  ``Shear softening" refers to the observed reduction in shear modulus when the
stress on an amorphous solid is increased beyond the initial linear region.
Careful numerical quasi-static simulations reveal an intimate relation between
plastic failure and shear softening. The attaintment of the steady-state value
of the shear modulus associated with plastic flow is identified with a
percolation of the regions that underwent a plastic event. We present an
elementary ``two-state" model that interpolates between failed and virgin
regions and provides a simple and effective characterization of the shear
softening.
