Lesson 1: Your theory of change

A theory of change is a story about how your actions lead to the outcomes you care about. It’s the causal chain connecting what you do to the impact you want to have. Every effective organisation has one, and you should too.

Here’s why it matters: without a theory of change, you can’t evaluate whether your plan is working. You might feel busy and virtuous—giving money, volunteering, sharing articles—without knowing whether any of it is actually making any difference to the problem you’ve chosen to prioritise.

A personal theory of change has three components. First, the problem you’re targeting—you chose this in Week 4. Second, the pathways through which you’ll contribute to solving it. Third, the assumptions connecting your actions to outcomes.

Consider two people who both want to reduce suffering from factory farming.

Person A becomes a corporate lawyer and donates 10% of their income to The Humane League. Their theory of change: high income leads to large donations, which fund corporate campaigns, which push companies to adopt better welfare standards, which means fewer animals suffer. Each arrow in that chain involves assumptions. Will corporate campaigns keep working? Will The Humane League remain an effective use of funds? Will welfare improvements actually reduce suffering, or just make consumers feel better about consumption?

Person B becomes a food scientist working on cultivated meat. Their theory of change: technical expertise leads to commercially viable alternatives, which leads consumers to switch away from factory-farmed products, which means fewer animals suffer. Different assumptions: will cultivated meat become cost-competitive? Will consumers actually switch? Is the technology even feasible at scale?

Both theories are defensible. Neither is certain. But both are specific enough to test and update. The key question isn’t “which theory of change is right?” It’s “what would have to be true for my theory of change to work?” If you can answer that, you know what to watch for—and when to change course.

This is Week 3’s reasoning-under-uncertainty toolkit applied to your own life. You’re building a model with uncertain parameters, making your assumptions explicit, and identifying the points where you might be wrong. The difference is that the model is about you.