Abstract

Hume's regularity theory of causation was partly motivated by a criticism of Descartes' causal account of collisions. According to Descartes, bodies are things with extension, and since having extension does not entail any ability to cause changes of motion in other bodies, such changes must be explained by attributing a ‘causal power’ to bodies, logically independent of their extension. Hume's point is that we can't observe any such causal power and we should not use ideas about such unobserved qualities of bodies. Given his form of empiricism, the regularity theory is the only choice; causation is no more than constant correlation. However, there is a third option beside attributing a metaphysical ‘causal power’ and mere regularity; if we follow Newton and say that bodies are characterised and individuated by their mass, not their extension, we can give another analysis of causal interaction between bodies. It is by having mass a body can cause changes in the motion of other bodies. Thus, using classical mechanics we can give an alternative to Hume's regularity theory of causation in which the necessary connection between cause and effect is understood as a conceptual connection between certain descriptions of cause and effect. It does not satisfy Hume's strictures on concept formation, but no additional metaphysics is necessary. In a sense it is an intermediate position between Humean regularity and an account in terms of metaphysical necessity.