 Another point in favour of the new theory is that it handles cases of ‘trumping’ preemption, first described by Jonathan Schaffer (2000a). Lewis gives an example involving a major and a sergeant who are shouting orders at the soldiers. The major and sergeant simultaneously shout ‘Advance!’; the soldiers hear them both and advance. Since the soldiers obey the superior officer, they advance because the major orders them to, not because the sergeant does. So the major’s command preempts or trumps the sergeant’s. Other theories have difficulty with trumping cases, including – or so Lewis believes – his own attempt to solve the late preemption problem by appealing to quasi-dependence (2000, 184-5). The trumping case is one in which the causal chain leading from the sergeant’s shout to the soldiers’ advancing runs to completion – or at least, Lewis thinks, it is epistemically possible that it does – just as the chain leading from the major’s shouting does. So it is an intrinsic duplicate of the comparison case where the sergeant shouts but the major doesn’t; hence the soldiers’ advancing quasi-depends on the sergeant’s shout, which is the wrong result. Lewis’s argues that his new theory handles trumping cases with ease. Altering the major’s command while holding fixed the sergeant’s, the soldier’s response would be correspondingly altered. In contrast, altering the sergeant’s command, while holding fixed the major’s, would make no difference at all.