“BS!”, like “bull!”, “crap!”, “humbug!”, “buncome!” and similar expressions, can seriously damn a rival’s claim or their personal authority. It can also serve as a jest or dismissive riposte. In any case, the nature of BS is notoriously difficult to pin-point. Several philosophers–who have been accused of spreading more than their share of it–have theorized accounts of BS. The most famous account comes from Harry Frankfurt, whose small book On Bullshit. was a literary sensation almost 20 years ago. Peter Ludlow takes Frantfurt to task.