0. Herewith, some interpretative notes on Curt Ducasse, "On the Nature and Observability of the Causal Relation," in Causation, eds. Sosa and Tooley, Oxford 1993, pp. 125-136.
1. Assuming that causality is a relation (not entirely obvious!), the question arises as to what sorts of entity can serve as its relata. Following Schopenhauer, whom he cites, Curt Ducasse holds that in strict propriety only events can be causes and effects. An event is either a change or an absence of a change. Thus a tree's losing its leaves is an event, but a tree is not. In strict propriety, it makes no sense to say that Bill was killed by a mountain lion. One has to say something like: Bill was killed by the attack of a mountain lion. In the attack the lion is the agent as Bill is the patient, but the latter is no more the effect than the former is the cause. The cause is the lion's attack, the effect is Bill's death. Some theorists distinguish between agent-causation and event-causation, but for Ducasse, there is no such thing as agent-causation: causation just is event-causation.
2. For Ducasse, events are not punctual but processual. No change or 'unchange' occurs at a time, but only over an interval of time, or at a point (or other cut of space), but only through a space between cuts. Thus causes and effects are processes.
3. Let C and K be particular changes, change-tokens rather than -types. If the occurrence of C suffices for the occurrence of K, then C causes K. Thus for Ducasse the task of defining causation is the same as that of defining this non-logical sufficiency. C causes K if:
(A) The change C occurred during a time and through a space terminating at the instant I at the surface S. (B) The change K occurred during a time and through a space beginning at the instant I at the surface S. (C) No change other than C occurred during the time and through the space of C, and no change other than K during the time and and through the space of K. (127)
In brief, C causes K iff C alone occurs in the immediate environment of K immediately before.
4. Example. A rock collides with a window, breaking it. This is a case of causation if anything is. The cause is not the rock, but the rock's colliding with the window; the effect is not the window, but the window's breaking. The change in the rock's position is immediately followed by a change in the window's integrity, and the change in the rock's position is the only change in the immediate environment of the window immediately before the change in the window's integrity.
Think of it this way. (Cf. Sosa and Tooley's introduction, p. 18.) The immediate environment of the window is a continuous spatiotemporal volume. Slice through this volume on a plane perpendicular to the time-axis. Make the cut at the moment of collision. You now have two spatiotemporally contiguous sub-volumes. The processes, states, and events in the earlier sub-volume constitute the cause C, while the items in the later sub-volume constitute the effect K. C's causing K is nothing other than K's contiguously following C.
5. This is close to David Hume's theory, but without constant conjunction. There is only spatiotemporal contiguity and temporal precedence. Now is the causal relation observable? Hume looked hard at his billiard balls but discerned no causing, no producing, no necessitating when the cue ball slammed into the object ball. He saw "distinct existences" but no causal connection. On Ducasse's view, however, Hume made the mistake of assuming that the connection, to be anything, must be a third entity, a third "distinct existence" separate from the cause and the effect. Ducasse: "Hume's view that no connection between a cause and its effect is objectively observable would be correct only under the assumption that a 'connection' is an entity of the same sort as the terms themselves between which it holds, that is, for Hume and his followers, a sense impression." (131)
Ducasse goes on to point out that even if there were a distinct empirically discernible link between cause and effect, this would not solve the problem but raise another: what connects this connector to what it connects? For Ducasse, the causal connection is not a sensory impression but a relation, the relation analyzed above. Moreover, it is an observable relation. "We observe it whenever we perceive that a certain change is the only one to have taken place immediately before, in the immediate environment of another." (132) Thus when I see a lightning bolt hit a tree and the tree burst into flame, and I see nothing else then and there, what I am seeing is the causal relation.
Ducasse's view seems very close to this: If you can perceive change, you can perceive causation. To put it more precisely: If, in a circumscribed environment, you perceive one change contiguously following another, then you are perceiving causation. One change contiguously following another in an environment is itself a change. So it seems fair to say that, for Ducasse, the perception of causation is just the perception of change. Ducasse himself, in footnote 11, points out
. . . an essential connection between the two notions of Change and of Causation. For, taking any given change process, by specifying a space-time cut of it, one splits it into a cause and an effect; and, on the other hand, taking any given cause and its effect, by abstracting from the particular space-time cut in terms of which as common limit the cause process is distinguished from the effect process, one obtains a process describable as one change. This calls to mind Kant's very inadequately argued contention in the Second Analogy, that (objective) change involves the category of causation. (129)
6. Ducasse's theory raises many questions. Here is one. Ducasse's theory seems to imply that every case of change is a case of causation. But consider a moving shadow cast by a moving car. Since the shadow is moving, it is changing in respect of position as it travels from A to B. Now we just heard Ducasse say that "any given change process" can be split into a cause and an effect. So make a cut in the spatiotemporal volume mid-way between A and B, and call the earlier process the cause and the later the effect. But it is clear that the earlier process is not the cause of the later process. A moving shadow is not a causal process but a pseudo-process. So here it seems there is a case where there is more to causation than change. The shadow's being in a given position at a given time is not the cause of its being in a different position at a later time.