Emergence of a higher level system from the lower level modules takes place when reliable higher level behaviour arises out of the lower level actions taking place in the context of this structure, with lower level units grouped together to form higher level modules that one can identify as meaningful entities that persist over time and have identifiable laws of behaviour. The way they interact with each other at a specific level can be characterized by an interaction network showing which modules interact with which other modules through various possible interaction modes (inter-module forces, or matter, energy and information exchange) this is the structure of the system. The internal dynamical variables are hidden from outside view external entities interact with the module through interface variables linked to the internal variables.Д®xamples are nuclei in atoms, cells in a human body, individuals in society and subroutines in a computer program. Each level of the hierarchy is made up of interacting modules that are relatively strongly bound internally, with higher frequency and higher energy internal dynamics, interacting with other modules through weaker bonds and lower frequency interaction dynamics. There is a similar hierarchy for artificial systems -language, mathematics, computers, aircraft, cities, organizations, societal roles, for example-that is not given here. The result is a highly structured hierarchy of interacting entities.ДЄ simplified version of the basic hierarchy of complexity and causality for natural systems (left) and for human beings (right) is given in table 1. The modules at each level will interact with each other in some way: maybe just statistically, if they all carry out the same task, or maybe in the form of a complex interaction network, when each of them will generally carry out different tasks. This is the level where the real work is done, each of these components feeding its results into the next higher level components until the desired result emerges at the appropriate higher level. Each module is again split up into submodules until you reach a base level where the necessary tasks are simple operations that can be carried out by simple mechanisms. The basic principle is that when you have a complex task to perform, you break it up into subtasks that are each simpler than the overall project, requiring less data and less computing power, and assign these tasks to specific modules. Each of these aspects (вЂmodularвЂ™, вЂhierarchicalвЂ™ and вЂstructureвЂ™) is crucial in the emergence of complexity out of interactions between simpler units. The basis of complexity is modular hierarchical structures, leading to emergent levels of structure and function based on lower level networks. How is this possible? How can our own lives emerge from interactions of electrons, protons and neutrons? Physics underlies all complexity, including our own existence. In both cases, an ongoing battle between bottom-up and top-down approaches has important consequences for society. Two cases will be mentioned: medical/healthcare issues, and education-in particular, teaching reading and writing.

Understanding top-down causation can have important effects on society.

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. Through the mind, abstract entities such as mathematical structures have causal power. 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). Five essentially different classes of top-down influence can be identified, and their existence demonstrated by many real-world examples. 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. Both bottom-up and top-down causation occur in the hierarchy of structure and causation.

Causality pronunciation