Lawrence Berkeley National Laboratory

We review the current status of understanding of the equation of motion of an electron. Classically, a consistent, linearized theory exists for an eletron of finite extent, as long as the size of the electron is larger than the classical electron radius. Nonrelativistic quantum mechanics seems to offer a fine theory even in the point of particle limit. Although there is as yet no convincing calculation, it is probable that a quantum electrodynamical result will be at least as well-behaved as is the nonrelativistic quantum mechanical results.