  Stress-energies for Fermi fields are derived from the principle of general
covariance. This is done by developing a notion of Lie derivatives of spinors
along arbitrary vector fields. A substantial theory of such derivatives was
first introduced by Kosmann; here I show how an apparent conflict in the
literature on this is due to a difference in the definitions of spinors, and
that tracking the Lie derivative of the Infeld-van der Waerden symbol, as well
as the spinor fields under consideration, gives a fuller picture of the
geometry and leads to the Fermion stress-energy. The differences in the
definitions of spinors do not affect the results here, but could matter in
certain quantum-gravity programs and for spinor transformations under discrete
symmetries.
