Patrick Hayden
Stanford University

Project Title

Agency, Simulation, and Counterfactual Computation

Project Summary

There is an inherent tension between our agency—our ability to freely choose our actions—and the apparent predictability of the physical world. How is it possible to reconcile the freedom to choose implicit in most people’s definition of ‘agency’ with what the laws of physics tell us, which is that given perfect knowledge of the past what we will choose is perfectly predictable? In this project, we will explore the consequences for this question that arise from the fact that the physical world is fundamentally quantum. Some have said that quantum mechanics destroys predictability and rescues agency. We will argue the opposite. We will argue that quantum mechanics in an important sense makes the behavior of agents more rather than less predictable. This is because the existence of quantum mechanics allows us to use the technique of `quantum counterfactual computation’ to predict the choices of supposedly free agents. We will show how this impacts various thought experiments about free will, and explore the implications for our understanding of agency in the physical world.



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