live ) ▁+ ▁m ▁( E ither ) ▁and ▁the ▁“ D ead ” ▁pla us ibility ▁is ▁m ( D ead ) ▁+ ▁m ( E ither ). ▁Finally , ▁the ▁“ E ither ” ▁pla us ibility ▁sums ▁m ( A live )   +   m ( D ead )   +   m ( E ither ). ▁The ▁universal ▁hypothesis ▁( “ E ither ” ) ▁will ▁always ▁have ▁ 1 0 0 % ▁belief ▁and ▁pla us ibility — it ▁acts ▁as ▁a ▁check sum ▁of ▁sorts . ▁ ▁Here ▁is ▁a ▁somewhat ▁more ▁elaborate ▁example ▁where ▁the ▁behavior ▁of ▁belief ▁and ▁pla us ibility ▁begins ▁to ▁emer ge . ▁We ' re ▁looking ▁through ▁a ▁variety ▁of ▁det ector ▁systems ▁at ▁a ▁single ▁far away ▁signal ▁light , ▁which ▁can ▁only ▁be ▁col oured ▁in ▁one ▁of ▁three ▁colours ▁( red , ▁yellow , ▁or ▁green ): ▁ ▁Events ▁of ▁this ▁kind ▁would ▁not ▁be ▁mode led ▁as ▁dis joint ▁sets ▁in ▁probability ▁space ▁as ▁they ▁are ▁here ▁in ▁mass ▁assignment ▁space . ▁R ather ▁the ▁event ▁" Red ▁or ▁Y ellow " ▁would ▁be ▁considered ▁as ▁the ▁union ▁of ▁the ▁events ▁" Red " ▁and ▁" Y ellow ", ▁and ▁( see ▁probability ▁ax i oms ) ▁P ( Red ▁or ▁Y ellow ) ▁ ≥ ▁P ( Y ellow ), ▁and ▁P ( Any )   =   1 , ▁where ▁Any ▁refers ▁to ▁Red ▁or ▁Y ellow ▁or ▁Green . ▁In ▁D ST ▁the