  In the framework of quantum field theory in curved space-time, we study the
quantization of a massless fermion field on a non-extremal Kerr black hole. The
key theme in this note is the fundamental difference between scalar and fermion
fields for the process of defining quantum states. In particular, we define two
new states for fermions on Kerr which cannot be defined for quantum scalar
fields on Kerr. These two states are the analogues of the standard Boulware and
Hartle-Hawking states on a Schwarzschild black hole.
