 To adopt a computing metaphor, the reductionists whom developmental systems theory opposes assume that causal factors can be divided into ‘processes’ and ‘data’, as in the Harvard computer architecture.Data (inputs, resources, content, and so on) is required by all processes, and must often fall within certain limits if the process in question is to have its ‘normal’ outcome.However, the data alone is helpless to create this outcome, while the process may be ‘satisfied’ with a considerable range of alternative data.