Theory of change
An explicit map of how and why a set of activities is expected to produce a desired long-term outcome.
What it means
A theory of change articulates the causal pathway from an intervention to its ultimate goal, working backward from the long-term outcome through the preconditions and intermediate outcomes that must occur, the activities meant to trigger them, and the assumptions and evidence linking each step. Unlike a simple plan, it makes the underlying hypotheses testable and surfaces where a program could break down. It is widely required by funders because it forces designers to state not just what they will do but why it should work and how they will know. Critics warn it can become a tidy diagram that masks weak evidence or rationalizes decisions after the fact. It matters because it converts good intentions into a falsifiable model, aligning stakeholders and defining what to measure at each link in the chain.
Examples
A literacy charity's ToC traces tutoring sessions to improved skills to better grades to higher graduation, naming the assumptions (attendance, family support) each link depends on.
An HR team's theory of change for a wellbeing app runs from downloads to daily use to lower stress to fewer sick days — and exposes the shaky assumption that downloads become use.
A city maps new bike lanes to feeling safer to more cycling to cleaner air, then tests the weakest link first: do lanes actually change how safe riders feel?
First described in Roots in evaluation; Carol Weiss (1995).