Abstract

In Leo Szilard’s 1929 thought experiment, a Maxwell demon manipulates a one-molecule gas to reverse the second law of thermodynamics. The demon must fail, Szilard argued, since there is hidden entropy creation in the demon’s collecting of information. This thought experiment is an inconsistent muddle of improper idealizations. It diverted an already successful literature of exorcism into degenerating speculations about about a connection between thermodynamic entropy and information. These confusions persist today in a voluminous literature. Narrative conventions in a thought experiment allow thought experimenters great latitude in deciding which processes are typical and bear generalization and which can be idealized away as incidental. For its abuse of this latitude and the extent of the harm it caused, this thought experiment merits the distinction of the worst thought experiment in science.