Abstract

This paper defends the notion of downward causation. I will seek to elucidate this notion, explain why it is a useful way of thinking, and respond to criticisms attacking its intelligibility. My account of downward causation will be in many respects similar to the account recently advanced by Ellis. The overall framework I will adopt is the interventionist treatment of causation I have defended elsewhere: X causes Y when Y changes under a suitable manipulation of X. When X is at a higher “level” than Y this allows for the possibility of downward causation from X to Y. True claims of downward causation must meet certain additional conditions, some of which have already been discussed by Ellis. These include the condition that X must have a homogenous effect on Y in the sense that the effect of X on Y must be the same regardless of how X is “realized” at lower levels. In addition, the most plausible examples of downward causation will involve causes X, that in a sense that I will try to specify, are capable of being manipulated by macro-level interventions that have a coordinated or organized impact on them, as when one manipulates the temperature of a gas by placing it in a heat bath.Three common criticisms of the notion of downward causation that I will consider are: the claim that this involves a whole acting downward on its parts which is an objectionable idea because wholes and parts are not sufficiently distinct to stand in causal relationships, that downward causation commits us to the existence of causal cycles in which X causes Y which in turn causes X and that the asymmetric nature of the causal relation rules out such cycles, and causal exclusion type worries, according to which all of the causal action occurs among “low level” variables, so that upper level variables are deprived of causal efficacy. In response I will argue that plausible examples of downward causation in the scientific literature do not involve whole to part causation, there is nothing wrong with causal cycles, which are common in, for example, biological contexts, exclusion type worries do not arise within the interventionist framework that I favor.