Humean Supervenience, Composition as Identity and Quantum Wholes

In this paper, we focus on two related reductive theses in metaphysics—<i>Humean Supervenience</i> and <i>Composition as Identity</i>—and on their status in light of the indications coming from science, in particular quantum mechanics. While defenders of these reductive theses (at least those who do not simply deny the metaphysical import of empirical data and their proposed interpretation) claim that they can be updated so as to resist the quantum evidence, we provide arguments against this contention. We claim that physics gives us reason for thinking that both <i>Humean Supervenience</i> and <i>Composition as Identity</i> are at least contingently false, as the very process of composition determines, at least in some cases, the nature of composed systems. The argument has essentially to do with the fact that denying the reductive theses in question allows one to provide better explanations for the quantum evidence.