Theory of change

A diagram becomes a theory only when it makes its assumptions visible enough to be tested.

Farmer Field Schools offer a useful caution. The approach has been implemented across many countries to build farmers' knowledge through group-based, experiential learning. Systematic review evidence has found gains in knowledge and changes in practice among participants, with more mixed evidence for wider diffusion and some longer-term outcomes. The activity - running a school - was clear.

Whether it changed productivity, income, pesticide exposure or the behaviour of non-participants depended on a chain of assumptions that varied by context.

A Theory of Change makes that chain explicit. Carol Weiss popularised the approach in evaluation as a way to surface the theories, often hidden, through which programmes expect activities to produce outcomes. It asks not only what will be done, but why those actions should influence particular people, institutions or systems and under which conditions.

The basic elements are familiar: a problem or opportunity, the context, actors, activities, outputs, short- and longer-term outcomes, intended impact, assumptions and external factors. Their value lies in the logic connecting them. Training is an activity. Attendance is an output. Knowledge may be an immediate outcome. Adoption, performance and wellbeing are later outcomes.

Each step requires a behavioural or institutional explanation.

Assumptions are therefore not a footnote. Farmers may need access to finance before knowledge becomes adoption. Adoption may need secure tenure before it becomes long-term investment. Higher yield may need a viable price before it becomes income. A company may assume that suppliers will report grievances without retaliation or that local services can respond to referrals.

When assumptions remain implicit, failure is often blamed on implementation even when the causal logic was weak.

A Theory of Change should also distinguish contribution from attribution. In complex settings, several actors and external forces influence the outcome. A company programme may contribute to lower deforestation while law enforcement, commodity prices, weather and community action also matter.

The theory should identify the organisation's plausible contribution and the evidence needed to assess it, rather than claim sole credit for changes it did not control.

Context makes the theory conditional. The same intervention can work differently depending on market access, social norms, institutional trust, land tenure or climate exposure. A theory that is valid in one origin may fail in another because a key assumption does not hold. Replication should therefore reproduce the mechanism and enabling conditions, not merely the activity.

The order of design matters. Weak theories are often constructed after a programme has been chosen, turning the exercise into a narrative that justifies existing activities. A stronger process begins with the outcome and the system producing the problem. It asks which changes are necessary, which actor can influence them and whether the proposed intervention reaches a meaningful leverage point.

Evidence should be attached to the links, not only to the end of the diagram. Research may support some causal steps while local data or stakeholder knowledge support others. High-risk assumptions should be tested early. Monitoring should then track whether the pathway is unfolding: not just how many activities occurred, but whether the expected responses and intermediate outcomes appeared.

The theory must remain revisable. If farmers attend training but do not adopt, the response should not automatically be more training. The team should examine whether the constraint was knowledge, labour, risk, cash, tenure, trust or the relevance of the recommendation. Updating the theory is evidence of learning, not an admission that planning failed.

A Theory of Change is therefore a management and accountability tool before it is a graphic. It improves programme design, focuses monitoring, clarifies claims and creates a common basis for disagreement. Its central discipline is simple: every arrow is a proposition about the world, and every proposition should be open to evidence.

Practical application

For a programme intended to improve farmer income, begin with the income outcome and work backwards. Specify which households are targeted, which sources of income can change, what constraints prevent change, who controls those constraints and why the proposed action is expected to influence them. State assumptions about price, labour, farm size, adoption, market demand and household control of revenue.

Choose indicators at several points in the pathway and establish decision rules. If knowledge rises but adoption does not, what will be investigated? If yield rises without net income, which assumption failed? The Theory of Change should tell the team what to learn and when to change course.

Why it matters

Sustainability programmes operate in complex systems where activities can be delivered successfully without producing the intended outcome. Theory of Change provides the bridge between intention and evidence, making causal claims more proportionate and helping organisations distinguish implementation failure from flawed assumptions.

Common misconception

A Theory of Change is often treated as a sequence of boxes and arrows linking activities to impact. The diagram is only a representation. The theory consists of the causal mechanisms, assumptions, context and evidence that explain why movement between the boxes should occur.

Connections

Systems thinking describes the wider structure, feedback and leverage surrounding a problem. Theory of Change defines the particular pathway through which an intervention expects to contribute. Materiality then determines which sustainability matters and outcomes are significant enough to shape decisions and reporting.

A question worth asking

Which arrow in your organisation's Theory of Change rests on the weakest evidence or strongest assumption, and what would you do differently if that link did not hold?

Selected references

- Weiss, C. H. 1995. Nothing as Practical as Good Theory: Exploring Theory-Based Evaluation for Comprehensive Community Initiatives.

- Vogel, I. 2012. Review of the Use of Theory of Change in International Development. UK Department for International Development.

- Waddington, H. et al. 2014. Farmer Field Schools for Improving Farming Practices and Farmer Outcomes: A Systematic Review. Campbell Systematic Reviews 10(6).

- United Nations Development Group. 2017. Theory of Change: UNDAF Companion Guidance.

- Rogers, P. 2014. Theory of Change. UNICEF Methodological Briefs: Impact Evaluation No. 2.