Individuality, quasi-sets and the double-slit experiment

Quasi-set theory Q allows us to cope with certain collections of objects where the usual notion of identity is not applicable, in the sense that x=x is not a formula, if x is an arbitrary term. Q was partially motivated by the problem of non-individuality in quantum mechanics. In this paper, I discuss the range of explanatory power of Q for quantum phenomena which demand some notion of indistinguishability among quantum objects. My main focus is on the double-slit experiment, a major physical phenomenon which was never modeled from a quasi-set-theoretic point of view. The double-slit experiment strongly motivates the concept of degrees of indistinguishability within a field-theoretic approach, and that notion is simply missing in Q. Nevertheless, other physical situations may eventually demand a revision on quasi-set theory axioms, if someone intends to use it in the quantum realm for the purpose of a clear discussion about non-individuality. I use this opportunity to suggest another way to cope with identity in quantum theories.