ABSTRACT
Thus far, in all cases where we have encountered electric currents, our analyses did not depend on, nor differentiate between, the possible signs of the charge borne by the carriers. In other words, a given phenomenological [macroscopic] current could be achieved [microscopically] by either positive charge carriers drifting in the forward direction, or negative charge carriers drifting in the reverse direction. Nothing that has been considered until now allows one to distinguish between the two possible microscopic scenarios.
