Introduction to mechanisms

1. Mechanisms in the Sciences:
A Field Guide
Federica Russo
Center Leo Apostel, VUB
Centre for Reasoning, Kent

2. Overview
1. The received view 6. Evidence of mechanisms
2. The consensus 7. Mechanisms and
3. Why mechanisms? reasoning
4. Mechanisms on the stage 8. Pluralism and monism
5. What are mechanisms for? 9. Practical (scientific) use
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3. 1
THE RECEIVED VIEW
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4. Machamer, Darden and Craver:
‘Mechanisms are entities and activities organized such that they are
productive of regular changes from start or set-up to finish or
termination conditions.’ (Machamer, Darden and Craver 2000 p3.)
Glennan:
‘A mechanism for a behavior is a complex system that produces that
behavior by the interaction of a number of parts, where the
interactions between parts can be characterized by
direct, invariant, change-relating generalizations.’ (Glennan 2002b
pS344.)
Bechtel and Abrahamsen:
‘A mechanism is a structure performing a function in virtue of its
component parts, component operations, and their organization.
The orchestrated functioning of the mechanism is responsible for
one or more phenomena.’ (Bechtel and Abrahamsen 2005 p423.)
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5. 2
THE CONSENSUS
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6. Illari& Williamson:
A mechanism for a phenomenon is composed of entities
and activitiesorganized so that they are responsible for the
phenomenon.’ (2012, p.120)
Illari& Williamson give up on:
Regularity
Start up, finishing conditions
Complex system
Mechanistic explanation:
Identification of the phenomenon
Identification of entities and activities involved
Identification of the organisation
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7. 3
WHY MECHANISMS?
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8. Once upon a time: process theories
Causation in physics
Salmon-Dowe approach
A development of Russell-Reichenbach
(world-lines, at-at theory)
Salmon: ‘put the cause into because’
The because is given by the physical, causal process
(Ontic explanation)
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9. Processes in biology?
MDC (2000, p. 7):
Although we acknowledge the possibility that Salmon’s
analysis may be all there is to certain fundamental types
of interactions in physics, his analysis is silent as to the
character of the productivity in the activities investigated
by many other sciences. Mere talk of transmission of a
mark or exchange of a conserved quantity does
not exhaust what these scientists know about
productive activities and about how activities effect
regular changes in mechanisms.
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10. Processes in social science?
Russo (2009, p.26):
The need to look directly at social scientists’ work was motivated by a
possible difference between causal claims that involve reasonably clear
causal mechanisms and causal claims that do not. I went through five case
studies, and it turned out that none of them contains concepts typical of
aleatory causality in order to get an understanding of causal relations—to
borrow Salmon’s terminology again. Instead, statistical causality is
definitively preferred. However, to prefer statistical causality does not ipso
facto rule out mechanisms from the causal talk. […] the question is not
whether or not we aim at identifying causal mechanisms, rather, how do
we come to identify them. Causal mechanisms are not identified
through causal processes and interactions, but, according to the
social scientists’ practice, they are statistically modelled.
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11. 4
MECHANISMS ON THE STAGE
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12. Biology and neuroscience
Bechtel, Craver, Darden, MDC, …
Functional individuation
Mechanistic explanation
Decomposition / re-composition
…
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13. Social science
Analytical sociologists, Little, Russo (&Mouchart,
Wunsch), …
Mechanisms and
Methodological individualism
Statistical modelling
Social regularities
Human action
Social ontology
…
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14. 5
WHAT ARE MECHANISMS FOR?
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15. Explanation
Ontic and epistemic mechanistic explanations
Craver, Bechtel (biology / neuroscience)
Illari: ‘reconciliation’ of the ontic and epistemic
Russo et al (social science)
Explain … how?
Organisation, recursive decomposition
Backwards, downwards, or upwards
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16. Self-rated health in the Baltic countries 1994-1999
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17. What are the causes of self-rated health in the Baltic countries
in the ‘90s?
