 Recall that mathematically, chaos is a property of dynamical systems which are deterministic (§1.2.1). Since the 18th century, the best models of and support for metaphysical determinism were thought to be the determinism of theories and models in physics. But this strategy is more problematic and subtle than has been typically realized (e.g., due to the difficulties with faithful  models, §3.). So perhaps it is not so surprising that some have argued that chaos reflects some form of indeterminism; hence, the world is not metaphysically deterministic. Of course, chaotic systems are notorious for their unpredictability, and some such as Karl Popper (1950) have argued that unpredictability implies indeterminism. Yet this is to identify determinism (an ontological property) with predictability (an epistemic property). 