On the Nature of Causation in Complex Systems

A reliable understanding of the nature or causation is the core feature of science. In this paper the concept of top-down causation in the hierarchy of structure and causation is examined in depth. Five different classes of top-down causation are identified and illustrated with real-world examples. They are, 1. mechanical top-down causation; 2. top-down causation via non-adaptive information control; 3. top-down causation via adaptive selection; 4. top-down causation via adaptive information control; and 5. intelligent top-down causation (i.e. the effect of the human mind on the physical world). Recognising these forms of causation implies that other kinds of causes than physical and chemical interactions are effective in the real world. Because of the existence of random processes at the bottom, there is sufficient causal slack at the physical level to allow all these kinds of causation to occur without violation of physical causation. That they do indeed occur is indicated by many kinds of evidence. 1: CAUSATION AS THE CORE OF SCIENCE The nature of causation is a core issue for science, which can be regarded as the move from a demon-centered world to a world based on reliable cause and effect, tested by experimental verification (Sagan 1996). Causes are separated from effects by searching for correlations between phenomena such that manipulation of one (`the cause) can be shown, in a specific context, to reliably result in specific changes in the other (`the effect’) at a later time. One has to search for this correlation in the midst of internal and environmental noise (Pearl 2000). Laboratory tests of isolated systems allow an understanding of the elements of causation, which are interactions between the particles that underlie all physical existence; these interactions in multiple combinations underlie the emergence of complex phenomena such as life. Thus physics is the basic science, characterized by mathematical descriptions (Penrose 2005) that allow predictions of physical behavior to astonishing accuracy and underlies the other sciences (Feynman 1995, Chapter 4; Hewitt et al, 2007). The key question is whether other forms of causation such as those investigated in biology, psychology, and the social sciences are genuinely effective, or are they rather all epiphenomena grounded in purely physical causation? The latter view is suggested by strong reductionist views based in the fact that all physical entities we see around us, including ourselves, are based in the same chemical elements (Emsley 2003) composed from the same kinds of elementary particles, interacting with each other only through the four fundamental physical forces (Penrose 2005, Oerter 2006). How can there then be room for any other type of causation? 1 Mathematics Department, University of Cape Town, Rondebosch, Cape Town 7701, South Africa Email: [email protected] 2 http://en.wikipedia.org/wiki/Causality.