“We can’t explain this result in terms of particles, but only in terms of ‘electron waves’. And whereas we might have been content enough to believe that electrons in a bright beam are wave-like and can be diffracted by the double slits, it is hard to understand how one-by-one passage of what seem to be particles (judging from the discrete bright spots that appear on the screen) can produce wave-like interference. We’re forced to conclude that ‘wave-like’ electrons can interfere with themselves.”