Mach's Wärmelehre published in 1896, was an attempt to derive a "clean" version of the theory of heat by freeing its concepts from the accumulation of historically conditioned attitudes and metaphysics. Having written the history of mechanics in its conceptual development, Mach then set out to do the same for the theory of heat, which had a still more complicated history. His philosophical heroes in this quest for clarity were Fourier, Kirchhoff, Joseph Black, Sadi Carnot, Robert Mayer, and William Thomson. Rudolf Clausius would also be included on this list but for the fact that Mach found his mathematical formulations artificial and misleading. As one reviewer pointed out, Mach also, strangely, did not include the classic work of J. Willard Gibbs in his review, which one would think belonged there.