Speakable and Unspeakable in the Tunneling Time Problem

A simple solution is given to the tunneling time problem from the viewpoint of interfering alternatives. Using Gell-Mann and Hartle's decoherence functional for real time Feynman histories, it is shown that (i) the probability distribution of tunneling times cannot be defined for “resident time” type but (ii) the range of values of the time is definable. The range turns out to be so broad for opaque barriers that a unique tunneling time cannot be considered even in a loose sense.