It is often taken as the very general thesis about the world that all events without exception are effects - events necessitated by earlier events. Hence any event of any kind is an effect of a prior series of effects, a causal chain with every link solid. The thesis is fundamentally simple. The ideas which it contains, notably those of events and causal connection, are certainly open to definition. If the thesis cannot be expressed in terms of some part of science or theory in it, some determinists say, the shortcoming is not in the thesis.