The purpose of this paper is to provide a formal semantic analysis for the determinate / indeterminate aspectual contrast exhibited by verbs of manner of motion in Russian (e.g. idti vs. xodit' (walk)). I propose an intensional approach to determinate verbs that is based on the analysis of the English progressive developed by Dowty (1979). Further, I argue that indeterminate aspect constitutes an identity function and that the aspectual restrictions imposed on sentences which contain indeterminate verbs are pragmatic, rather than semantic, in nature.