Reasoning under uncertainty methods

In reasoning about or under uncertainty it is sometimes not enough to use the best method, or an accredited method: one needs to understand the limitations of method.

The limits of method

Strictly, rational reasoning implies that everything can be assigned a value and probability, so that the overall utility can me maximised. So when faced with greater uncertainties, the appearance of rationality can only achieved by faking it, which is not always effective.

Pragmatism is more general than rationalism. The key feature is that one uses a fixed model until it is no longer credible. But if the situation is complex or uncertain it may not be possible to use a definite model without making unwarranted assumptions.

Turing (a grand-student of Whitehead) demonstrated some of the limitations of definite methods more generally. We cannot be too restrictive in we consider to be ‘methodical’.

One approach to method is to link overall decisions to ‘objective’ sub-decisions, made by accredited specialist decision-makers. This relies on some conceptual linkage between the specialists and generalists, and between all collaborators on a decision. This can deal with complicatedness across specialisms and complexity and uncertainty within specialisms, in so far as they are understood across the specialisms.

The difficulty with this approach is that complexity and uncertainty often span the whole domain. One is thus left with the problem of handling complexity and uncertainty within a collaboration.


It follows from the Conant-Ashby theorem that people who are good at dealing with complexity and uncertainty without having dominance must, in some sense, understand these topics, even if they have had no exposure to the relevant theories. This raises these questions:

  • How do we recognize people whose track records are such that we can be sure that they have the appropriate understanding, and weren’t reliant on others or lucky?
  • To what extent can is an understanding of complexity and uncertainty developed in one situation relevant to another? Are all complexities and uncertainties in some sense similar, or amenable to the same approaches?
  • How can such understanding and methods be communicated?

Way ahead?

The following have been found helpful in confrontation, crisis and conflict anticipation and management:

  • Developing the broadest possible theoretical base for complexity and uncertainty, using Keynes’ Treatise as a former.
  • Identifying and engaging as broadly and fully as possible with all parties to the situations (of whatever nationality etc) who show an understanding or ability to handle complexity and uncertainty.

More broadly, seeking to take an overview and engagement with practitioners who are engaged with the more challenging kinds of complexity and uncertainty, with the aim of developing practical aids to comprehension:

  • To assist those who are or may be engaged
  • To help develop understanding among those who could support those who are or may be engaged.
  • To help establish some common language etc so that the broadest possible community can have the fullest possible visibility and understanding of the process, and – where appropriate – involvement.

The core of all this would seem to be a set of resources that address complexity and uncertainty rather than complicatedness and probability, with understanding to be developed via collaborative ‘war-games’.

Pedagogic resources

The aids included in the following have proved helpful.

  • Peter Allen’s overview, allows an appreciation of most of the fields.
  • Everyday and other metaphors.
  • A Whitehall report on collaboration highlights complexity and uncertainty, including in the ‘collaborative partnership model’.
  • SMUTS, supporting exploration of key factors.

See Also

How much uncertainty?, HeuristicsKnightian uncertainty , Kant’s critique.

David Marsay


About Dave Marsay
Mathematician with an interest in 'good' reasoning.

2 Responses to Reasoning under uncertainty methods

  1. Pingback: Examples of Uncertainty in Real Decisions | djmarsay

  2. Pingback: Out of Control | djmarsay

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