INDISCERNIBILITY > Origins Like uncertainty and complementary, indiscernibility is a feature that must be added to physical descriptions if certain pictures imported from classical physics are to work in the explanation of quantum phenomena. Thus, for example the strong requirement of individuality involved in the classical concept of particle must be relaxed in order to account for the fact that, in quantum mechanics, indistinguishable paths do not contribute individually to the predictions, but rather interfere.

Quantum field theory, which is the relativistic generalization of quantum mechanics, does not contain any direct reference to labeled particles. However, the phenomena it deals with can be partially understood in terms of interacting particles. An example is provided by the high energy processes that are interpreted as the creation and annihilation of elementary particles.

Under some assumptions, the quantum mechanical treatment of identical particles can be derived from quantum field theory, which also provides an explanation for the connection between spin and statistics (in particle language, this is the fact that particles with integer spin are bosons whereas particles with half-integer spin are fermions). As we show in the section on Pauli's exclusion principle, the statistical behavior of ensembles of identical particles is determined by the symmetry properties imposed upon their global quantum state by the indiscernibility principle.