Maren Bräutigam
University of Cologne
There are largely three views on whether Leibniz’s Principle of the Identity of Indiscernibles (PII) is violated by similar particles. According to the earliest view, PII is always violated (call this the no discernibility view). According to the more recent weak discernibility view, PII is valid in a weak sense. No and weak discernibility have been referred to as orthodoxy. Steven French has argued that although PII is violated, similar particles can still be regarded as individuals. However, as it is equally possible to argue that similar particles are non-individuals, French famously concluded that metaphysics is underdetermined by physics. Call this thesis orthodox underdetermination. Most recently, some authors have turned against orthodoxy by arguing that PII is valid in more than a weak sense – call this the new discernibility view, also referred to as heterodoxy. Since heterodoxy is backed up by physical considerations, metaphysics now seems to be determined by physics: physics indicates that PII is valid. In this paper, I raise the question whether heterodoxy – despite appearances – is just as underdetermined as orthodoxy; in other words, I examine the possibility of heterodox underdetermination. This question is motivated as follows: according to Tomasz Bigaj, the worst problem for heterodoxy is what he calls the ambiguity of individuation. This problem arises (partly) due to the flexibility of the mathematical formalism (think of, e.g., basis transformations) and makes it hard to pin down an unambiguous ontological interpretation of a given state. As I will argue, the specific ambiguity problem which arises with respect to entangled states might be solved by going holist, i.e., by advocating that entangled states do not contain two numerically distinct particles, but one holist entity instead. However, the particularist, who wishes to maintain the picture with two numerically distinct particles, also has options to react to the ambiguity problem. Therefore, a sort of underdetermination arises: with respect to entangled states, both particularism and holism seem to be viable options. The crucial follow-up question is whether these two ontological interpretations of entangled states allow for different explanations of the most peculiar feature of entanglement, i.e., the violation of Bell inequalities.
Chair: Cristina Somcutean
Time: September 6th, 17:30-18:00
Location: SR 1.007
SOPhiA 2026 