  Schr{\"o}dinger-Pauli (SP) theory is a description of electrons in the
presence of a static electromagnetic field in which the interaction of the
magnetic field with both the orbital and spin moments is explicitly considered.
The theory is described from a new perspective, viz. that of the individual
electron via its equation of motion or `Quantal Newtonian' first law. The law
leads to new physical and mathematical insights into the theory. The law is in
terms of `classical' fields whose sources are quantum mechanical expectation
values of Hermitian operators taken with respect to the system wave function.
The law states that each electron experiences an external and an internal
field, the sum of which vanish. The external field is the sum of the
electrostatic and a Lorentz field. The internal field is a sum of fields: the
electron-interaction, differential density, kinetic, and internal magnetic
fields. These fields are respectively representative of a property of the
system: electron correlations due to the Pauli exclusion principle and Coulomb
repulsion, the electron density, kinetic effects, and the physical current
density. The energy components can be expressed in integral virial form in
terms of these fields. The law leads to the further understanding that the
Hamiltonian is an exactly known and universal functional of the wave function.
This allows for the generalization of the SP equation, which then proves it to
be intrinsically self-consistent. A Quantal density functional (local effective
potential) theory of the SP system is developed. Further generalizations of the
present work to the temporal case, and relativistic Dirac theory are proposed.
