Recent years have witnessed a surge of interest in congestion control. Unfortunately, the overwhelmingly large design space along with the increasingly diverse range of application environments makes evaluating congestion control protocols a daunting task. Researchers often use simulation and experiments to examine the performance of designs in specific contexts, but this gives limited insight into the more general properties of these schemes and provides no information about the inherent limits of congestion control designs, e.g., which properties are simultaneously achievable. To complement simulation and experimentation, we advocate a principled framework for reasoning about congestion control protocols. We report on our initial steps in this direction, which was inspired by the axiomatic approach from social choice theory and game theory. We consider several natural requirements ("axioms") from congestion control protocols - e.g., efficient resource-utilization, loss-avoidance, fairness, stability, and TCP-friendliness - and investigate which combinations of these can be achieved within a single design. Thus, our framework allows us to investigate the fundamental tradeoffs between desiderata, and to identify where existing and new congestion control architectures fit within the space of possible outcomes. We believe that our results are but a first step in the axiomatic exploration of congestion control and leave the reader with exciting directions for future research.