The only way charge can be detected is via its field. Gauss's Law gives
the details, and "displacement" "current" is a natural development from
Gauss's Law. The only thing wrong with it is the name, which is related
to the fluid-field analogies which also brought us permittivity, and which
guided Faraday and others in their investigations. Do your students have
the intuition, or the spirited willingness to guess, that characterized
those investigators?