Philosophical and Scientific Perspectives on Downward Causation

Michele Paolini Paoletti, Francesco Orilia, Michele Paolini Paoletti, Francesco Orilia

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781317271437
• Edition: 1
• Topic: Filosofía
• Subtopic: Historia y teoría filosóficas

Downward causation plays a fundamental role in many theories of metaphysics and philosophy of mind. It is strictly connected with many topics in philosophy, including but not limited to: emergence, mental causation, the nature of causation, the nature of causal powers and dispositions, laws of nature, and the possibility of ontological and epistemic reductions. Philosophical and Scientific Perspectives on Downward Causation brings together experts from different fields—including William Bechtel, Stewart Clark and Tom Lancaster, Carl Gillett, John Heil, Robin F. Hendry, Max Kistler, Stephen Mumford and Rani Lill Anjum —who delve into classic and unexplored lines of philosophical inquiry related to downward causation. It critically assesses the possibility of downward causation given different ontological assumptions and explores the connection between downward causation and the metaphysics of causation and dispositions. Finally, it presents different cases of downward causation in empirical fields such as physics, chemistry, biology and the neurosciences. This volume is both a useful introduction and a collection of original contributions on this fascinating and hotly debated philosophical topic.

1
Downward Causation

An Opinionated Introduction

Michele Paolini Paoletti and Francesco Orilia

Downward causation is a widespread and problematic phenomenon. It is typically defined as the causation of lower-level effects by higher-level entities. Downward causation is widespread, as there are many examples of it across different sciences: a cell constrains what happens to its own constituents; a body regulates its own processes; two atoms, when they are appropriately related, make it the case that their own electrons are distributed in certain ways. However, downward causation is also problematic. Roughly, it seems to be at odds with specific scientific and/or epistemological desiderata: first and foremost, that everything can be reduced (one day or another) to the fundamental, micro-physical constituents and goings-on of the universe, so as to provide a unified explanation of everything and a unification of all the sciences “from the bottom”. Indeed, downward causation (if it is an irreducible phenomenon) introduces special causings not only at the higher levels, but also at the lower ones: if, in principle, we cannot fully understand what happens to the electrons without paying attention to the atoms (at the higher level), and we cannot fully understand what happens to the atoms by only paying attention to the electrons (at the lower level), there is no fully lower-level explanation for both higher-level and lower-level goings-on.

In this introduction, we shall try to describe the prospects for downward causation in metaphysics and the philosophy of science. After having delved into the connections between downward causation, emergence and levels (section 1), we shall discuss the irreducibility of downward causation (section 2). We shall then briefly consider how specific metaphysical and epistemological assumptions bear on our understanding of downward causation and of its possibility (section 3) and describe some views according to which downward causation is actually non-causal (or it is a somehow special causal relation) (section 4). We shall also mention some problems for the connection between downward causation and mental causation (section 5) and some scientific examples of downward causation (section 6). Finally, we shall summarize the contents of the contributions in this book (section 7).

1. Downward Causation, Emergence and Levels

Downward causation is commonly linked to emergence: an entity acting as a downward cause is an emergent entity, and vice versa.

There are many different and competing views of emergence. For some authors, emergence is a merely epistemic phenomenon: something emerges from some other thing, roughly, if and only if the former is not predictable from the latter. However, a prominent view of emergence takes it to be something real in the universe. For it seems that there must be something in the universe that makes it the case that an emergent phenomenon (even the existence of an emergent entity) is not predictable from other phenomena—where the unpredictability is not merely due to the epistemic limits of human beings. Thus, emergence is a real phenomenon. What sort of phenomenon? It is possible to distinguish here between two degrees of emergence. Following Bedau (1997), there is weak emergence whenever one needs to adopt special methods in order to predict something from some other things. Such special methods are motivated by certain objective features of the entities involved. For example: we should need to take into consideration certain special relations between entities (and certain special laws involving those relations) in order to predict the behaviour of a system constituted by those entities. On the contrary, there is strong emergence whenever a certain higher-level entity possesses (or confers) certain irreducible causal powers, i.e., whenever it is causally responsible for certain happenings that cannot be due (only) to the lower-level entities on which the former is taken to depend.¹ For example: certain mental properties could confer special and irreducible causal powers, besides the ones conferred by other properties on which they depend (e.g., neural properties).

