Anti-haecceitism, the identity of indiscernibles and physicalism

Alexander Roberts (2024) recently argues that, given some plausible auxiliary assumptions, anti-haecceitism, the thesis that necessarily every truth is necessitated by the qualitative truths, logically implies the identity of indiscernibles—the thesis that necessarily any qualitatively indiscernible individuals are the same. Roberts suggests that this observation might pose a challenge to anti-haecceitists who are convinced by Black’s (1952) famous example of a symmetric universe, which contains nothing but two duplicate iron spheres. In this paper, I argue that anti-haecceitists do have room to maneuver to get around of this problem. The proposed response will be based on an important distinction between two different interpretations of physicalism.