Models of Mechanisms: The Case of the Replicator Dynamics - Mechanism and Causality in Biology and Economics - page 82

a prototype mechanism, which is then judged to be sufficiently similar to the
mechanism that actually produced the phenomenon.
Yet this is not the only way how one can conceive of inferences between
mechanisms. Instead of restricting one's ontology to concrete mechanisms that
are only instantiated in one kind of organism, or one kind of social institution, one
might also accept that there are abstract mechanisms that have many concrete
instantiations in different kinds of organisms or institutions. This idea has been
floated by some writers, who propose a sort of hierarchy of mechanisms. It is
worthwhile quoting one such argument at length.

Processes identified in the causal reconstruction of a particular case or a class of macro-
phenomena can be formulated as statements of mechanisms if their basic causal structure
(e.g., a specific category of positive feedback) can also be found in other (classes of) cases.
The mobilization process observed in a fund-raising campaign for a specific project can, for
instance, be generalized to cover other outcomes such as collective protest or a patriotic
movement inducing young men massively to enlist in a war. A particular case of techno-
logical innovation like the QWERTY keyboard may similarly be recognized as a case in
which an innovation that has initially gained a small competitive advantage crowds out
technological alternatives in the long run. This is already a mechanism of a certain
generality, but it may be generalized further to the mechanism of “increasing returns,”
which does not only apply to technological innovations but has also been used in the
analysis of institutional stability and change “Increasing returns,” of course, is a

subcategory of positive feedback, an even more general mechanism that also operates in
the bankruptcy of a firm caused by the erosion of trust or in the escalation of violence in
clashes between police and demonstrators. (Mayntz 2004 , p. 254)

...

Central to this idea is that more abstract mechanisms exist in the same way as
concrete mechanisms are said to exist. Abstract mechanisms are instantiated in
more concrete mechanisms: Mayntz' positive feedback mechanism is instantiated
in escalation of violence between police and demonstrators, in trust-erosion
mechanisms and in increasing returns mechanisms. Mechanisms of different
degrees of abstraction are also nested : positive feedback is instantiated in increasing
returns, which in turn is instantiated in technological crowding out, which in turn is
instantiated in the specific process that led to the dominance of the QWERTY
keyboard.
According to this view, inferences between mechanisms do not go from
prototypes to similar particular mechanisms, but they go through abstract
mechanisms in the form of shared 'basic causal structure'. Explaining with a
mechanistic model commences by explaining the phenomenon with an abstract
mechanism and then showing that the mechanism that actually produced the
phenomenon is an instantiation of the abstract mechanism.
Allowing for abstract mechanisms produces an ontological mirror image to the
abstraction hierarchy of models. Unlike the exemplar account, which casts all
models as more or less abstract representations of particular mechanisms, the
abstract mechanism account allows models to represent both abstract and particular
mechanisms. Consequently, what appears at first sight to be a mechanism sketch
might either be an abstract representation of particular mechanisms or a nearly
complete model of an abstract mechanism.