Abstract In this paper, I challenge the distinction between “epistemic” and “ontic” states propounded by Harrigan and Spekkens (Found Phys 40:125–157, 2010) by pointing out that because knowledge is factive, any state that represents someone’s knowledge about a physical system thereby also represents something about the physical system itself, so there is no such thing as “mere knowledge”. This criticism leads to the reformulation of the main question of the debate: instead of asking whether a given state is ontic or epistemic, we should instead ask whether a given change of a state is ontic or epistemic. In particular, in the context of quantum mechanics, one can ask whether the collapse of the quantum state could be understood as an epistemically successful change of the observer’s beliefs about the complete state of the system that is not associated with any change in the physical reality. I argue that the answer to this question should be in the negative because it is possible that, in a series of measurements, the collapse rule tells us to update a certain state to a different one and then back to the same state; if both of these updates are merely changes of our beliefs, then they could not both be epistemically successful.Abstract In this paper, I challenge the distinction between “epistemic” and “ontic” states propounded by Harrigan and Spekkens (Found Phys 40:125–157, 2010) by pointing out that because knowledge is factive, any state that represents someone’s knowledge about a physical system thereby also represents something about the physical system itself, so there is no such thing as “mere knowledge”. This criticism leads to the reformulation of the main question of the debate: instead of asking whether a given state is ontic or epistemic, we should instead ask whether a given change of a state is ontic or epistemic. In particular, in the context of quantum mechanics, one can ask whether the collapse of the quantum state could be understood as an epistemically successful change of the observer’s beliefs about the complete state of the system that is not associated with any change in the physical reality. I argue that the answer to this question should be in the negative because it is possible that, in a series of measurements, the collapse rule tells us to update a certain state to a different one and then back to the same state; if both of these updates are merely changes of our beliefs, then they could not both be epistemically successful.

Foundations of PhysicsDec 30, 20224 citations

Determinism Is Ontic, Determinability is Epistemic

Harald Atmanspacher A

Philosophical discourse traditionally distinguishes between ontology and epistemology and generally enforces this distinction by keeping the two subject areas separated. However, the relationship between the two areas is of central importance to physics and philosophy of physics. For instance, many measurement-related problems force us to consider both our knowledge of the states and observables of a system (epistemic perspective) and its states and observables independent of such knowledge (ontic perspective). This applies to quantum systems in particular. This contribution presents an example showing the importance of distinguishing between ontic and epistemic levels of description even for classical systems. Corresponding conceptions of ontic and epistemic states and their evolution are introduced and discussed with respect to aspects of stability and information flow. These aspects show why the ontic/epistemic distinction is particularly important for systems exhibiting deterministic chaos. Moreover, this distinction provides some understanding of the relationships between determinism, causation, predictability, randomness, and stochasticity.Philosophical discourse traditionally distinguishes between ontology and epistemology and generally enforces this distinction by keeping the two subject areas separated. However, the relationship between the two areas is of central importance to physics and philosophy of physics. For instance, many measurement-related problems force us to consider both our knowledge of the states and observables of a system (epistemic perspective) and its states and observables independent of such knowledge (ontic perspective). This applies to quantum systems in particular. This contribution presents an example showing the importance of distinguishing between ontic and epistemic levels of description even for classical systems. Corresponding conceptions of ontic and epistemic states and their evolution are introduced and discussed with respect to aspects of stability and information flow. These aspects show why the ontic/epistemic distinction is particularly important for systems exhibiting deterministic chaos. Moreover, this distinction provides some understanding of the relationships between determinism, causation, predictability, randomness, and stochasticity.

May 1, 200127 citations

How to spell out the epistemic conception of quantum states

Simon Friederich

Studies in History and Philosophy of Science Part B Studies in History and Philosophy of Modern PhysicsJun 30, 201113 citations

An Epistemic model of Quantum State with Ontic Probability Amplitude

Arun Kumar Pati, Partha Ghose, A. K. Rajagopal

We first prove that ontological models of the quantum state which are capable of reproducing the Born probability rule and fall in the class of $ψ$ -epistemic models are inconsistent with the Sch{ö}dinger time evolution. We then model the ontic state space as a complex projective Hilbert space that embeds the projective Hilbert space of quantum mechanics and define a minimalist epistemic state as an average over a set of "hidden states" in the larger space. We show that such a model incorporates probability amplitudes and admits an epistemic interpretation of quantum states. Finally, we prove a second theorem to show that such a model is compatible with locality but ontic models are not.We first prove that ontological models of the quantum state which are capable of reproducing the Born probability rule and fall in the class of $ψ$-epistemic models are inconsistent with the Sch{ö}dinger time evolution. We then model the ontic state space as a complex projective Hilbert space that embeds the projective Hilbert space of quantum mechanics and define a minimalist epistemic state as an average over a set of "hidden states" in the larger space. We show that such a model incorporates probability amplitudes and admits an epistemic interpretation of quantum states. Finally, we prove a second theorem to show that such a model is compatible with locality but ontic models are not.

arXiv:1401.4104Jan 16, 20140 citations

The nature of a quantum state

James G. Gilson

Acta physica HungaricaDec 1, 19863 citations

We first prove that ontological models of the quantum state which are capable of reproducing the Born probability rule and fall in the class of

ψ

-epistemic models are inconsistent with the Sch{ö}dinger time evolution. We then model the ontic state space as a complex projective Hilbert space that embeds the projective Hilbert space of quantum mechanics and define a minimalist epistemic state as an average over a set of "hidden states" in the larger space. We show that such a model incorporates probability amplitudes and admits an epistemic interpretation of quantum states. Finally, we prove a second theorem to show that such a model is compatible with locality but ontic models are not.