 However, can we now draw the conclusion that the momentum is only imprecisely defined? Certainly not. Before the position measurement, its value was \(p_{i}\), after the measurement it is \(p_{f}\). One might, perhaps, claim that the value at the very instant of the position measurement is not yet defined, but we could simply settle this by a convention, e.g., we might assign the mean value \((p_{i} + p_{f})/2\) to the momentum at this instant. But then, the momentum is precisely determined at all instants, and Heisenberg’s formulation of the uncertainty principle no longer follows. The above attempt of completing Heisenberg’s argument thus overshoots its mark.