for example, by Ibn al-Haytham and Roger Bacon), modern science began to develop in the early modern period, and in particular in the scientific revolution of 16th- and 17th-century Europe. Traditionally, historians of science have defined science sufficiently broadly to include those earlier inquiries.From the 18th through the late 20th century, the history of science, especially of the physical and biological sciences, was often presented as a progressive accumulation of knowledge, in which true theories replaced false beliefs. More recent historical interpretations, such as those of Thomas Kuhn, tend to portray the history of science in terms of competing paradigms or conceptual systems within a wider matrix of intellectual, cultural, economic and political trends. These interpretations, however, have met with opposition for they also portray the history of science as an incoherent system of incommensurable paradigms, not leading to any actual scientific progress but only to the illusion that it has occurred.