▁but ▁is ▁determined ▁by ▁F res nel ' s ▁drag ging ▁coefficient , ▁by ▁c . ▁ ▁In ▁order ▁to ▁make ▁the ▁principle ▁of ▁relativ ity ▁as ▁required ▁by ▁Po inc ar é ▁an ▁exact ▁law ▁of ▁nature ▁in ▁the ▁imm obile ▁a ether ▁theory ▁of ▁Lor ent z , ▁the ▁introduction ▁of ▁a ▁variety ▁ad ▁h oc ▁hypoth eses ▁was ▁required , ▁such ▁as ▁the ▁contra ction ▁hypothesis , ▁local ▁time , ▁the ▁Po inc ar é ▁str esses , ▁etc .. ▁This ▁method ▁was ▁critic ized ▁by ▁many ▁sch ol ars , ▁since ▁the ▁assumption ▁of ▁a ▁consp i racy ▁of ▁effects ▁which ▁completely ▁prevent ▁the ▁discovery ▁of ▁the ▁a ether ▁dr ift ▁is ▁considered ▁to ▁be ▁very ▁impro b able , ▁and ▁it ▁would ▁viol ate ▁Occ am ' s ▁raz or ▁as ▁well . ▁Ein stein ▁is ▁considered ▁the ▁first ▁who ▁completely ▁disp ensed ▁with ▁such ▁auxili ary ▁hypoth eses ▁and ▁drew ▁the ▁direct ▁conclus ions ▁from ▁the ▁facts ▁stated ▁above : ▁that ▁the ▁relativ ity ▁principle ▁is ▁correct ▁and ▁the ▁directly ▁observed ▁speed ▁of ▁light ▁is ▁the ▁same ▁in ▁all ▁in ert ial ▁reference ▁frames . ▁Based ▁on ▁his ▁ax iom atic ▁approach , ▁Ein stein ▁was ▁able ▁to ▁derive ▁all ▁results ▁obtained ▁by ▁his ▁prede cess ors   – ▁and ▁in ▁addition ▁the ▁formulas ▁for ▁the ▁relativ istic ▁Do pp ler ▁effect ▁and ▁relativ istic ▁aber r ation   – ▁in ▁a ▁few ▁pages , ▁while ▁prior ▁to ▁ 1 9 0 5 ▁his ▁compet itors ▁had