Explanation and the quantum state

This paper argues that there are good reasons to adopt a non‐reductive account of states when it comes to quantum mechanics. That is to say, it is argued that there are advantages to thinking about states as sui generis, as reducible to classes of values of quantities, when it comes to the quantum domain. One reason for holding this view is that it seems to improve the prospects for explanation. In more detail, it is argued that there is an “explanatory shortfall” in the quantum domain owing to the failure of value definiteness. To remedy this situation, two proposals are put forward about the nature of the quantum state: Proposal A, that the quantum state is the only first‐order property of quantum systems, Proposal B, that the quantum state is one first‐order property among many. These proposals seem equally good.