Moffett points to humans' use of physical markers to signal group identity as crucial to human society. We characterize the developmental and cognitive bases of this capacity, arguing that it is part of an early-emerging, intuitive socio-physical interface which allows the inanimate world to encode rich social meaning about individuals' identities, and the values of the society as a whole.

Why have core knowledge? Standard answers typically emphasize the difficulty of learning core knowledge from experience, or the benefits it confers for learning about the world. Here, we suggest a complementary reason: Core knowledge is critical for learning not just about the external world, but about the mind itself.

The ability to reason about ignorance is an important and often overlooked representational capacity. Phillips and colleagues assume that knowledge representations are inevitably accompanied by ignorance representations. We argue that this is not necessarily the case, as agents who can reason about knowledge often fail on ignorance tasks, suggesting that ignorance should be studied as a separate representational capacity.