 This approach was considered for some time to be impossible as it seems to require first finding the general solution to Einstein's equations.However, with use of ideas involved in Dittrich's approximation scheme (built on ideas of Rovelli) a way to explicitly implement, at least in principle, a reduced phase space quantization was made viable.Avshalom Elitzur and Shahar Dolev argue that quantum mechanical experiments such as the Quantum Liar provide evidence of inconsistent histories, and that spacetime itself may therefore be subject to change affecting entire histories.