No physicist has ever "seen" an electron, yet, all physicists believe in existence of electrons . An intelligent but superstitious man advances this analog to argure that 'ghosts' exist even though no one has "seen" one . How will you refute his argument ?

Explanation

Many phenomena which depend upon the existence of electrons have been predicted and actually observed in everyday life. There is no phenomenon which can be explained on the basis that ghosts exist though they are not seen. So, obviously, the comparison between two situations does not make any sense.