Chapter 2: Kim’s causal exclusion argument against non-reductivism
2.4 Exclusion and no overdetermination
2.4.4 Genuine inter-level overdetermination and different notions of causation
Even though mental and physical causes are linked up by supervenience, if mental causes are truly autonomous both causes should be sufficient for the physical effect in themselves. Remember two things. First, for Kim (see especially in his 2007) causation is some kind of production that can be spelled out, for example, in terms of energy transfer. Second, that in his view mental properties or higher-level properties in general, in case they are not epiphenomenal, but still irreducible have to “bring with them new causal powers, powers that no underlying physical-biological properties can deliver” (Kim 1993:350). Here he relies on Alexander’s dictum, according to which something to exist has to have autonomous causal powers. This means that in inter-level overdetermination scenarios both mental and physical token causes have to have autonomous contributions to an effect.
On the one hand, this contribution results in what we called the threshold effect and on the other hand, as together the contributions produce some excess over and above the former, a cumulated effect. The latter point follows straightforwardly if causation is understood as some kind of energy transfer. If causation is energy transfer, then overdetermining causes must transfer more than the energy one of those causes would have transferred alone. Under this interpretation of causation this result is a necessary consequence of how causation is understood and what overdetermination by separate causes means.
However, I don’t think that the argument requires us to rely on physical causation, be it energy transfer or any other version of physical causation. The result follows even if one relies on a counterfactual theory of causation. It is interesting that an important critic of Kim, Loewer (2007) agrees with Kim in finding overdetermination problematic if causation requires
something like the transfer of energy, but also thinks that if causation is counterfactual dependence the problem evaporates.
It might be that counterfactual causation allows more space for getting rid of the problem of overdetermination, what I am sure about is that it does not help if the overdeterminers are separate existences. There is robust empirical evidence that redundant causes, independently of the interpretation we choose, together bring about an excess effect over and above the threshold effect that shows itself in the same space-time region where the threshold effect takes place that any of the redundant causes would have caused alone. The excess effect grows or changes with the number of redundant causes. So, it seems that it does not matter whether we prefer the counterfactual analyses or a physical theory of causation, empirically speaking the cumulated effect is there in available examples even if causation is not reducible to energy transfer.
Bunzl (1979) expresses the same basic idea from a conceptual point of view. He thinks that overdeterminer causes and their effects should be understood as joint causes of an effect that is underdescribed. A description of the same effect in terms of fine grained, modally fragile events reveals that each seemingly redundant cause of this effect is as necessary for it as are other causes that we usually relegate to the set of background conditions. The pouring of the two glasses of water into the bowl are both necessary for the fine-grained outcome, the kind of bowl overflow that takes place, as much as the ambient temperature in the room is.
Schaffer (2003) has a reply to this argument, which he borrows from David Lewis. Going fragile concerning events should be rejected as it conjures up spurious causes. Any tiny difference in the past (every event in the back light-cone) of an effect event can contribute to differences in its manner and time of occurrence, but causal discourse seems to dismiss those
contributions. I agree with this observation, I think it is fair to say that the threshold effect, the coarse-grained effect event is not caused by those spurious causes and as McDermott (1995) tried to show on experimental grounds, the majority of naive students do share this judgement. I agree with that, if the task for a philosophical account of causation is pure conceptual analysis, then it should respect those intuitions. But I think the solution to the issue at hand lies elsewhere. It has more to do with the perspective from which we ask our questions concerning causes and effects.
We can ask at least two kinds of different, but equally objective questions concerning all causal situations. First, what contributed to this or that particular outcome, an event under such and such a description. This is what the idea of a threshold effect captures. Second, we can also ask what difference is made to the outcome by certain manipulations we make on its potential cause events. So, we can approach the causal relation from the front end as well. We can ask what difference is made to a body by two bullets instead of one.
We only lose sight of certain objective dependency relations redundant causes are involved in in the world as relevant factors when we attend to a particular coarse-grained threshold effect and approach the causal relation from the back end. Presenting the same causal scenario from the second perspective shows that what counts as a redundant, non- difference-maker cause from the first perspective counts as a difference-maker for something the first perspective dismisses. In all the overdetermination scenarios we have discussed, the extra difference is made to some disregarded aspect of the same effect event. What I would like to highlight here is that the difference-making power of redundant causes doesn’t dissipate into nothingness just because they are irrelevant for an outcome under a particular description that is interesting for us for some arbitrary purpose. It just brings about something that is unimportant from that particular perspective.
Even if causes are conceptualized in counterfactual terms, we would say that a cause is a cause whenever it makes at least difference, not just when it makes a difference to something we highlight as important to us. Finer-grained descriptions of the world help us to discover objective causal dependencies that are invisible from a coarse-grained perspective, and as my examples have shown that is of high importance when it comes to investigations into the origins of certain effects, like deaths.
188.8.131.52 Overdetermination by negative causes
One might still argue that my argument piggybacks on a simple feature of the examples. They are examples of positive causation involving contiguity and some form of energy transfer. But difference-making theories allow for negative causation as well: cases where the absence of something makes a difference. Can’t we construct cases where absences are causing something without having an excess effect? Absences don’t transfer anything to their effects, so this sounds like a fair starting point.
Let’s investigate a well-known scenario where the omission of an activity causes an outcome. A gardener fails to water flower, and it dies (McGrath 2005). Let’s turn it into a case of overdetermination. Imagine that there is a couple who own the flower. Both of them are watering the flower regularly, giving a glass of water every day. The flower requires a lot of water, so one glass wouldn’t be enough to keep it alive. Imagine further that one day both members of the couple forget to water the flower and it dies. This is a case of overdetermination as the absence of both acts of watering is more than what is required for the flower to die. The absence of one would have been enough. Absences are not connected to their effects by physical transfer. The interesting question for the present discussion is, can they make a difference to the way the flower dies?
They can. Compare and contrast a scenario where only one of them waters the flower with the one where neither of them. The flower dies in both cases, but in a different way. In the overdetermined case it has less water in its cells, so the so-called turgor pressure of the cells is lower and therefore plausibly it looks way more withered than in the other case.
Note, that this has nothing to do with the kind of spurious causation Schaffer (2003) talks about. This is not about small irrelevant traces of faraway events accumulated in irrelevant parts of the respective effect event. Despite the fact that there is no transfer of energy between the gardener and the flower, fine-grainers like Bunzl (1979) would be forced to accept that the specific state the dead flower arrived at because of the absence of water is partially caused by what each of the owners is doing instead of watering, such as lying on the beach in a different country. But I wasn’t attending to such minuscule traces when arguing for the necessity of excess cumulated effects from overdeterminers. I compared the differences that overdeterminer events make together and alone to the outcome directly. So, there is a strong case for the importance of such cumulated effects even if causation is analysed in terms of counterfactuals and negative causation is accepted as genuine causation.