  We argue that all fermionic states characterized by the (four) velocity not
momentum of the fermion are always occupied by a single fermion. So there is no
fermion number violation whatsoever. The mass of an elementary particle is not
determined by field equations and is quite arbitrary. Though constant in the
free state, interaction may cause a fermion to go from finite to zeromass
state, interpreted as vacuum, and vice versa. We argue that a massless fermion
can't be detected. Since occupation number is not fixed the arguments leading
to the above conclusions cannot be extended to bosons. We calculate scattering
amplitude for a typical process like Rutherford scattering in the light of the
present discussion to show that there is no contradiction with the experimental
results.
