 A straightforward but naive interpretation of this equation according to which the probability reflects ignorance concerning the path taken does not work because the right hand side of Eq. (\ref{eq:feynman}) is not a sum of positive numbers (interpretable as probabilities of trajectories) but rather a positive number obtained by taking the modulus squared of a sum of complex numbers. Wharton explores the prospects for giving an ignorance interpretation of the path integral along less straightforward lines, noting that Eq. (\ref{eq:feynman}) can be brought into the form 