Online research in philosophy

The idea of a higher level phenomenon having a downward causal influence on a lower level process or entity has taken a variety of forms. In order to discuss the relation between emergence and downward causation, the specific variety of the thesis of downward causation (DC) must be identified. Based on some ontological theses about inter-level relations, types of causation and the possibility of reduction, three versions of DC are distinguished. Of these, the `Strong' form of DC is held to be in conflict with contemporary science; the `Medium' version of DC may for instance describe thoughts constraining neurophysiological states, while the `Weak' form of DC is physically acceptable but may not in practice be a feasible description of the mind/brain or the cell/molecule relation. All forms have their specific problems, but the Medium and the Weak version seems to be most promising.

Several theories of emergence will be distinguished. In particular, these are synchronic, diachronic, and weak versions of emergence. While the weaker theories are compatible with property reductionism, synchronic emergentism and strong versions of diachronic emergentism are not. Synchronice mergentism is of particular interest for the discussion of downward causation. For such a theory, a system's property is taken to be emergent if it is irreducible, i.e., if it is not reductively explainable. Furthermore, we have to distinguish two different types of irreducibility with quite different consequences: If, on the one hand, a system's property is irreducible because of the irreducibility of the system's parts' behavior on which the property supervenes, we seem to have a case of "downward causation". This kind of downward causation does not violate the principle of the causal closure of the physical domain. If, on the other hand, a systemic property is irreducible because it is not exhaustively analyzable in terms of its causal role, downward causation is not implied. Rather, it is dubitable how unanalyzable properties might play any causal role at all. Thus, epiphenomenalism seems to be implied. The failure to keep apart the two kinds of irreducibility has muddled recent debate about the emergence of properties considerably.

Recent developments in nonlinear dynamics have found wide application in many areas of science from physics to neuroscience. Nonlinear phenomena such as feedback loops, inter-level relations, wholes constraining and modifying the behavior of their parts, and memory effects are interesting candidates for emergence and downward causation. Rayleigh–Bénard convection is an example of a nonlinear system that, I suggest, yields important insights for metaphysics and philosophy of science. In this paper I propose convection as a model for downward causation in classical mechanics, far more robust and less speculative than the examples typically provided in the philosophy of mind literature. Although the physics of Rayleigh–Bénard convection is quite complicated, this model provides a much more realistic and concrete example for examining various assumptions and arguments found in emergence and philosophy of mind debates. After reviewing some key concepts of nonlinear dynamics, complex systems and the basic physics of Rayleigh–Bénard convection, I begin that examination here by (1) assessing a recently proposed definition for emergence and downward causation, (2) discussing some typical objections to downward causation and (3) comparing this model with Sperry’s examples.

Philosophical accounts of emergence have been explicated in terms of logical relationships between statements (derivation) or static properties (function and realization). Jaegwon Kim is a modern proponent. A property is emergent if it is not explainable by (or reducible to) the properties of lower level components. This approach, I will argue, is unable to make sense of the kinds of emergence that are widespread in scientific explanations of complex systems. The standard philosophical notion of emergence posits the wrong dichotomies, confuses compositional physicalism with explanatory physicalism, and is unable to represent the type of dynamic processes (self-organizing feedback) that both generate emergent properties and express downward causation.

I outline reasons for the recent popularity, and lingering suspicion, about 'emergence' by examining three distinct concepts of property emergence, their purposes and associated obligations. In Part 1, I argue 'Strong' emergence is the grail for many emergentists (and physicalists), since it frames what is needed to block the 'Argument from Realization' (AR) which moves from the truth of physicalism to the inefficacy of special science properties. I then distinguish 'Weak' and 'Ontological' emergence, in Part 2, arguing each is a way one may fail to establish the possibility of Strong emergence. But I also show Weak emergence can help the full-blown reductionist and Ontological emergence helps those opposed to physicalism. Lastly, in Part 3, I argue that the Completeness of Physics (CoP) is incompatible with Strong emergence and that rejecting CoP provides hope for the possibility of Strong emergence in a physical world. The result is a notion of Strong emergence offering much to non-reductive physicalism. My final conclusion is that concepts of emergence, when properly understood, have important contributions to make to philosophical debate.

In the first section of this paper, I articulate Jaegwon Kim's argument against emergent down ward causation. In the second section, I canvas four responses to Kim's argument and argue that each fails. In the third section, I show that emergent downward causation does not, contra Kim, entail overdetermination. I argue that supervenience of emergent upon base properties is not sufficient for nomological causal relationsbetween emergent and base properties. What sustains Kim's argument is rather the claim that emergent properties realized by base properties can have no causal powers distinct from those base properties. I argue that this is false.

The dominant position in Philosophy of Science contends that downward causation is an illusion. Instead, we argue that downward causation doesn’t introduce vicious circles either in physics or in biology. We also question the metaphysical claim that “physical facts fix all the facts.” Downward causation does not imply any contradiction if we reject the assumption of the completeness and the causal closure of the physical world that this assertion contains. We provide an argument for rejecting this assumption. Furthermore, this allows us to reconsider the concept of diachronic emergence.

Weak emergence has been offered as an explication of the ubiquitous notion of emergence used in complexity science (Bedau 1997). After outlining the problem of emergence and comparing weak emergence with the two other main objectivist approaches to emergence, this paper explains a version of weak emergence and illustrates it with cellular automata. Then it explains the sort of downward causation and explanatory autonomy involved in weak emergence.