  One way of arriving at a quantum field theory of electrons and positrons is
to take a classical theory of the Dirac field and then quantize. Starting with
the standard classical field theory and quantizing in the most straightforward
way yields an inadequate quantum field theory. It is possible to fix this
theory by making some modifications (such as redefining the operators for
energy and charge). Here I argue that we ought to make these modifications
earlier, revising the classical Dirac field theory that serves as the starting
point for quantization (putting positrons into that theory and removing
negative energies). Then, quantization becomes straightforward. Also, the
physics of the Dirac field is made more similar to the physics of the
electromagnetic field and we are able to better understand electron spin.
