  There is an extensive philosophical literature on the interrelated issues of
identity, individuality, and distinguishability in quantum systems. A key
consideration is whether quantum systems are subject to a strong form of
individuality termed "haecceity" (from the Latin for "this-ness"). I argue that
the traditional, strong form of haecceity does not apply at the quantum level,
but that in order to properly account for the need for symmetrization in
quantum systems, a weaker kind of haecceity must be involved, which I call
"quantum haecceity." In the process, I also question some generally accepted
tenets of the current debate, such as the idea that symmetrization of states
for identical quanta must be postulated and reflects permutation invariance.
Instead, I note that a perturbative Hamiltonian is required for exchange
effects, which suggests that the need for symmetrization arises from specific
physical conditions.
