Classical electrodynamics has a century-old problem with self-force. A charged particle radiating electromagnetic waves must lose energy, and the equation governing this — the Lorentz-Abraham-Dirac equation — is exact within classical theory. It is also pathological. It admits runaway solutions: a charge that spontaneously accelerates to the speed of light without any external force. It requires pre-acceleration: a charge that begins moving before the force that moves it has arrived. These are not approximation errors or numerical artifacts. They are exact solutions of an exact equation.
The standard response has been to accept the equation and manage its pathologies — perturbative expansions, order reduction, renormalization. The equation is kept; the solutions are filtered. BarAvi (arXiv:2603.11064) takes the opposite approach. The equation is not kept. The object it describes — a point charge — is replaced.
A point charge has no internal structure. Its self-interaction is instantaneous and singular: the field at the charge's location diverges, and the self-force requires infinite subtraction to produce a finite result. The subtraction works, formally, but it strips away information about how the charge actually responds to its own field. A deformable charge — a finite sphere whose internal charge distribution can rearrange — has a self-force with a delay kernel. The field produced at one moment reaches the far side of the charge at a later moment. The retardation is physical, not a regularization trick. It is what electromagnetic self-interaction actually looks like for an object with spatial extent.
In the adiabatic regime, this delay kernel is causal: the self-force depends only on past configurations. Pre-acceleration vanishes because there is no mechanism for it — the charge cannot respond to a field that has not yet reached it. Runaway solutions are suppressed because the high-frequency instabilities that drive them are damped by the internal dynamics. The Schott term — a mysterious energy contribution in the LAD equation that has no obvious physical interpretation — becomes reversible energy stored in the charge's internal deformation. The charge breathes, and the breathing absorbs and releases energy on timescales set by its size.
The LAD equation reappears only in a specific double limit: spatial extent shrinks to zero AND internal dynamics freeze. Both limits must be taken simultaneously. If only the size shrinks but the internal dynamics persist, the self-force remains causal. If only the dynamics freeze but the size stays finite, the retardation remains. The pathologies require both idealizations at once.
This is not the familiar story of regularization, where a divergence is tamed by introducing a cutoff that is later removed. The cutoff here is physical: the charge has a size, and the size does work. Removing it does not refine the answer. It changes the answer's qualitative character — from causal to acausal, from stable to unstable, from mechanically interpretable to formally exact but physically opaque. The point charge is not a simplification of the deformable charge. It is a different object that shares a limiting value.
The pathologies of classical radiation reaction are not in the physics. They are in the portrait.