ABSTRACT
Medieval philosophical theories of causation are in many ways very different from modern ones. An understanding of some of these differences may help to make Scotus’s account of God’s existence intelligible, and perhaps even plausible. And it will help too with understanding Scotus’s theology of the intra-Trinitarian relations of the divine persons. Medieval views of causation generally involve an analysis in terms of substances causing effects (in other substances). The causes here are substances with (active) powers to do things, and what they do is affect things with (passive) potencies or capacities to be affected in the relevant way: paradigmatically, x brings it about that y is φ, where x and y are two different substances, and where x has the relevant power (to make things φ), and y the relevant capacity (to be made φ). Modern views of causation tend to suppose that causal relations obtain between events. Talk of causation in this way has a great ontological advantage: it renders superfluous any talk of substances and their powers. This is an advantage of economy. But the advantage comes at a price (and so is, in a different way, uneconomical): namely, a loss of explanatory force. For in event–event analyses, causation is usually reduced to one or other of two sorts of relation: constant conjunction or counterfactual dependence. On constant-conjunction theories, all there is to causation is one event’s regularly or constantly following another. Counterfactual-dependence theories specify the relation a little more closely: an event x counterfactually depends on an event y distinct from x, if both, x and y obtain, and if y did not obtain, x would not obtain. Neither of these accounts is very satisfactory. They both deny what seems to be central in our intuitive notion of causation, namely that there is some sort of connection between cause and effect. A definition of causation that is faithful to our intuitions on the matter would have to include the fact that a cause seems to make some genuine contribution to the effect: something that the cause is or does is responsible for the effect; the effect somehow derives from the cause.
