2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91379Experimental evidence, the heuristics of indistinguishability, and its logical inconsistency with quantum formalism all argue against the existence of a quantum mixture uncorrelated with the exterior, that is, argue for the postulate "The state of a system uncorrelated with its exterior is pure." This is shown to be equivalent with "The state of a system describable in terms of indistinguishable pure states is pure," and with "The state of the universe is pure"; further, it yields a quantitative expression of the traditional relation of welcher Weg information to partial coherence. It is concluded that all mixtures are "improper," the trace-reduction of a composite system's pure state.13pp. Replaces quant-ph/0110052 v2: Numerous small edits. Thm 6 proof improved. Main reason for post: My working e-mail address, <kirkpatrick@nmhu.edu> (address on abstract page may be broken)Quantum Physicstext