Insofar as downward causation is taken to be an irreducible phenomenon, it can be connected only with strong emergence. For weakly emergent phenomena can be fully explained in lower-level terms, even if one needs to adopt special methods. In addition, Kim (1999) has tried to demonstrate that strongly emergent entities must confer (or possess) downward causal powers. Indeed, the only way for a strongly emergent entity to cause a certain higher-level effect is by causing the lower-level phenomena on which the latter depends. For example: in order for pain to cause a specific volition, it must cause the instantiation of the neural properties on which that volition depends.

Kim’s arguments can be questioned. Moreover, if strong emergence and downward causation are essentially connected, they seemingly turn out to be interdefinable. A strongly emergent entity is one that confers/has downward causal powers, i.e., powers to be exercised with respect to the lower-level entities. Yet, a downward causal power is one that belongs to an entity of a higher, strongly emergent level and that can cause something at the lower levels. Downward causation is invoked to define emergence and emergence (“emergent levels”) is invoked to define downward causation. Such definitions make both notions unanalyzable, as we need downward causation in order to analyze emergence and emergence in order to analyze downward causation.

If this is to be avoided, levels must be defined without invoking emergence. At a first glance, one could invoke constitution relations:² if something constitutes some other thing directly (i.e., without constituting some further thing that constitutes the latter), then the former belongs to a certain level l and the latter belongs to a proximate higher-level l +1. Some questions are in order: since there are many ways (from an epistemic standpoint) to carve nature at its joints, what makes it the case that some of them are more “legitimate” than others? Moreover, if we accept the Principle of Unrestricted Composition, all sets of entities turn out to constitute further entities.³ Thus, what makes it the case that some constituted entities are more “relevant” than others? Do all the “relevant” constituted entities have downward causal powers? What are the levels of constitution in the universe, both within sciences and across sciences? Finally, the ontology of levels itself has been recently criticized (Heil 2012).

Such problems are still open and there is no easy solution to them. On the contrary, it seems that, for many years, the connection between downward causation, emergence and levels was taken for granted as an unproblematic phenomenon and levels were mostly understood in an intuitive way, by simply paying attention to constitution and the distinctions between sciences.

2. The Irreducibility of Downward Causation

Kim (1999) presents an argument against the irreducibility and novelty of downward causation that will be examined in some of the contributions. It rests on the idea that an emergent property and its lower-level, emergence base are both nomologically sufficient (i.e., sufficient given the actual laws of nature) for the production of the lower-level effect. In turn, this idea is motivated in two different ways. In Kim (1999), nomological sufficiency is taken to be a transitive relation: if a lower-level emergence base is nomo-logically sufficient for a higher-level emergent property (given that the latter emerges from the former according to certain laws of nature) and the higher-level emergent property is in turn nomologically sufficient for the lower-level effect (given that causation implies nomological sufficiency), then the emergence base is nomologically sufficient for the lower-level effect too. In other places (e.g., Kim 2005), the emergence base is nomologically sufficient for the production of the lower-level effect if they are both (micro-)physical and the principle of the causal closure of the (micro-)physical realm is true. This principle asserts that every (micro-)physical effect has a wholly sufficient (micro-)physical cause, which can be identified here with the emergence base. At any rate, in both cases, downward causation turns out to be “redundant”: the lower-level entities are causally sufficient for all the lower-level effects.

There are three ways to comply with Kim’s arguments: (i) accepting them and holding that downward causation is actually reducible; (ii) rejecting their assumptions (first and foremost, the principle of the causal closure of the (micro-)physical); (iii) accepting their assumptions and finding a different role for downward causation.

