  This correlational property is also ‘responsible’ for the action at a distance that the orthodox theory seems to postulate between the distant wings in the EPR/B experiment. Recall (section 1) that Einstein, Podolsky and Rosen thought that this curious action at a distance reflects the incompleteness of this theory rather than a state of nature. The EPR argument for the incompleteness of the orthodox theory is controversial. But the orthodox theory seems to be incomplete for a different reason. This theory postulates that in non-measurement interactions, the evolution of states obeys a linear and unitary equation of motion, the so-called Schrödinger equation (see the entry on quantum mechanics), according to which the particle pair in the EPR/B experiment remains in an entangled state. This equation of motion also dictates that in a spin measurement, the pointers of the measurement apparatuses get entangled with the particle pair in a non-separable state in which (according to the theory's property assignment, see below) the indefiniteness of particles’ spins is ‘transmitted’ to the pointer's position: In this entangled state of the particle pair and the pointer, the pointer lacks any definite position, in contradiction to our experience of perceiving it pointing to either ‘up’ or ‘down.’