Heinrich Hertz has for some time attracted the attention of philosophers of science who are interested in the impact of his highly abstract Principles of Mechanics. Yet he has not until recently been much investigated by historians of physics, who, in considering electrodynamics, have for the most part concentrated on figures such as Kelvin, Maxwell, or Lorentz. There is a nice symmetry between the philosophers' interest and the historians' lack of it, because both interests exhibit a long-standing concern with figures who were deeply engaged in the production of new theories or who developed influential abstractions. Hertz himself never did produce a theoretical system comparable to Maxwell's or to Lorentz's, but he did generate an elaborate scheme for the foundations of mechanics that had a substantial impact on foundational thinking in late 19th and early 20th century philosophy.