  Given a reductive group $G$, we give a description of the abelian category of
$G$-equivariant $D$-modules on $\mathfrak{g}=\mathrm{Lie}(G)$, which
specializes to Lusztig's generalized Springer correspondence upon restriction
to the nilpotent cone. More precisely, the category has an orthogonal
decomposition in to blocks indexed by cuspidal data $(L,\mathcal{E})$,
consisting of a Levi subgroup $L$, and a cuspidal local system $\mathcal{E}$ on
a nilpotent $L$-orbit. Each block is equivalent to the category of $D$-modules
on the center $\mathfrak{z}(\mathfrak{l})$ of $\mathfrak{l}$ which are
equivariant for the action of the relative Weyl group $N_G(L)/L$. The proof
involves developing a theory of parabolic induction and restriction functors,
and studying the corresponding monads acting on categories of cuspidal objects.
It is hoped that the same techniques will be fruitful in understanding similar
questions in the group, elliptic, mirabolic, quantum, and modular settings.
