Cristian Mariani

The Mass Density approach to GRW (GRWm for short) has been widely discussed in the quantum foundations literature. A crucial feature of GRWm is the introduction of a Criterion of Accessibility for mass, which allows to explain the determinacy of experimental outcomes thus also addressing the tails problem of GRW. However, the Criterion of Accessibility leaves the ontological meaning of the non-accessible portion of mass utterly unexplained. In this paper I discuss two viable approaches to non-accessible mass, which I call anti-realist and realist, and will defend the latter. First, I show that the anti-realist approach suffers from various objections. Second, I develop an account of non-accessible mass density states as objectively indeterminate states of affairs.

Barnes (2014) has argued in this journal for the following conditional: If there is any metaphysical indeterminacy, this must be at the most fundamental level of reality. To argue for this claim, Barnes relies on two principles that I shall call bivalent completeness and determinate link. According to the former, a complete description is a bivalent assignment of truth values to every sentence. The determinate link, instead, establishes that the determination relation between levels of reality preserves determinacy from one level to another. In response to Barnes’ conclusion, Eva (2018) has recently pointed out that bivalent completeness is question begging. In this paper, I will first show why Eva's line of reasoning can be resisted. My aim will then be to present a stronger case against Barnes’ argument by challenging the determinate link. In the presence of metaphysical indeterminacy, the link between fundamental and derivative facts might itself be the locus of indeterminacy. I will conclude by showing that Barnes and Eva make many unwarranted assumptions regarding both indeterminacy and fundamentality. The logical space around the connection between these two notions appears to be much wider than what they seem to be aware of, or so I will argue.

Many features of quantum mechanics (QM) suggest that, at the microscopic level, objects sometimes fail to determinately instantiate their properties. In recent years, many have argued that this phenomenon indicates the existence of an ontological kind of indeterminacy, often called metaphysical indeterminacy, which is supposed to affect the ontology of QM. As insisted by Glick ('Against Quantum Indeterminacy), however, once we look at the major realist approaches to QM we learn that the indeterminacy disappears from the description of the world at its most fundamental level. This absence might be taken as a good reason for adopting some form of eliminativism towards quantum mechanical indeterminacy. The aim of this paper is to distinguish three ways of defending eliminativism, and to argue that none of them eventually succeeds. The upshot is that QM does in fact suggest the existence of metaphysical indeterminacy, although only as an emergent phenomenon.

Explanations of the genuine openness of the future often appeal to objective indeterminacy. According to the received view, such indeterminacy is indeterminacy of certain future-tensed state of affairs that presently obtain. We shall call this view the weak indeterminate present, to distinguish it from the view we will defend in this paper, which we dub the strong indeterminate present. According to our view, unsettledness of the future is grounded on the present indeterminacy of some present-tensed state of affairs. In order for an indeterminate present-tensed state of affairs to explain the unsettledness of a future-tensed state of affairs, there has to be a connection between the two. We argue that this connection can only be provided if we look at the internal structure of the relevant state of affairs. Finally, we will suggest that the best background theory to explain the connection are the so-called spontaneous collapse models of quantum mechanics.