19th century in science Carnot captured some of the ideas of thermodynamics in his discussion of the efficiency of an idealized engine. Sadi Carnot's work provided a basis for the formulation of the first law of thermodynamics—a restatement of the law of conservation of energy—which was stated around 1850 by William Thomson, later known as Lord Kelvin, and Rudolf Clausius. Lord Kelvin, who had extended the concept of absolute zero from gases to all substances in 1848, drew upon the engineering theory of Lazare Carnot, Sadi Carnot, and Émile Clapeyron–as well as the experimentation of James Prescott Joule on the interchangeability of mechanical, chemical,
19th-century philosophy positivism, Marxism and philological analysis of the Bible. In the second half of the 19th century, an even more orthodox return to Kantian thought was espoused by a number of Neo-Kantian philosophers based in two main locations: the Marburg School and the Baden School. This trend of thought survived into the beginning of the next century, influencing 20th century philosophical movements such as Neopositivism and Phenomenology. One of the most famous opponents of idealism in the first half of the German 19th century was Ludwig Feuerbach, who advocated materialism and atheism. In early 19th century Britain, Jeremy Bentham and John