Chapter 2: Kim’s causal exclusion argument against non-reductivism
2.5 A hidden premise in the exclusion argument
2.5.4 The transference of conserved quantities and the problem of relevance
What was said above provides dual motivation for accepting the concept of causation Kim preferred in his later writings (2005, 2007), reacting to early criticism from Menzies (2003) and others, a version of process theories, the so-called conserved quantity theory that falls into the category of production theories. First, this theory stands a good chance of explaining our intuitions concerning both early and late pre-emption scenarios as the concept involves spatiotemporal contiguity between causes and effects. Second, it can easily agree with the diagnosis concerning the status of absence causal talk. Absences are not causes, but by talking about them we can deliver genuine causal information to others.
A common feature of theories of causation that build on the idea of a physical transference between causes and effects is that they don’t aim for a reconstruction of causal talk. Their supporters, walking the revisionist path of the naturalist, base their notion of a cause on some interpretation of contemporary physics. The best interpretation of the later Kim’s idea concerning causation is that in his conviction some physical transference view of causation provides the actual-world grounding of a more abstract production view of causation. In what follows, I will summarize the gist of the conserved quantity account that is still the most popular process interpretation of causation to be able to show that, when it comes to causal relevance, it suffers from the same kind of problem regularity accounts suffer from. After that, I will allude to some viable solutions for pre-emption scenarios in later versions of the counterfactual theory of causation to show that much of Kim’s complaints against counterfactual theories lost motivation.
garden”. But even if it is referential it is still true that there is no space-time contiguity or relevant physical transfer between this event and the “withering of the flower”. A “nap in the back garden” has no potential power to make flowers to wither.
I will start by summarizing the essence of Dowe’s physical theory of causation. Dowe (2000) defines causal processes and causal interactions in terms of conserved quantities. Conserved quantities are physical quantities under the governance of a conservation law of physics. Linear momentum or charge are straightforward examples. In Dowe’s conceptualization a physical process is a world-line of an object possessing a non-zero quantity that is conserved. The concept of a world-line originates in relativity theory. It is the path an object traces in spacetime (in 4 dimensions). It is a sequence of events in spacetime corresponding to the history of the object. A causal interaction takes place when the world- lines of two objects cross each other and an exchange of conserved quantity takes place between them (e.g. of linear momentum). This account was set out to capture objective features of causal interactions in our world as they happen according to our best physical theories. It is not interested in causal mechanisms in faraway possible worlds nor in pure conceptual analyses.
Let’s introduce a counterexample that is widely used in the physical causation literature. Imagine a man playing a game of billiards. He hits the cue ball with the cue and the cue ball projects a red ball into one of the corner pockets on the table. Earlier the player has chalked the end of the cue with chalk. When making the strike some of the chalk sticks to the cue ball. Some of the same chalk spot gets transferred to the surface of the red ball when the cue ball bumps into it. At the end the red ball lands in the corner pocket. The question is, what caused the red ball to land in that corner pocket? Intuitively the push by the cue ball that originated from the cue. A more scientific explanation would refer to the linear momentum of the cue ball. Can the conserved quantity theory deliver these results?
Both parts of the chalk that came from the cue and the linear momentum are getting transferred to the red ball in the interaction between the red ball and the cue ball. There are
two different conserved quantities travelling through the billiard table. According to the conserved quantity theory a causal interaction is an exchange of conserved quantities. Two exchanges took place, but the theory provides no resources to decide which is relevant for the outcome, they are indistinguishable in its terms. Woodward explains this nicely:
“the feature that makes a process causal (transmission of some conserved quantity or other) tells us nothing about which features of the process are causally or
explanatory relevant to the outcome we want to explain. For example, a moving
billiard ball will transmit many conserved quantities (linear momentum, angular momentum, charge, etc.), and many of these may be exchanged during a collision with another ball. We still face the problem of singling out the linear momentum of the balls, rather than these other conserved quantities, as the property that is causally relevant…” (Woodward 2003:357, my italics)
What makes the situation even more difficult for believers of the conserved quantity theory is that there are cases of higher-level causation where there appears to be no conservation law governing the properties involved. Imagine that my anger makes my friend sad. On the face of it, the conserved quantity theory makes my anger causally impotent. One can always revert to the idea that there has to be an underlying physical process at least at the microphysical level realizing my anger that involves some conserved quantity, but that does not help to decide question of causal relevance.
The problem identified here is similar to the problem regularity accounts faced concerning relevance. A comparison with what the counterfactual analyses can deliver in such simple cases as the one involving billiard balls speaks for itself. The sentence “had the chalk not transferred to the surface of the red ball the ball would have ended up in the same corner
pocket”57 is plausibly true, therefore the chalk was not relevant to the outcome. Whereas if
the sentence “had the cue ball had just slightly different linear momentum it wouldn’t have ended up in the corner pocket” is true it clearly shows the relevance of linear momentum for the outcome. So, the counterfactual account is still superior in terms of relevance.