Contingency, Constraints and the Boundaires of Explanation

A commentary on “the contingency theses”

Vivette García DeisterPhD Student

UNAM

What am I commenting on? Commentary

Of the contingency literature spurred (in part) by Beatty (1995)

In the light of Hamilton’s (2005) critiques

As a means to point to the repercussion of contingency-centeredness

For the problem of drawing the boundaries of explanation

Overview Commentary has two parts:

1. Review part of the contingency literature (using Beatty and Hamilton as book ends)

2. Suggest that the constraints literature can inform the discussion about how to draw the boundaries of explanation

Prelude: the “contingency theses”

There is a problem with drawing the boundaries of explanation by way of laws

The contingent-necessary dichotomy is misinformative about the power/depth/scope of a generalization

Contingency plays an important role in scientific explanations

There are better and worse ways of representing contingency and incorporating it in explanations

Part 1: Review of the contingency literature Beatty’s thesis, captured in his most

often-cited passage, is this: “[A]ll distinctively biological

generalizations describe evolutionarily contingent states of nature…This means that there are no laws of biology. For, whatever ‘laws’ are, they are supposed to be more than just contingently true” (Beatty 1995, p. 46).

Part 1: Review of the contingency literature Two authors address Beatty’s

concerns and conclusions in ways that are particularly informative to the problem of how to draw the boundaries of explanation: Sandra Mitchell (2003) James Woodward (2003)

Part 1: Review of the contingency literature Mitchell takes up Beatty’s verdict

about biology’s failure to produce scientific laws due to contingency

She replaces the accidental-necessary dichotomy with the contingent-stable continuum Pragmatic laws

Part 1: Review of the contingency literature Hamilton (2005) has detected a

patent difficulty in comparing degrees of stability when drawing a continuum, “since it is not clear how to compare the degree of stability of regularities in any fine-grained or principled way” (Hamilton 2005, p. 69). Problem of commensurability

Part 1: Review of the contingency literature Woodward explores the

implications that Beatty’s conclusion has for an account of explanation Move away from the nomothetic

conception of explanation “Invariance is the kind of stability that

matters”

Part 1: Review of the contingency literature Woodward’s account only applies

to mathematical representations of systems that can be manipulated and intervened upon in principle Problem of tractability

Expanded by Waters (2005) to investigative strategies in genetics

Explored by Mitchell (2005) in the context of developmental research programs

Part 1: Review of the contingency literature Notions of constraint

Beatty, Mitchell: contingency draws the boundaries of explanation by limiting constraining the attainment of laws

Nomic inhibition (Hamilton 2005) Woodward: account of explanation

should comply with epistemological constraints

Modular representation (Hamilton 2005)

Interlude: lessons learned The strategy for drawing the

boundaries of explanation is not the strategy for asessing the attainment of laws

Contingency-centeredness presents commensurability/tractability difficulties

Footnote Commensurability Qualitative

aspects of contingency (Martínez, tomorrow night)

Tractability We could benefit from a robust account of abstraction (Winther, tonight)

Part 2: taking constraints seriously Motivations for the focus on

constraints (1) Originates with a project that is

meant to limit the power of natural selection as the canonical cause of evolution

Project of drawing the boundaries of explanation by assessing causal roles, rather than nomic roles

Part 2: taking constraints seriously Motivations for the focus on

constraints (2) Literature on constraints takes

evolutionary contingency into account in a non-trivial sense according to which the origin of constraints is itself evolutionarily contingent and accounts for their taxon specificity

Part 2: taking constraints seriously Motivations for the focus on

constraints (3) For over two decades,

representatives of the constraints literature have engaged and tackled the problem of commensurability/tractability

Part 2: taking constraints seriously Identifying sources of constraint and

means to distinguish among them (e.g., Alberch 1982, Maynard-Smith et. al., 1985)

Recommending ways to establish and test constraint hypothesis (e.g., Alberch 1985, Vogl and Riensel 1991)

Developing methods for their quantitative assessment (e.g., Cheverud et. al. 1985)

Evaluating their feasibility and explanatory power (Mary McKitrick 1993)

Part 2: taking constraints seriously Ongoing debate is not merely

terminological What is the relationship between

selection and constraint? Limits of selection as cause or as

restriction of phenotypic change Causal contribution of constraints

Part 2: taking constraints seriously First strategy: conceptual

separation Constraints are seen “as manifested

in their effects on selection, implying that constraint is one thing and selection another” (Schwenk and Wagner 2003, p. 53)

Endorsed by Maynard-Smith et. al.’s (1985) notion of developmental constraints

Part 2: taking constraints seriously Developmental constraints are

“biases on the production of variant phenotypes or limitations on phenotypic variability caused by the structure, character, composition, or dynamics of the developmental system” which “undoubtedly play a significant role in evolution” (Maynard-Smith et. al. 1985, p. 265)

Part 2: taking constraints seriously Second strategy: conflation

Consists in “identifying constraint with a particular evolutionary outcome or pattern,” thus concluding that “the responsible mechanism is, by definition, ‘constraint’” (Schwenk and Wagner 2003, p. 53)

McKitrick’s (1993) notion of phylogenetic constraints endorses/emends this view

Part 2: taking constraints seriously Phylogenetic constraints are

“any result or component of the phylogenetic history of a lineage that prevents an anticipated course of evolution in that lineage” (McKitrick 1993, p. 309)

Part 2: taking constraints seriously Proponents of both the separation and

conflation approaches agree that: There is a void in the explanatory work

that selection can (should?) do and a notion of constraint is bound to occupy it

There are epistemological requirements of constraint tractability that must be met by a working definition of constraint

Part 2: taking constraints seriously Proponents of both the separation

and conflation approaches agree that:

A working definition of constraint must refer to local mechanisms (or processes) examined at a specified developmental stage and they must apply to a limited range of taxa

The acquisition of constraints is itself evolutionarily contingent

Part 2: taking constraints seriously Schwenk and Wagner´s (2003) analysis

of the separation strategy “[T]he failure to generate phenotypic

variability during development cannot be temporally or mechanistically separated from the action of selection” (p. 54)

“[A] dichotomous approach leads to a highly restrictive notion of constraint that does not satisfy the needs of many evolutionists for a constraint concept” (p. 54)

Part 2: taking constraints seriously Schwenk and Wagner´s (2003) analysis

of the conflation strategy Sympathetic towards it, provided that the

circumstances in which selection acts as a constraint are specified contextually

By establishing a set of fixed points (specifying factors) around which constraint can be organized, they propose a strategy to draw the boundaries of operation of constraint and outline its explanatory power

Preliminary conclusions Pointed to an ongoing debate in

biology where a strategy for drawing the boundaries of explanation is being sought

Debate addressed by both biologists and philosophers of biology

Preliminary conclusions Proposed strategy is not meant to

solve the commensurability/tractability difficulties of contingency

Engages and tackles these difficulties in its own domain

It does not shelve Beatty’s evolutionary contingency thesis

More coming up

If you want to know what constraints can do for the contingency literature, stick around for Sandra Mithchell’s talk, after lunch...

Acknowledgements CONACYT project 41196-H:

Filosofía de las prácticas científicas, for funding

Members of the Griesemer lab at UC Davis, for input

Sergio Martínez and Andrew Hamilton, for discussion

You, for attending this session