6: 2 to screw in the bulb and 4 to testify that it was lit from the moment they began screwing.
or
Five. One to screw it in and four to tell him how bitchin' he looked doing it.
or
Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or
None. Agnostics question whether electricity really exists.
or
In their Sleevies!
or