Downward causation

Michel Morange I didn t get the sense of downward causation. What is really downward or upward causation ... 

John Dupre Or you d explain human behaviour in terms of the interactions of brain cells. The opposite, downward causation, would be, for example, to say that the behaviour of a person causes their brain cells to move in a certain way. Lisa s example today, I take to be, as she just summarised it, precisely a claim to downward causation. That is to say that the social phenomena actually act causally on the individual, and, of course, to deny what is a very common thesis in the philosophy of social phenomena, which is methodological individualism, which says, and many people, social scientists and philosophers have said - you have to be able to explain social phenomena by looking at the behaviour of individuals. And that s the reductionist view as opposed to the downward causation view, which is an anti-reductionist view. And I think that s certainly one of the standard ways philosophers have understood the debate. 

Armando Aranda So, sorry, is it because in relation to what Dupre has said that I presume that downward causation can be based on something stronger and deeper than correlations ... 

Downward causation is the influence the relatedness of the parts of a system has on the behaviour of the parts... it is not the influence of a macro-property itself, but of that which gives rise to the macro-property, viz., the new relatedness of the parts. 

Of course molecular-science examples are not the only ones to show the effect of downward causation. This is so for all aspects of emergence. Consider the progression of hierarchic levels that go from the individuals to the family to the tribe to the nation it is clear that once the individuals have a family, the rules of the family affect and change the properties of the individuals, and so on. 

Schroder, J. (1998). Emergence non-deducibility or downward causation Phil. Q., 48, 434-52. 

Would anyone have doubted the usual direction of dependence of levels by considering a chemical reaction For example when compound A and B react are they reacting because they are being driven to do so from below by the protons and electrons in their molecules Or are they reacting because of some property that is possessed by the two molecules at the chemical level of organization What is the direction of dependence It is by no means clear that reactivity is driven from below, that the chemical is dependent on the physical and not vice versa. If indeed the chemical levels determine the physical it is said that downward causation is taking place. 

McLaughlin takes the fact that there is now a highly successful quantum mechanical account of chemical bonding to indicate that the chemical level is dependent upon the physical and that physical forces bring about bonding at the chemical level. As may be seen in die above quotation McLaughlin takes this state of affairs to leave no room whatsoever for downward causation. 

Schrbder, J. 1998. "Emergence Non-Reducibility or Downwards Causation " Philosophical Quarterly, 48 433-452. 

It is relatively easy to talk and gesture about how chemistry either does or does not reduce to physics. It is much harder to spell out exactly what is required to make good on the claim that chemistry does (or does not) reduce to physics. Philosophers have a concept of supervenience. In the case we are focused on here chemistry putatively reducing to physics—supervenience requires that every chemical change be accompanied by a physical change. This is nearly universally held, for example, if two molecules are identical in all physical respects, they will not differ chemically. However, supervenience is not sufficient for the reduction of chemistry to physics. There could be downward causation, where it is the chemical facts and laws that drive the physical facts and laws, not the other way around. Robin Hendry (Chapter 9) argues that those committed to the reducibility of chemistry to physics have not ruled out the possibility of downward causation, and moreover, he presents substantial evidence from the manner in which quantum mechanical descriptions for molecules are constructed and deployed by chemists in favor of downward causation. Quantum mechanical descriptions of molecules that have explanatory and descriptive power are constructed from chemical—not physical—considerations and evidence. Here in precise terms, we see chemistry supervenient on physics, but still autonomous, not reducible to physics. 

This looks far more plausible the whole enterprise of quantum chemistry, after all, is to use quantum mechanics to recover facts about chemical bonding that are well known to the chemist. If there is meshing between chemistry and quantum mechanics, do the real meshes and interfaces we saw in the last section really support strict physicalism Surely they cannot, if they are consistent with downward causation. In any case, it is not as if, in the explanation of the spectrum of carbon dioxide, there are two independent theoretical accounts that were compared and found to be consistent. Perhaps that would constitute an explanation of the less fundamental models. But neither chemistry nor the quantum mechanics of resultant Hamiltonians have the resources for independent accounts of the spectrum of carbon dioxide. Rather than an explanation of chemical structure by physical theory there was a joint venture the explanation of various facts by the use of quantum mechanics applied to a given molecular structure. There was no mesh or interface between the quantum mechanics and chemistry, at least none that required explanation. What we had was an instance of quantum chemistry, the quantum theory of atoms and molecules.14... 

Note, however, that Kim s property identities are in themselves insufficient to rule out downward causation. What is required in addition is the causal completeness of physics with respect to systems within which the physical properties that realize these second-order properties are instantiated. 

Galaaen, O. S. (2006). The disturbing matter of downward causation. Dissertation, University of Oslo. 

Some authors go beyond this picture and see emergence as depending on downward causation (Hendry 2006). Others do not consider downward causation as a necessary condition for emergence (Batterman 2002). In this paper I will assume a fairly liberal concept of emergence - arguably, a theory which does not include downward causation can stiU be a theory of emergence if it talks about levels of reality which are dependent but autonomous from one another. 

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