It is often argued that constitution and causation are different kinds of metaphysical relations. Constitution, like other grounding relations, is assumed to be synchronic (it happens at a time), while causation is diachronic (it happens over time). It is this synchronic-diachronic division that, more than other difference-makers, is argued to distinguish grounding relations such as constitution from causation. This paper develops an account of a species of constitution that happens over time. We call this type of constitution, diachronic constitution. We show how diachronic constitution is a consequence of a common type of causation, often ignored in metaphysical discussions of causation: continuous reciprocal causation. Hence, constitution is not only sometimes like causation; it can also be a form of causation. We argue that temporalising the constitution relation is neither as remarkable nor as problematic as it might initially seem. It is inevitable, given local interactions between microscale and macroscale states in dynamical systems
