Here is a puzzling phenomenon. Moral theories are typically thought to be necessary. If act utilitarianism is true, for example, then it is necessarily true. However, scientific theories are typically thought to be contingent. If quantum field theory is true, it’s not necessarily true—the world could have been Newtonian. The aim of this chapter is to explore this discrepancy between domains. In particular, it will suggest that necessitism, about both moral and scientific domains, is naturally motivated by `internality’ intuitions. In effect, these internality intuitions tell against the explanatory role of certain `external’ entities—like moral or scientific principles. The chapter suggests that perhaps these internality intuitions are more compelling in the moral case than the scientific case. If so, this would rationalize the combination of moral necessitism and scientific contingentism.