 In the loop quantum gravity program, the area and volume operators have discrete spectra. Thus, like electron spins, they can only take certain values. This suggests (but does not imply) that space itself has a discrete nature, and perhaps time as well (depending on how one resolves the problem of time). This in turn suggests that space does not have the structure of a differential manifold, but rather that it only approximates such a manifold on large scales, or at low energies. A similar idea, that classical spacetime is an emergent entity, can be found in several approaches to quantum gravity (see Butterfield and Isham, 1999 and 2001, for a discussion of emergence in quantum gravity). The possibility that a continuous structure (with continuous symmetries) could emerge from a fundamentally discrete structure is a problem with a clear philosophical flavour —Huggett and Wüthrich, eds. (2013) contains a variety of papers investigating this issue, with their own contribution focusing on the notion of recovering ‘local beables’ from such emergent theories. 