 If instead we assume that quantum mechanics is itself applicable to the description of measurements, then the question becomes one of how one should model a measurement within quantum theory, specifically as some appropriate interaction between a ‘system’ and an ‘apparatus’, and of whether by so doing one can derive from the unitary evolution for the total system of system and apparatus the three phenomenological aspects of quantum measurements: that measurements have results, that these results obtain with some characteristic probabilities, and that depending on the result of a measurement the state of the system is generally transformed in a characteristic way (for this subdivision of the problem, see Maudlin 1995). This derivation, however, appears to be impossible.