X Y
Take the joint probability distribution + Make assumptions
P(Education, Locus of Control, Physical Health, …, Self-Rated Health)
P(X1, X1, X3, …Y)
perform a recursive decomposition of the type
P(Y)= P(X1) P(X3) P(X2|X3) … P(Y|X2, X3)
Read as:
Self-Rated Health depends on Education; on Locus of Control through
Psychological distress; on Alcohol Consumption which also depends on
Physical Health; …
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18. Speaking of ‘upwards’
Darden:
Often biologists engage in much investigative work to discover the
level at which a given mechanism operates. Geneticists worked to
find the operative level for genetic linkage, ruling out the coupling
of paired alleles and the reduplication of germ cells and ruling in
chromosomal mechanisms (Darden 1991). Genes are linked
because they ride along on chromosomes in meiotic mechanisms.
In immunology, the working entities in clonal selection were at first
hypothesized to be self-replicating protein molecules but were later
found to be self-reproducing immune cells (Darden 2006, Chapter
8). These two examples show that biologists do not
always discover working entities in mechanisms by
going to a smaller size level; sometimes the operative
units are intermediate or larger than at first
hypothesized: not genes but chromosomes, not molecules but
cells. (2008, p. 961)
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19. Causal assessment
The (in)famousRusso-Williamson Thesis
To establish a causal claim we typically need
evidence of mechanisms and of difference-making
An epistemological thesis about
evidence for causal claims
First formulated for the health sciences,
but can be extended to other sciences
See however criticisms in the literature
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20. Arguments for RWT
Medical practice (IARC)
History of medicine (Semmelweis)
Epidemiology guidelines (Hill)
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21. 6
EVIDENCE OF MECHANISMS
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22. “Disambiguating RWT”
Evidence of difference-making
Evidence ofmechanisms
Plausible mechanisms, rather than confirmed
Methods generating the evidence vs evidence itself
Difference-making / Mechanisms
A conceptual distinction
In practice, highly intertwined
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23. 7
MECHANISMS AND REASONING
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24. Howick:
Mechanistic reasoning: involves an inference from
mechanisms to claims that an intervention
produces a patient-relevant outcome. Such
reasoning will involve an inferential chain linking the
intervention (such as antiarrhythmic drugs) with a
clinical outcome. (2011, p.128)
[…] If, as Russo and Williamson appear to argue,
mechanistic reasoning is required to establish causal
claims, then it is reasonable to doubt the causal claim
supported by strong comparative clinical studies. […]
My argument is that mechanistic reasoning is not
necessary to establish causal claims. (p.131)
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25. Spot the odd-man out
Causal assessment is based on evidence;
The evidence required concerns:
Mechanisms
Difference making
Mechanistic reasoning
Inferential
Not just about linking
interventions and clinical outcomes
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26. Nota bene …
Knowledge of mechanisms is never ‘complete’
Evidence is never ‘necessary’
The epistemological basis of causal assessment does
not always coincide with reasons for action
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27. 8
PLURALISM AND MONISM
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28. Conceptual pluralism and monism
Evidentialpluralism, conceptual monism
From RWT to the epistemic theory
Information theory? An account of production
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29. 9
PRACTICAL (SCIENTIFIC) USE
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30. Mechanisms in the evidence hierarchy
The evidence hierarchy:
the pillar of EBM
The role of mechanisms
(from top to bottom)
‘Reinforced concrete’
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31. Check out MatEH
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32. Diagnosis
Medical diagnosis
Diagnosis of dysfunction in organisational science
Enterprise Engineering and CIAO! network
Cooperation &
Interoperability -
Architecture &
Ontology
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33. CIAO! network
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34. Conceptualisation
‘EnviroGenomarkers’ Project
Mapping the evolution of biomarkers from exposure
to early clinical changes to disease development
A combination of processes and mechanisms
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35. EnviroGenomarkers project
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36. To sum up and conclude
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37. Mechanisms:
a (hot) field in phil sci
Reasons develop the field Mechanisms in contexts
A growing interest No mechanisms in
isolation
Important philosophical
distinctions No panacea
Great applicability to the Sharpening a conceptual
sciences tool for a better science
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