  We put forward a theory on the optical force exerted upon a dipolar particle
by a stationary and ergodic partially coherent light field. We show through a
rigorous analysis that the ensemble averaged electromagnetic force is given in
terms of a partial gradient of the space variable diagonal elements of the
coherence tensor. Further, by following this result we characterize the
conservative and non-conservative components of this force. In addition, we
establish the propagation law for the optical force in terms of the coherence
function of light at a diffraction plane. This permits us to evaluate the
effect of the degree of coherence on the force components by using the
archetypical configuration of Young's two apertures diffraction pattern, so
often employed to characterize coherence of waves.
