5.1 Simple (purposive) and complex (purposeful) systems
Spend a few minutes reading through the table and then do the activity that follows.
| Situations regarded as simple ‘purposive systems’ | Situations regarded as complex ‘purposeful systems’ |
| Have predictable behaviour; e.g. a fixed interest bank account. | Generate counterintuitive, seemingly acausal behaviour that is full of surprises; e.g. lower taxes and interest rates leading to higher unemployment. |
| Few interactions and feedback or feed forward loops; e.g. a simple barter economy with few goods and services. | A large array of variables with many interactions, lags, feedback loops and feed forward loops, which create the possibility that new, self-organising behaviours will emerge: e.g. most large organisations, life itself. |
| Centralised decision-making; e.g. power is concentrated among a few decision makers. | Decentralised decision-making – because power is more diffuse, the numerous components generate the actual system behaviour. |
| Are decomposable because of weak interactions; i.e. it is possible to look at components without losing properties of the whole. | Are irreducible – neglecting any part of the process or severing any of the connections linking its parts usually destroys essential aspects of the system behaviour or structure. There are dynamic changes in the system and the environment. |
Footnotes
(Adapted from Casti, 1994, pp. 271–3)Activity 3 Reflections on categorisations
In the original version of Table 1, Casti ascribed the terms simple and complex to the word systems. Write down your answers to the following questions:
- In what ways do you experience the terms ‘systems’ and ‘complex’ being used by Casti?
- What implications might these categories have for systems practice?
- How does the revision of the two categories alter in any way, if at all, your understandings of the terms ‘complexity’ and ‘systems’?
Comment
The purpose of this activity was to invite you to reflect on what it is that we do when we categorise anything. One way of reading this table is as a set of two categories each containing different category members. The mechanism employed in this categorisation is to add an adjective in front of the noun ‘system’. So they are different categories of system. This is the same process as developing a typology. Of course this is something we do all the time but I do not think we reflect very often on the implications of doing this! The implications for systems practice are discussed next.
The questions in Activity 3 are extremely interesting but at the same time potentially confusing. The word ‘complex’ is being used by Casti in some cases to mean the same as ‘system’, and some of the characteristics of complexity seem to be applied to system. The phrase ‘complex system’ is common, although the meaning attributed to it is often unclear. For example, it might be unclear whether Casti is using ‘system’ in its everyday sense or in the specific way it is used within the study of systems to mean a system of interest to someone.
When you consider the examples used in Table 1 there is something qualitatively different about a simple barter economy and the phenomenon of lower taxes and interest rates leading to higher unemployment other than whether they can be described as simple or complex. Indeed, you might question whether it would be helpful to consider a barter economy as simple. Considering the quality of relationships and trust that might be necessary to sustain a barter economy, it could be perceived as complex. This notion of quality of relationship is an important additional distinction that could be attributed to complexity over that provided in the earlier list of Schoderbeck et al. (1985) in Week 2 which tends to focus only on the quantity of variables or interactions.