Maxwell’s demon, which extracts work from a thermodynamic system by acquiring information about it, has for more than a century been a favorite thought-experiment in the foundations of statistical physics. The demon has variously been viewed as a threat, an exception, an exemplar, and a means for extending the Second Law. I will describe a formulation of thermodynamics in which such “information engines” play the central role, yielding insights about entropy, information erasure, the meaning of temperature, and the connection between fluctuation and dissipation.