The wealth of information carried by the two-dimensional Raman spectra of liquids comes with a price. The signal arises from a mixture of two entirely different mechanisms, each of which reveals its own perspective on intermolecular dynamics. In this paper we analyze the dynamical origins and consequences of both of these mechanisms. By applying an instantaneous-normal-mode formalism to the two-dimensional Raman spectrum of a solution of CS2 dissolved in Xe, we find discernable differences in the specific molecular degrees of freedom and basic symmetries that contribute to each mechanism. We then show how these differences can be exploited to separate these mechanisms experimentally. In particular, we point out how it should be possible to use two-dimensional Raman spectroscopy to measure the explicitly anharmonic contributions to liquid dynamics without obscuring the results by simultaneously measuring the nonlinear coupling of the polarizability to that dynamics. (C) 2003 American Institute of Physics.