Second, the positive and negative energy that Wolf talks about are all virtual in the context of Feynman diagrams. For example, the photon exchanged between two electrons is virtual. Virtual photons are merely mathematical entities whose pictorial representations are found to be convenient in theoretical calculations. Virtual particles and processes could have observable effects only if they interact with an external field. And this observable effect is not seeing particles and antiparticles or positive and negative energies, but a small perturbation in an existing physical quantity. One such effect, called Lamb shift, resulting from vacuum polarization and its interaction with the Coulomb force between the electron and proton of a hydrogen atom, is measured as a very small contribution to the energy levels of the hydrogen atom.
All the theoretical discussion in the quotation above is only a distraction for the insertion of the last six words. We could replace the words “spirit” and “soul” with any other pair of words, and nobody can tell us that our choice is less appropriate than “spirit” and “soul,” because, ultimately, they are all “suggestions.”