There are in fact at least five barbers, each of whom shaves himself if and only if he doesn't.

The most famous one, call him Bertrand, shaves all and only those who don't shave themselves.
Alfred, on the other hand, is shaved by all and only those who don't shave themselves.
Gottlob shaves all and only those who don't shave him.
Georg is shaved by all and only those whom he doesn't shave.
Augustus (my favourite) shaves all and only those whom he doesn't shave.

Chris G