In the Feynman's discussion of double slit experiment,
even when the intensity of the source is so low that
there is a single electron between the source and the
screen, the interference patterns are different for the
cases of 1) single slit open and 2) both the slits open.
This means that both the slits influence the course that
the electron will take and we can say without beating around
the bush that a single electron goes through both the slits!!!