The idea that the dynamical properties of quantum systems are invariably relative to other systems has recently regained currency. Using Relational Quantum Mechanics (RQM) for a case study, this paper calls attention to a question that has been underappreciated in the debate about quantum relativism: the question of whether relativity iterates. Are there absolute facts about the properties one system possesses relative to a specified reference, or is this again a relative matter, and so on? It is argued that RQM (...) (in its best-known form) is committed to what I call the Unrestricted Iteration Principle (UIP), and thus to an infinite regress of relativisations. This principle plays a crucial role in ensuring the communicability and coherence of interaction outcomes across observers. It is, however, shown to be incompatible with the widespread, conservative reading of RQM in terms of relations, instead necessitating the adoption of the more unorthodox notion of perspectival facts. I conclude with some reflections on the current state of play in perspectivist versions of RQM and quantum relativism more generally, underscoring both the need for further conceptual development and the importance of the iteration principle for an accurate cost-benefit analysis of such interpretations. (shrink)

Quantum mechanics is one of the most successful theories of physics. But the creators of quantum mechanics had to reject realism in order to describe some paradoxical quantum phenomena. Einstein considered the rejection of realism unacceptable, since according to his understanding, realism is the presupposition of every kind of physical thinking. The dispute about the permissibility of rejecting realism has largely determined the modern understanding of quantum theory and even led to the emergence new quantum information technologies. Many modern authors (...) are sure that realism can be refute experimentally. Some authors are sure even that real technologies can be created on the basis of this refutation. The well-known GHZ theorem is considered critically in this work the authors of which are sure that realism can be refute experimentally. (shrink)

According to High-Dimensional Wavefunction Fundamentalism (HDWF) the wavefunction field evolving in configuration space is all that exists fundamentally. The main argument in favor of HDWF is an argument from separability and locality: separability is a desirable feature of a fundamental metaphysics and HDWF is indeed such a separable metaphysics. Separability in turn is desirable because it is simple and intuitive. Tim Maudlin has recently argued that intuitiveness and simplicity cannot motivate separability. In particular, our intuitions stem from our interactions with (...) the three-dimensional world which is non-separable. Therefore, he concludes, there is _nothing else_ HDWF theorists can appeal to motivate separability. I call this Maudlin’s challenge. The present paper addresses Maudlin’s challenge by showing how the facts that some plurality of entities are separable entail that its constituents are fundamental, for well-motivated notions of fundamentality. (shrink)