In quantum mechanics, the consistent histories or simply "consistent quantum theory" interpretation generalizes the complementarity aspect of the conventional Copenhagen interpretation. The approach is sometimes called decoherent histories and in other work decoherent histories are more specialized.

There are two problems with the Copenhagen interpretation: it requires observers to collapse wavefunctions, without defining observers - which are impossible to define. it provides no model of reality, merely gives an ambiguous recipe for results of experiments.

Einstein saw Quantum Theory as a means to describe Nature on an atomic level, but he doubted that it upheld "a useful basis for the whole of physics." He thought that describing reality required firm predictions followed by direct observations.

They just want the equations to produce reliable results when they plug in numbers. The Copenhagen interpretation remains a fulcrum around which much of quantum mechanics turns, yet it's not universally endorsed within the scientific community.