One essential element of Chisholm’s view is the idea that there is a distinction between event causation and agent causation. In cases exclusively involving event causation, everything that causally contributes to an event is another event. In cases involving agent causation, among the things that causally contribute to an event is a person. In virtue of this feature, Chisholm’s view is generally categorized as a form of libertarianism. Another essential element of his view is the idea that when a person acts freely, he does something for which there is no event or state or combination of events or states that is a sufficient causal condition for his doing it. (There is also no event or state that is a sufficient causal condition for his failing to do it, obviously.) In virtue of this feature of his view, it may be seen as incorporating an element of indeterminism.