The past affects what we are able to do in the present: it creates financial constraints, renders some technical choices feasible (or infeasible), and it shapes organisational cultures, which have significant inertia. Outcomes don’t depend only on current decisions and conditions - they also depend on past outcomes.
Path dependence is a concept from the social sciences, and it plays an important role in safety science. For example, sociologist Diane Vaughan explains the Challenger and Columbia accidents in terms of history: compromises made during the Shuttle program's initial planning stages which created difficult financial and technical constraints, and the organisation’s ‘can-do’ attitude.
Path dependence is also a phenomenon in technology: and both success and failure have historical causes. Understanding path dependence can help us to make sense of our organisations and our systems, and, maybe, make better decisions for now and for the future.