Abstract
The Hardy–Weinberg equilibrium has been argued by Sober, Stephens and others to represent the zero-force state for evolutionary biology understood as a theory of forces. I investigate what it means for a model to involve forces, developing an explicit account by defining what the zero-force state is in a general theoretical context. I use this account to show that Hardy–Weinberg equilibrium is not the zero-force state in biology even in the contexts in which it applies, and argue based on this that drift should not be understood as an evolutionary force.
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Notes
This simplifies Aristotelian physics. Actual Aristotelian mechanics doesn’t have a fully coherent treatment of rates of change. Our discussion of Aristotelian mechanics here will therefore be a somewhat idealized and anachronistic one, as suits our need to draw a particular conceptual contrast with Newtonian mechanics. The issue is that a fully coherent ‘Aristotelian’ view such as is presented here conflicts too obviously with empirical evidence. In particular, how velocity changes after a force is removed is a problem that historically meets various attempted solutions, which make the mechanics more empirically adequate but less conceptually pure; this account ignores these solutions. The difficulty can be understood as a tension between the idea that velocity must proportional to the force applied and should be zero in the absence of a force (which is key to our treatment of Aristotelianism), with the observation that a thrown object loses its velocity gradually, even though the force would appear to cease once the thrown object leaves the hand.
As well as the resistance to that force: in Aristotelian mechanics, the resistance of the medium is always factored into the velocity.
To be more precise, we might say that the magnitude of the force is the absolute value of the variable, since whether the variable is positive or negative just tells us the direction in which the force acts.
The difference is just that parameters aren’t subject to experimental manipulations—e.g. the gravitational constant.
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Acknowledgments
I would like to thank Denis Walsh, Samir Okasha, Jacob Stegenga, Philippe Huneman, Cory Lewis, Alex Djedovic, Fermin Fulda, Michael Cournoyea, Christopher Stephens and an anonymous reviewer for their helpful comments and encouragement.
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Earnshaw, E. Evolutionary forces and the Hardy–Weinberg equilibrium. Biol Philos 30, 423–437 (2015). https://doi.org/10.1007/s10539-014-9464-9
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DOI: https://doi.org/10.1007/s10539-014-9464-9