After more than a century of intensive research, the mechanism of the water gas shift reaction continues to be at the epicenter of microkinetic modeling. Recently (L. C. Grabow, A. A. Gokhale, S. T. Evans, J. A. Dumesic, and M. Mavrikakis, J. Phys. Chem. C 2008, 112, 4608-4617) it has been suggested that carboxyl rather than formate routes may be dominant in the water gas shift reaction on Cu. In this presentation we look at the dominant pathways in the water gas shift reaction mechanism via the reaction network approach recently developed by us. More specifically, a microkinetic model involving all of the reaction steps that have been so far proposed in the literature is assembled into a reaction route network. A formal enumeration of all possible pathways in a reaction route network is thus equivalent to the enumeration of all possible walks between two terminal nodes. Quantitatively, the discrimination among routes is performed by employing the direct analogy between the reaction route and electric networks.