 Some of Anscombe’s most influential work was on the nature of causation, a concept which is notoriously difficult to analyze. Part of her motivation for working on causation was to understand human freedom. Her paper “Causality and Determination” [CAD] challenged some of the empiricist orthodoxy of Hume’s account. She is concerned to distinguish causality from determination, arguing that one event can cause another even if the latter isn’t determined by its cause. When we note an event’s cause, we note from what it derived. She writes “Causality consists in the derivativeness of an effect from its causes” (CAD, 136). But that Y derives from X does not entail that X necessitated Y. So, we need not assume that every cause necessitates its effect. If causation always relates types of events (“Whenever an X-like event happens, a Y-like event happens”), then it might look like a cause necessitates its effect. But she challenged the view that the causal relation is actually characterized by constant conjunction of types, and thus whether causation entails necessitation. Discussing Feynman’s Geiger counter case, she writes: