Post on 17-Dec-2015
transcript
Two approaches to mechanisms (Glennan 2002)
higher levelslevel of physics
thing, with stable dispositions
sequence of singular events
MDC, GlennanSalmon, Dowe
complex-system approachprocess approach
c-s mechanisms and difference-making
• several papers dealing with the relationship between c-s mechanisms and causality as counterfactual dependence (Woodward 2002, Psillos 2004, Glennan 2009)
• question: is it mechanisms or counterfactuals that are fundamental?
p mechanisms and counterfactuals
• Counterfactuals involved in the definitions of mark transmission and of causal interaction in Salmon 1984
• Reference dropped in Dowe and Salmon 1994: conserved quantity theory
Questions
• Can't we say something more concerning the relationship between p mechanisms and– counterfactuals – more generally, difference-making?
• Remark: p mechanisms / c-s mechanisms vs. possible / impossible to explain “genuinely singular events” (Glennan 2002)
Approach
• Focus on propensities
• Justification: – provide the only physical interpretation for
probabilities of singular events– have to do with p mechanisms
• NB. One goal of the talk is to explicate this justification.
Outline
1. Propensities and p mechanisms
2. Propensities and difference-making
3. p mechanisms and difference-making
Outline
1. Propensities and p mechanisms
2. Propensities and difference-making
3. p mechanisms and difference-making
Popper’s propensity theory
• An objective, physical interpretation of singular probabilities
• Propensities as tendencies of physical situations to produce singular events
• Physical reality of propensities• Probabilities as measures of propensities
Propensities and processes
• Ontological similarities: physically real, dynamic / active, causally productive, somehow continuous
• Yet no identity of (some) processes with propensities: processes ≠ tendencies
Salmon (1984) on propensities and processes
• Propensities = probas that are carried by indeterministic causal processes (203)
• Problems:- difficult to express in terms of conserved
quantities- misses the Popperian probability / propensity
distinction
Dowe (1992) on propensities and processes
• “propensities should be regarded as referring to the operation of indeterministic causal processes and interactions” (213)
• Relies only on (Popperian) propensities being attached to the level of physics
• Implies there are no propensities (although there may be objective, physical probas) but at the level of physics
Outline
1. Propensities and p mechanisms
2. Propensities and difference-making
3. p mechanisms and difference-making
Probabilistic causality
• Analyses of causality in terms of inequalities between absolute and conditional probabilities
• At the level of physics, problem with the interpretation of conditional probabilities
Humphreys' paradox (1985)
• (CI):if p(A / B) is temporally inverse and p is given
a propensity interpretation,then p(A / B) = p(A / non-B) = p(A)
• logically incompatible with the calculus of probability
• conclusion: no propensity interpretation of conditional probabilities.
Against HP
• Justification of (CI): if p(A / B) is inverse, impossible for the propensity tending to realize A to be (physically) modified by the occurrence of B
• But: according to the propensity theory, the production relation is between a physical situation and sg events, not between two sg events (conditioning and conditioned).
Towards a propensity interpretation of p(A / B)
• Conditionalization as a modification of p• A propensity interpretation tells how a new
probability function, meaning a new physical situation, is defined out the initial one and B
• The definition can be such that the properties of conditionalization are accounted for
• Csq: one can define probabilistic notions of singular causality at the level of physics
Link with counterfactuals
• The new situation has to be different from the initial, actual one, i.e. p(A / B)- measures the propensity of a counterfactual
situation to produce A- measures a counterfactual propensity to produce
A- is a counterfactual probability
• At the level of physics, notions of probabilistic causality collapse into counterfactual analyses.
Outline
1. Propensities and p mechanisms
2. Propensities and difference-making
3. p mechanisms and difference-making
What I have claimed
• propensities pertain to the level of physics and they refer to indeterministic causal processes and interactions
• probabilistic causality can be defined at this level and in terms of propensities, and there it collapses with the counterfactual approach
p mechanisms and difference-making
• p mechanisms are more fundamental than difference-making:• they give reference to the propensity talk• propensities are needed to ground a
difference-making notion of singular physical causality
• Conceptual and ontological priority
Scope
• Not a conclusion specific to p mech.• A conclusion
– about mechanisms and difference-making at the same level
– concerning mechanisms• What is specific to p mechanisms:
– irrelevance of the debate concerning counterfactuals and characterizations of mechanisms
– problem with the interpretation of conditional probabilities.