Abstract:
There is a growing consensus that causation can come in degrees. For instance, if two companies both emit effluents into a river, the degree to which they should be held responsible for the resulting damage depends on the degree to which they causally contributed to it. In general, if an event e has two contributing causes, c1 and c2, the causal contribution of c1 to the occurrence of e may be greater than the causal contribution of c2.
In this paper I investigate what a theory of degrees of causation should look like. Most theories currently on the market are quantitative and measure closeness to necessity: they assign a concrete numerical value to each cause in a given causal structure, and assume that this values depends on how close the cause comes to providing a necessary condition for the effect. However, I argue that a theory of graded causation should be comparative and measure closeness to sufficiency: it should only rank causes according to their relative contribution to a given effect, and assume that this ranking depends on how close the cause comes to providing a sufficient condition for the effect. My argument is based partly on the relationship between degrees of causation and degrees of responsibility mentioned above, and partly on more general considerations about the role of degrees of causation in scientific and everyday contexts.