This chapter shows that early modern metaphysics was far more important for Pufendorf’s moral philosophy than has often been thought. In particular, it is essential to understanding Pufendorf’s theory of moral entities. This theory is often regarded as voluntarist and anti-metaphysical. Opposed to this, it has been argued, was a rationalist belief in objective and eternal moral values that was exemplified by philosophers like Leibniz. However, the main distinction for Pufendorf was not between voluntarism and rationalism, but between moral rules that were specific to a certain society because they were merely conventional, and others that were universal because they were natural, in the sense of being grounded in the physical characteristics of human nature as it had been created by God. The latter, according to Pufendorf, were necessarily true, though their necessity was hypothetical rather than absolute. Pufendorf’s intention was to turn moral philosophy into a science, which would supersede traditional Aristotelian-scholastic views that morality was concerned with the contingent circumstances of actions, and therefore incapable of ‘scientific’, that is syllogistic proof. Pufendorf’s theory of moral entities was central to this project of a moral science, which required him to provide a metaphysical foundation for these entities.