INUS condition

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The INUS condition was introduced by the Australian philosopher John Mackie . Within the framework of a regularity theory of causality, it should explain the concept of cause more precisely . INUS stands for " i nsufficient, but n ecessary part of a larger and nnecessary but s ufficient condition ", in German about, not sufficient , but necessary part of an unnecessary but sufficient condition '.


David Hume developed an understanding of causality that is now referred to as Humean metaphysics . To explain a cause-and-effect relationship, he introduced the concept of necessary and sufficient conditions and put forward the thesis that there are no necessary causal connections in the world because only spatially adjacent events can be observed in chronological order. According to Hume, we can only use our experience to identify causes and effects , with which we can describe regularities or regulations. Conclusions about future events are therefore never completely certain, but only probable .

Humean understanding of causality is only applicable to monocausal relationships. John Mackie's extension, on the other hand, also enables connections with multi- causality to be recorded. Today's theories of regularity of causality mostly use the INUS condition to do justice to the idea of ​​multiple causes and effects of an event.


As an illustrative example Mackie makes a house fire in which by an electrical short circuit caused , but overall only by the interaction of short-circuit and adjacent combustible material conditions is. It shows how the statement "the short circuit is the cause of the fire effect" is to be understood according to the INUS condition:

  • The short circuit is not a sufficient part of the condition “short circuit and combustible material” because it does not necessarily fulfill the condition on its own.
  • The short circuit is a necessary part of the “short circuit and combustible material” condition, because without it the condition cannot be met.
  • “Short circuit and combustible material” is not a necessary condition for a house fire because it can also be replaced by other conditions (e.g. “ lightning strike and combustible material” or “ arson ”).
  • “Short circuit and combustible material” is a sufficient condition for a house fire because it inevitably leads to the effect of the fire.

This example can be expanded enormously, the more factors and, above all, potential factors are taken into account. For example, “no sprinkler system ”, “no lightning rod ” or “no person in the house capable of extinguishing ” can be added to the condition. According to Mackie, a cause is always a partial condition for one or more effects to come about.

The prerequisite for the INUS condition is always regularity based on experience. Only when it has been observed several times that the condition "electrical short circuit and combustible material" has led to the effect "house fire" can one speak of a short circuit as the cause according to Mackie and predict with sufficient probability that short circuits in connection with combustible material will lead to a house fire to lead.


  • Wolfgang Detel : Basic Philosophy Course. Volume 2: Metaphysics and Natural Philosophy. Reclam, Stuttgart 2007 (Universal Library, 18469), ISBN 978-3-15-018468-4 , p. 74 f. ("INUS analysis of causation").
  • John Leslie Mackie: Causes and Conditions. American Philosophical Quarterly . 1965, 2 (4). pp. 245-264. .
  • John Leslie Mackie: The Cement of the Universe: A Study of Causation . London 1974: Oxford University Press. [Esp. Chapter 3: Causal Regularities, pp. 59-87].

Individual evidence

  1. ^ John Mackie: Causes and Conditions , published in the American Philosophical Quarterly , Volume 2, 1965, pp. 245-264
  2. Michael Esfeld: Causality , published in Andreas Bartels, Manfred Stöckler (Ed.): Wissenschaftstheorie , mentis Verlag, Paderborn 2009, p. 89 ff.