the conflation of “chance” in evolution
DESCRIPTION
Literature on the role of “chance” in evolutionary theory exhibits a dizzying array of claims – from “randomness” in genetic drift and mutation to “propensities” in fitness and “contingency” in macroevolution. I argue that much of this diversity is due to the persistent conflation of several senses of “chance,” and a corresponding failure to determine which sense is at issue in any particular biological instance. I offer an attempt to clarify and separate five of these senses: (i) the statistical or non-statistical character of a theory, (ii) the probabilistic or non-probabilistic character of a causal process, (iii) the determinism or indeterminism of underlying physics, (iv) the contingency or necessity of a historical process, and (v) the predictability or unpredictability of a particular system. I then conclude with an initial effort at showing how careful maintenance of these distinctions can enhance our understanding of the role of chance in evolution, by applying them to a few current debates in the philosophy of biology.TRANSCRIPT
University of Notre DameProgram in the History and Philosophy of Science
Department of Philosophy
The Conflation of “Chance”in Evolution
ISHPSSB ’11
Charles H. [email protected]
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved
• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates
• Show that conflation causes problems in arguments
An Argument in Two Parts
• Main Thesis: We ought to be more careful with our use ofchance in evolution
• Two objections:
• The philosophical debates are unresolved• The distinctions at work are merely semantic
• Two rebuttals:
• Distinguish four notions of “chance” without resolving
those debates• Show that conflation causes problems in arguments
Four Notions of “Chance”
“process” chance randomness
Four Notions of “Chance”
“process” chance randomness
subjective chance objective chance
unpredictability
Four Notions of “Chance”
“process” chance randomness
subjective chance objective chance
causal indeterminism probabilistic causal processes
unpredictability
Four Notions of “Chance”
• randomness
• unpredictability
• causal indeterminism
• probabilistic causal processes
• Not the only four!
Four Notions of “Chance”
• randomness
• unpredictability
• causal indeterminism
• probabilistic causal processes
• Not the only four!
Brandon & Carson
• “The Indeterministic Character of Evolutionary Theory”(1996)
• “drift clearly is a stochastic or probabilistic orindeterministic phenomenon” (324)
• “if one is a realist...then one should conclude that[evolutionary theory] is fundamentally indeterministic”(336)
Brandon & Carson
• “The Indeterministic Character of Evolutionary Theory”(1996)
• “drift clearly is a stochastic or probabilistic orindeterministic phenomenon” (324)
• “if one is a realist...then one should conclude that[evolutionary theory] is fundamentally indeterministic”(336)
Brandon & Carson
• “The Indeterministic Character of Evolutionary Theory”(1996)
• “drift clearly is a stochastic or probabilistic orindeterministic phenomenon” (324)
• “if one is a realist...then one should conclude that[evolutionary theory] is fundamentally indeterministic”(336)
But then...
• “the inferences we can make” about drift (322)
• what drift “can predict” or “cannot predict” (323)
• The “hidden variables” argument
• Response: Graves, Horan, & Rosenberg (1999)
But then...
• “the inferences we can make” about drift (322)
• what drift “can predict” or “cannot predict” (323)
• The “hidden variables” argument
• Response: Graves, Horan, & Rosenberg (1999)
But then...
• “the inferences we can make” about drift (322)
• what drift “can predict” or “cannot predict” (323)
• The “hidden variables” argument
• Response: Graves, Horan, & Rosenberg (1999)
A Reinterpretation
• What about probabilistic causation?
• Brandon’s causal reading of drift
• Back to hidden variables
A Reinterpretation
• What about probabilistic causation?
• Brandon’s causal reading of drift
• Back to hidden variables
A Reinterpretation
• What about probabilistic causation?
• Brandon’s causal reading of drift
• Back to hidden variables
Conclusions
• Conflations of “chance”:
• BC conflate at least three senses of “chance”
(unpredictability, causal indeterminism, probabilistic
causal processes)• Only on one of these does their argument go through• GHR conflate at least two senses of “chance”
(unpredictability, causal indeterminism)
• Arguments fail to engage
• But the distinctions are well-known!
Conclusions
• Conflations of “chance”:
• BC conflate at least three senses of “chance”
(unpredictability, causal indeterminism, probabilistic
causal processes)• Only on one of these does their argument go through• GHR conflate at least two senses of “chance”
(unpredictability, causal indeterminism)
• Arguments fail to engage
• But the distinctions are well-known!
Conclusions
• Conflations of “chance”:
• BC conflate at least three senses of “chance”
(unpredictability, causal indeterminism, probabilistic
causal processes)• Only on one of these does their argument go through• GHR conflate at least two senses of “chance”
(unpredictability, causal indeterminism)
• Arguments fail to engage
• But the distinctions are well-known!
