Concept
Counterfactual definiteness
Overview
Because of the importance of the observer effect and other factors, counterfactual definiteness (CFD) is an open question in quantum mechanics. Whether experts working in the field can speak "meaningfully" of the definiteness of the results of measurements that have not been performed is not known for certain. Theorists often assume definitely that various objects exist and that objects have certain properties, but under a counterfactual scenario (i.e., when no measurement is made), the scientific principles at work don't apply as cleanly, and such assumptions are not as solid as under rigorous experimental conditions. The term "counterfactual definiteness" is used in discussions of physics calculations, especially those related to the phenomenon called quantum entanglement and those related to the Bell inequalities. In such discussions "meaningfully" means the ability to treat these unmeasured results on an equal footing with measured results in statistical calculations. It is this (sometimes assumed but unstated) aspect of counterfactual definiteness that is of direct relevance to physics and mathematical models of physical systems and not philosophical concerns regarding the meaning of unmeasured results.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
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But occasionally, either the coherence or the verification fails. We then revise our conceptual scheme so as to preserve the general trust in the symbolic reference, while relegating definite details of that reference to the category of errors. Such errors are termed ‘delusive appearances.’ This error arises from the extreme vagueness of the spatial and temporal perspectives in the case of perception in the pure…
Alfred North Whitehead, Symbolism, its meaning and effect
States what Counterfactual definiteness is.
After how great a multiplication, then, of varied instances, all agreeing in no other antecedent except A, is the supposition of a plurality of causes sufficiently rebutted, and the conclusion that _a_ is connected with A divested of the characteristic imperfection, and reduced to a virtual certainty? This is a question which we can not be exempted from answering: but the consideration of it belongs to what is…
John Stuart Mill, A System of Logic, Ratiocinative and Inductive
States what Counterfactual definiteness is.
147.] (γ) When this externality (of actuality) is thus developed into a circle of the two categories of possibility and immediate actuality, showing the intermediation of the one by the other, it is what is called Real Possibility. Being such a circle, further, it is the totality, and thus the content, the actual fact or affair in its all-round definiteness.
Georg Wilhelm Friedrich Hegel, The Logic of Hegel
States what Counterfactual definiteness is.
Related ideas
- Classical physics
- Momentum
- Quantum mechanics
- Quantum entanglement
- Uncertainty principle
- Causality
- Counterfactual conditional
- Interpretations of quantum mechanics
- Copenhagen interpretation
- Existence
- Many-worlds interpretation
- Principle of locality
Place in the tradition
Part of Interpretations of quantum mechanics.
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