 Ontic pancomputationalism may be questioned on both the empirical and the ontological fronts. On the empirical front, there is little positive evidence to support ontic pancomputationalism. Supporters appear to be motivated by the desire for exact computational models of the world rather than empirical evidence that the models are correct. Even someone who shares this desire may well question why we should expect nature to fulfill it. On the metaphysical front, Pythagoreanism faces the objection that the abstract entities it puts at the fundamental physical level lack the causal and qualitative properties that we observe in the physical world—or at least, it is difficult to understand how abstract entities could give rise to physical qualities and their causal powers (e.g., Martin 1997).