  We describe how multirefence dynamic correlation theories can be naturally
obtained as single-reference correlation theories in a canonically transformed
frame. Such canonically transformed correlation theories are very simple and
involve identical expressions to their single-reference counterparts. The
corresponding excitations involve quasiparticles rather than the bare particles
of the system. High-order density matrices (or their approximations) and the
numerical metric instabilities common to multireference correlation theories do
not appear. As an example, we formulate the Bogoliubov canonically transformed
version of second-order M{\o}ller-Plesset perturbation theory and demonstrate
its performance in hydrogen, water, nitrogen, and BeH$_2$ bond dissociation.
