  Ludwig Boltzmann (1844–1906) is generally acknowledged as one of the most important physicists of the nineteenth century. Particularly famous is his statistical explanation of the second law of thermodynamics. The celebrated formula \(S = k \log W\), expressing a relation between entropy \(S\) and probability \(W\) has been engraved on his tombstone (even though he never actually wrote this formula down). Boltzmann's views on statistical physics continue to play an important role in contemporary debates on the foundations of that theory.