title: Top-down causation and emergence: some comments on mechanisms.
abstract: Both bottom-up and top-down causation occur in the hierarchy of structure and causation. A key feature is multiple realizability of higher level functions, and consequent existence of equivalence classes of lower level variables that correspond to the same higher level state. Five essentially different classes of top-down influence can be identified, and their existence demonstrated by many real-world examples. They are: algorithmic top-down causation; top-down causation via non-adaptive information control, top-down causation via adaptive selection, top-down causation via adaptive information control and intelligent top-down causation (the effect of the human mind on the physical world). Through the mind, abstract entities such as mathematical structures have causal power. The causal slack enabling top-down action to take place lies in the structuring of the system so as to attain higher level functions; in the way the nature of lower level elements is changed by context, and in micro-indeterminism combined with adaptive selection. Understanding top-down causation can have important effects on society. Two cases will be mentioned: medical/healthcare issues, and education-in particular, teaching reading and writing. In both cases, an ongoing battle between bottom-up and top-down approaches has important consequences for society.
authors: Mathematics ,  University of Cape Town ,  Rondebosch, Cape Town, Cape ,  South Africa.
authors: George F R
authors: GF
authors: Ellis
keywords: adaptive selection; emergence of complexity; top down causation
references: Nature. 2010 Sep 9;467(7312):167-73
references: 20829787
references: Interface Focus. 2012 Feb 6;2(1):101-14
references: 23386965
references: Nat Rev Genet. 2004 Feb;5(2):101-13
references: 14735121
references: BMJ. 2002 Feb 2;324(7332):288-90; discussion 290-4
references: 11823364
references: Interface Focus. 2012 Feb 6;2(1):55-64
references: 23386960
references: Annu Rev Psychol. 2005;56:25-56
references: 15709928
references: J R Soc Interface. 2008 Oct 6;5(27):1159-72
references: 18319208
references: Nature. 2011 Jun 22;474(7352):498-501
references: 21697947
references: Proc Natl Acad Sci U S A. 2011 Sep 13;108 Suppl 3:15588-95
references: 21383192
references: Interface Focus. 2012 Feb 6;2(1):26-41
references: 23386958
references: Nature. 2011 Mar 10;471(7337):151-3
references: 21390105
references: PLoS One. 2011 May 04;6(5):e18712
references: 21573231
references: Nature. 2011 Jun 15;474(7351):272-4
references: 21677723
references: Interface Focus. 2012 Feb 6;2(1):4-12
references: 23386955
references: J Neurosci. 2008 Oct 1;28(40):10056-61
references: 18829963
references: Public Health Rep. 1980 Jul-Aug;95(4):307-12
references: 6999524