. ▁In ▁ 1 8 3 8 , ▁the ▁religious ▁phil os opher ▁Christian ▁Hermann ▁We isse ▁developed ▁a ▁theory ▁about ▁this . ▁He ▁post ulated ▁a ▁hypoth et ical ▁collection ▁of ▁Jesus ' ▁say ings ▁from ▁an ▁additional ▁source ▁called ▁Q , ▁taken ▁from ▁Qu elle , ▁which ▁is ▁German ▁for ▁" source ". ▁If ▁this ▁document ▁existed , ▁it ▁has ▁now ▁been ▁lost , ▁but ▁some ▁of ▁its ▁material ▁can ▁be ▁dedu ced ▁indirect ly . ▁Compar ing ▁what ▁is ▁common ▁to ▁Matthew ▁and ▁Luke , ▁yet ▁absent ▁in ▁Mark , ▁the ▁critical ▁scholar ▁Heinrich ▁Julius ▁Hol tz mann ▁demonstrated ▁( in ▁ 1 8 6 3 ) ▁the ▁probable ▁existence ▁of ▁Q ▁well ▁enough ▁for ▁it ▁to ▁be ▁accepted ▁as ▁a ▁likely ▁second ▁source , ▁along ▁with ▁Mark , ▁for ▁Matthew ▁and ▁Luke . ▁ ▁This ▁allowed ▁the ▁two - source ▁hypothesis ▁to ▁emer ge ▁as ▁the ▁best ▁supported ▁of ▁the ▁various ▁syn opt ic ▁solutions . ▁There ▁is ▁also ▁material ▁unique ▁to ▁each ▁g ospel . ▁This ▁indicates ▁additional ▁separate ▁sources ▁for ▁Matthew ▁and ▁for ▁Luke . ▁Bib lic al ▁scholar ▁B . ▁H . ▁Stre eter ▁used ▁this ▁insight ▁to ▁ref ine ▁and ▁expand ▁the ▁two - source ▁theory ▁into ▁a ▁four - source ▁theory ▁in ▁ 1 9 2 5 . ▁ ▁While ▁most ▁sch ol ars ▁agree ▁that ▁the ▁two - source ▁theory ▁offers ▁the ▁best ▁explanation ▁for ▁the ▁Syn opt ic ▁problem , ▁it ▁has ▁not ▁gone ▁without ▁dispute . ▁The ▁Syn opt ic ▁Sem