What is a mechanism? thinking about mechanisms across the sciences

Citation: Illari PM, Williamson J (2012) What is a mechanism? thinking about mechanisms across the sciences. Eur J Philos Sci 2:119–135 (RSS)
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Summary

Illari and Williamson define mechanisms as entities and activities organized in certain ways to produce a phenomenon. The organization of a mechanism is important, as different arrangements of entities and activities can result in entirely different phenomenon. This article discusses mechanisms in the context of a mechanistic approach to causality, in an effort to contribute to the debate on the utility of mechanisms in explanatory theory. The authors use astrophysics mechanisms as an example of the wide applicability of mechanisms to scientific explanations.

According to Illari and Williamson, all mechanisms begin with first identifying the phenomenon to be described, decomposing the entities and activities relevant to that phenomenon, and lastly organizing those components in such as way as to produce the same phenomenon (thereby verifying the arrangement of those components in the creation of that phenomenon. The authors see this an iterative process. An explanation succeeds when a mechanism (and the three stages discussed above) fully explain the phenomenon.

The two components of a mechanism, entities and activities, are named as such to prevent entity-bias or limiting the number of variables that can be compose activities. Entities are the bits and pieces of the mechanism, and activities are what those bit and pieces do, which organization of those bits and pieces describes how they interact to produce the phenomenon. The size of the entity can vary, and some mechanisms are composed of very fragile entities and activities.

The authors caution that sometimes, despite scientific advancements, the description of a mechanism will remain partial. It is also important to remember that not every variable can be a mechanism. Mechanisms may also not be a "smaller" method of describing the phenomenon (in its smallest parts). The mechanism by which genes segregate, for example, does not require decomposing all genes down to their chromosomes to understand that phenomenon.