If we choose (i), downward causation turns out to be a rather uninteresting phenomenon. Yet, if we choose (ii), we need to demonstrate that there are causal gaps at the (micro-)physical level of the universe: gaps which can only be filled by non-(micro-)physical entities. More radically, we also need to ask: why should we accept the principle of the causal closure of the (micro-)physical realm? Brian McLaughlin (1992) and David Papineau (2000) hold that, if there are non-(micro-)physical causes operating at the (micro-)physical level, such causes must introduce special physical forces and/or violate the principles of the conservation of energy and momentum. Thus, it is reasonable to hold that there are only (micro-)physical causes of (micro-)physical effects. Among others, Sophie C. Gibb (2010) has tried to demonstrate that this is not necessarily the case. Scott Sturgeon (2003) has argued that quantum physics is actually compatible with there being causal gaps at the (micro-)physical level. But even if this is so, the next question is: can all cases of downward causation be accounted for by simply acknowledging such (micro-)physical causal gaps?⁴ Eventually, those who adopt (iii) either claim that downward causation actually is a non-causal relation (see section 4) or that downward causation has special sorts of relata as causes and/or effects. For example: the causal closure principle is taken to concern (micro-)physical events, both qua causes and qua effects. Yet, in irreducible cases of downward causation, there could be different sorts of causes and/or effects at work. For example: agents qua substances could be responsible for downward, mental causation; facts instead of events could be the relevant lower-level effects (Lowe 2000). Two problems are left open. First, these assumptions about special causes and/or effects should be accommodated within a general metaphysical theory of causation. Inter alia, such a theory should try to settle whether there are many different forms of causation (e.g., event causation, fact causation, etc.). Secondly, since the causal closure principle can be rephrased so as to encompass these forms of causation and the special entities that they involve, it must be shown that the relevant reformulations of the principle are less justified than the original formulation in terms of events.

In addition to Kim’s arguments, there are also some empirical concerns about the irreducibility of downward causation, due to the idea that downward causation can be replaced by special, lower-level phenomena. For example: mechanisms are taken to be lower-level structures of entities and activities that are meant to explain certain peculiar effects in biology and the neurosciences—phenomena that one might have otherwise interpreted as due to downward causation.⁵ More generally, reductionists could grant that certain lower-level entities cause specific lower-level effects only if they stand in peculiar arrangements. Such arrangements could then replace higher-level causes. However, the reductions provided by such strategies are successful only if the lower-level “surrogates” of higher-level causes depend in no way on the higher level. Otherwise, the reductionist project would fail. If we still needed the higher-level entities in order to single out their relevant “surrogates” (e.g., if we still needed mental properties in order to single out their relevant neural “surrogates”), there would be at least a conceptual problem for the reductionist project: the higher level would not actually turn out to be redundant.⁶

3. Downward Causation and the Metaphysics and Epistemology of Causation

We have seen that one strategy for dealing with the problems of irreducible downward causation consists in changing its relata. For example, it has been recently suggested that one should adopt a process ontology in order to allow for both emergence and downward causation. Such a process ontology would also be more compatible with the scientific picture of the fundamental level of the universe.⁷ Yet, a more radical question about causation emerges: what is it for something to cause some other thing?

According to some philosophers, physical causation is the transmission of some conserved physical quantity, such as energy.⁸ If this is the only form of causation, irreducible downward causation turns out to be very problematic: in order for it to be irreducible, it must introduce some novel form of energy or change the amount of energy at the lower level. However, we are forced to admit neither that physical causation is the only form of causation nor that any physical effect is brought about by changing some conserved quantity such as energy. It is also worth asking what one means by “physical effect”. On the one hand, a physical effect could be anything involving some physical entity/-ies. On the other hand, it could be the instantiation of a physical property/relation (i.e., of a property/relation typically studied by physicists) by some physical entity/-ies.⁹ On the latter view of physical effects, it might well be the case tha...