Kant’s categorical imperative states: “Act only according to that maxim whereby you can at the same time will that it should become a universal law.” Game Theory has recently borrowed this idea from moral philosophy to introduce a new driver in strategic decisions — a motivation that adds cooperation to selfish reasoning. This paper presents a model describing the dynamics of a population whose strategies evolve not only from selfish gain, as in the replicator dynamics, but also from a moral inclination toward cooperation. We apply our model to well-known game-theoretic problems.