  In this paper, as the second in our series of papers on differential geometry
of microlinear Frolicher spaces, we study differenital forms. The principal
result is that the exterior differentiation is uniquely determined
geometrically, just as grad (ient), div (ergence) and rot (ation) are uniquely
determined geometrically or physically in classical vector calculus. This
infinitesimal characterization of exterior differentiation has been completely
missing in orthodox differential geometry.
