Emergence in Physics

We examine cases of emergent behavior in physics, and argue for an account of emergence based on features of the phase space portraits of certain dynamical systems. On our account, the phase space portraits of systems displaying emergent behavior are topologically inequivalent to those of the systems from which they ‘emerge’. This account gives us an objective sense in which emergent phenomena are qualitatively novel, without involving the difficulties associated with downward causation and the like. We also argue that the role of complexity in emergence has been overstated: emergent behavior can occur in very simple systems, and even when it occurs in complex systems it is the qualitative novelty of that behavior, rather that the complexity of the system, that matters for emergence.