Quantum Theory and the Limits of Objectivity

TL;DR

This paper analyzes recent arguments questioning the objectivity of measurement outcomes in quantum theory, ultimately suggesting that even definite outcomes may not be fully objective.

Contribution

It clarifies and evaluates three recent arguments about the limits of objectivity in quantum measurement, emphasizing the significance of the third argument.

Findings

The first two arguments depend on assumptions about counterfactual outcomes.

The third argument successfully challenges the objectivity of measurement outcomes.

Even with definite outcomes, objectivity may be compromised.

Abstract

Three recent arguments seek to show that the universal applicability of unitary quantum theory is inconsistent with the assumption that a well-conducted measurement always has a definite physical outcome. In this paper I restate and analyze these arguments. The import of the first two is diminished by their dependence on assumptions about the outcomes of counterfactual measurements. But the third argument establishes its intended conclusion. Even if every well-conducted quantum measurement we ever make will have a definite physical outcome, this argument should make us reconsider the objectivity of that outcome.