 The core of Wheeler and Feynman’s proposed “absorber theory of radiation” is a suggestion that the process of electromagnetic radiation emission and absorption should be thought of as an interaction between a source and an absorber rather than as an independent elementary process. (This idea has its roots as far back as Tetrode 1922 and G. Lewis 1926.) Wheeler and Feynman imagine an accelerated point charge located within an absorbing system and consider the nature of the electromagnetic field associated with the acceleration. An electromagnetic disturbance can be imagined “initially” to travel outwards from the source to perturb each particle of the absorber. The particles of the absorber then generate together a subsequent field. According to the Wheeler-Feynman view, this new field is comprised of half the sum of the retarded (forward-in-time) and advanced (backward-in-time) solutions to Maxwell’s equations. The sum of the advanced effects of all the particles of the absorber then yields an advanced incoming field that is present at the source simultaneous with the moment of emission (although see  §5  for more on how one should understand this “process”). The claim is that this advanced field exerts a finite force on the source which has exactly the required magnitude and direction to account for the observed energy transferred from source to absorber; this is Dirac’s radiative damping field. In addition, when this advanced field is combined with the equivalent half-retarded, half-advanced field of the source, the total observed disturbance is the full retarded field known empirically to be emitted by accelerated point charges.