An Identity Theory of Causality

An Identity Theory of Causation

Let causal dualism be the doctrine that cause and effect are separate things, one following the other in time: first the cause, then the effect.[1] There is no overlap between the two; they are quite distinct events. The short circuit caused the fire: one event (or state of affairs) caused another event (or state of affairs), period. The billiard ball striking another billiard ball made it move away–the striking and the moving being different occurrences. This is opposed to the view that talk of cause and effect is really talk of the same thing: we have a dualism of descriptions not a dualism of objects. Logically, the case is like mind and body: do we have a dualism of objects or a dualism of descriptions (senses, perspectives)? Granted we have causal interactions, but do these consist of a cause-effect pair, discrete and asymmetric, correlated but not identical?

One billiard ball strikes another billiard ball and that ball moves away—the former causes the latter. These seem like distinct existences. But consider: the second ball causes the first ball to slow down, perhaps stop in its tracks; it impedes the motion of that ball, which would have gone on in a straight line if not obstructed. We can imagine someone putting the impeding ball there on purpose so as to secure the result in question—to get that effect. One ball causes the other to move away (acceleration), but that ball causes the other to slow down (retardation). The causation was reciprocal. How many things happened? Can’t we say there was just one, a collision of billiard balls? There are two ways of describing it, but only one thing was done—sending one ball into another. The moving away and the stopping are aspects of the same event. What we call the effect (moving) actually caused a change in the cause (stopping). The effect had an effect on the cause. The stopping and the moving were aspects of the same basic event—the collision. Collisions affect both parties—the impact is mutual. There was an event of collision and it can be described as causing a ball to move or causing a ball to slow down. Something happened between the two balls, and that is the fundamental causal reality. That something was highly localized: momentary contact between parts of the surfaces of the two balls. The rest of the balls is strictly irrelevant to the causal nexus. There was a localized touching event and that is what led to the two effects of moving away and slowing down. The touching event was the core of the causal interaction; it can be described in cause language or effect language—a touched b or b touched a. The fact is that a and b touched each other. This symmetrical touching is the causal reality. It isn’t that the cause is a separate thing from the effect—as if the moving ball were merely an effect and not itself a cause. The touching is both cause and effect; it is both what caused the moving and what caused the stopping. It isn’t that causes are active and effects passive; both are active and passive. Every causing is a case of being affected and every being affected is a case of causing. It isn’t that some things are intrinsically causes and some things are intrinsically effects, and never the twain shall meet; all causation is both. One man’s cause is another man’s effect, and one man’s effect is another man’s cause. There could be a game of billiards in which the sole purpose is to block the other player’s balls: you score points when you force your opponent to make contact with your balls, while he tries to sink his balls into the pocket without touching your balls. The effect you are seeking is his ball making contact with yours. What we call the effect is relative to the point of the game. As far as nature is concerned, everything is both a cause and an effect; you are talking about the same thing from different points of view. Objectively, there are just symmetrical collisions—mutual touching. A cause is a touching and an effect is a touching—the same touching. Hence, the identity theory.

Suppose you press your finger into a piece of soft rubber. You cause it to deform into a dent; the dent, we say, was an effect of your finger pressure. But the rubber also put up some resistance to your pressure and caused your flesh to shift a bit; the shift was an effect of the rubber’s resistance. The effect caused an effect on the cause. Yet there was only one thing going on—finger and rubber being pressed together. You pressed and it pressed. The cause was the effect: the finger pressing down was the rubber pressing back. The purpose of the act could have been to exercise the finger, in which case we would have described this as the effect and the rubber the cause; while if we wanted to make a dent in the rubber, we would have said that the finger was the cause. There is causing and effecting, and these are the same. There are causal nexuses, and that’s all. Causal relations are not one damn thing after another, causes asymmetrically preceding effects; they are simultaneous reciprocal interactions, symmetrical links. When Newton said that for every action there is an equal and opposite reaction, he was expressing much the same point: causation always cuts both ways and is essentially an action-reaction nexus. It is better to speak of causality not of cause-effect relations. Effects arecauses, as the mind is the body (for an identity theorist). Our customary talk of cause and effect is pragmatically shaped; metaphysically, there is no such sharp division. Does the Sun cause plants to grow via photosynthesis? You can talk this way, but remember that plants cause the Sun’s rays to be absorbed and used in photosynthesis (they affect the Sun’s light). These are part and parcel of the same interaction: photon absorption. Causal dualism imposes a spurious dichotomy on causality, forcing causes and effects into exclusive categories; in reality, causality consists of multiple causal nexuses that can be variously described. Thus, I prefer to speak of causal monism—a causal identity theory.

If we switch our attention to objects (substances) and causality, we get a clearer picture of the metaphysics of causation. The ontology of events in discussions of causality is only part of the causal picture. For it is clear that there are no intrinsically cause objects and intrinsically effect objects; there are just interacting objects. The Sun warms the Earth and the Earth absorbs the Sun’s energy. Objects interact with their environment all the time, acting and being acted on. If you cut down a tree, it blunts your blade; the saw is both a cause object and an effect object. There is no sense in trying to classify it as one or the other. An identity theory of object causation is the indicated position. Neutral monism about causation is the way to go. The world is not inherently divided into causes and effects; it isn’t the totality of these. The causal cement of the universe is not a compound of causes and effects (like H2O), i.e., distinct ontological categories; it is a totality of causal nexuses. We carve these up in various ways, using the concepts of cause and effect; but it is a mistake to project this division onto reality, as if we had hold of distinct metaphysical natural kinds. What we call cause and effect is merely the appearance of causal reality.[2]

[1] I think causal dualism is endemic to philosophy, especially analytical philosophy, and perhaps to human thought generally. It may help the reader to keep in mind Davidson’s treatment of causal statements, which crystalizes the doctrine in question; also, the positivist way of thinking about causality, biased as it is towards epistemological considerations (how we experience causality). I am trying to peer into the deep metaphysics of the subject, not the logical form of causal statements or how we experience and know causal truths. I want to grasp the ding an sich.

[2] This paper was difficult to write. It required me to think hard about matters that are difficult to grasp and even more difficult to express; I felt always on the brink of saying something strictly false, but essentially true. I won’t be surprised if my readers react with bemusement. It really isn’t easy to see into a reality that differs from our ordinary ways of talking and thinking. Causality has always been a very tricky subject. As Hume realized, it taxes our intellectual resources. I don’t think I’ve ever read anything on the subject I found intellectually satisfying. Most philosophers wisely steer clear of the subject. It ought to be easier.