Abstract: The conflict between external and internal perspectives in private law is both exaggerated and underplayed. Both external and internal perspectives pay too little attention to how the ‘micro’ level of individual, even bilateral, interaction relates to the ‘macro’ level of society and the law as a whole. We will show that both perspectives overlook the resources they could employ to explain how the micro and macro are connected; in their different ways, external and internal perspectives do not draw out the connection between local simplicity and generalization. By treating law as a complex system, both perspectives could converge on a picture of private law in which locally simple structures of bilateral rights and duties scale up to produce emergent properties at the level of society. We suggest that functionalists should take seriously the moral norms immanent in private law – these norms are central to the functioning of private law as a system. Without these modular components, private law can be intractably complex. Accordingly, we propose an inclusive functionalism, one that takes these moral norms at face value. These moral norms perform a crucial function of managing the otherwise intractable complexity of the interactions between parties governed by private law. We also propose an inclusive internalism, which is more open to functional considerations involving simplicity. Private law must avoid intractable complexity if it is to function properly, and this calls for a simplicity criterion: internalists should look for moral norms that are both simple and generalizable. Resolving private law’s conceptual structure at the middle level focuses debate where it is needed. Important questions about the role of public values and the ultimate grounding of private law remain open and are sharpened by recognizing the role that complexity plays in the way that private law operates as a system.