# SMuK 2021 – wissenschaftliches Programm

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# AGPhil: Arbeitsgruppe Philosophie der Physik

## AGPhil 3: Quantum Theory 2

### AGPhil 3.4: Vortrag

### Dienstag, 31. August 2021, 15:30–16:00, H5

**Derivative metaphysical indeterminacy and quantum physics** — •Alessandro Torza — Instituto de Investigaciones Filosóficas, UNAM

A growing literature regards quantum mechanics as a hotbed of metaphysical indeterminacy (MI), which is to say, indeterminacy with a nonrepresentational source. However, Glick (2017) has argued that quantum mechanics provides evidence of MI only if MI can be merely derivative (i.e., arising only at the nonfundamental level); and Barnes (2014) has argued that MI cannot be merely derivative. I will respond to both Glick and Barnes by providing two ways of understanding quantum mechanics as giving rise to merely derivative MI. My overarching argument is as follows:

1. MI is characterized relative to a logical space: MI arises in logical space L just in case there is a fact (state of affairs) in L which neither obtains nor fails to obtain.

2. A quantum system S defines both a classical logical space C_S (i.e., a logical space which is a model of classical logic) and a quantum logical space Q_S (i.e., a logical space which is a model of quantum logic). Crucially, MI arises in Q_S but not in C_S (Torza 2021).

3. Given a system S, there are two ways of understanding C_S as fundamental and Q_S as derivative: if a metaphysically privileged description of reality involves classical logic (Sider); and if reality is fundamentally isomorphic to a Hilbert space (Carroll & Singh ms).

4. Therefore, there are two ways of understanding quantum MI as arising derivatively (in Q_S) but not fundamentally (in C_S).