  A major objective of lattice QCD is the computation of hadronic matrix
elements. The standard method is to use three-point and four-point correlation
functions. An alternative approach, requiring only the computation of two-point
correlation functions is to use the Feynman-Hellmann theorem. In this talk we
develop this method up to second order in perturbation theory, in a context
appropriate for lattice QCD. This encompasses the Compton Amplitude (which
forms the basis for deep inelastic scattering) and hadron scattering. Some
numerical results are presented showing results indicating what this approach
might achieve.
