▁a ▁compat ibil ist ▁and ▁she ▁has ▁just ▁sat ▁down ▁on ▁the ▁so fa , ▁then ▁she ▁is ▁committed ▁to ▁the ▁claim ▁that ▁she ▁could ▁have ▁remained ▁standing , ▁if ▁she ▁had ▁so ▁desired . ▁But ▁it ▁follows ▁from ▁the ▁consequence ▁argument ▁that , ▁if ▁Jane ▁had ▁remained ▁standing , ▁she ▁would ▁have ▁either ▁generated ▁a ▁contradiction , ▁viol ated ▁the ▁laws ▁of ▁nature ▁or ▁changed ▁the ▁past . ▁Hence , ▁compat ibil ists ▁are ▁committed ▁to ▁the ▁existence ▁of ▁" in cred ible ▁ab ilities ", ▁according ▁to ▁G inet ▁and ▁van ▁In wagen . ▁One ▁response ▁to ▁this ▁argument ▁is ▁that ▁it ▁equ iv oc ates ▁on ▁the ▁not ions ▁of ▁ab ilities ▁and ▁necess ities , ▁or ▁that ▁the ▁free ▁will ▁ev oked ▁to ▁make ▁any ▁given ▁choice ▁is ▁really ▁an ▁ill usion ▁and ▁the ▁choice ▁had ▁been ▁made ▁all ▁along , ▁ob liv ious ▁to ▁its ▁" dec ider ". ▁David ▁Lewis ▁suggests ▁that ▁compat ibil ists ▁are ▁only ▁committed ▁to ▁the ▁ability ▁to ▁do ▁something ▁otherwise ▁if ▁different ▁circumstances ▁had ▁actually ▁obtained ▁in ▁the ▁past . ▁ ▁Using ▁T , ▁F ▁for ▁" true " ▁and ▁" false " ▁and ▁? ▁for ▁und ec ided , ▁there ▁are ▁exactly ▁nine ▁positions ▁regarding ▁determin ism / free ▁will ▁that ▁consist ▁of ▁any ▁two ▁of ▁these ▁three ▁possibilities : ▁ ▁In compat ibil ism ▁may ▁occup y ▁any ▁of ▁the ▁nine ▁positions ▁except ▁( 5 ), ▁( 8 ) ▁or ▁( 3 ), ▁which ▁last ▁corresponds ▁to ▁soft ▁determin ism