 As may already be clear, the accounts of the underlying mechanisms are individual-level accounts in the sense that they invariably contain descriptions of what happens to, and what is made to happen by, individuals. It is standard to invoke descriptions of individuals by reference to their roles and other properties they possess as a result of being part of social organizations. In this sense, a permissive notion as to what counts as individual-level descriptions is endorsed. The accounts of individuals may draw on different theories of the actor. In earlier phases of the debate, there was a clear tendency to base the accounts on rational-choice models. Today, other models are used as well.