  Reid develops his account of causation in light of Hume's account. As Reid sees it, Hume starts with the assumption that if we are to learn what causation is, we must first determine from what aspect of our sensory experience the concept of causation is derived. Hume would put the point in terms of the Way of Ideas as follows: we must determine from what impression our idea of causation is copied. However, Hume believed he had discovered that there is nothing in our sensory experience corresponding to our ordinary notion of the causal relation. In an inversion of the empiricist method attributed to Reid above, Hume believed that causes necessitate their effects, then he followed this commitment by arguing that we lack sensory awareness of this necessitation. We see the first billiard ball hit the second. We see the second move. We do not see the movement of the first assure, or necessitate, the movement of the second. So Hume concludes that causation must be something different from what we take it to be ordinarily. 