And Georg Strecker adds context: "The oldest undoubted instance is in Priscillian "Liber apologeticus" I.4 (CSEL 18.6). Priscillian was probably a Sabellianist or Modalist, whose principal interest would have in the closing statement about the heavenly witnesses ("and these three, the Father, the Word, the Holy Spirit, are one"). Here he found his theological opinions confirmed: that the three persons of the Trinity are only modes or manners of appearance of the one God. This observation caused some interpreters to suppose that Priscillian himself created the "Comma Johanneum". However, there are signs of the "Comma Johanneum", although no certain attestations, even before Priscillian...". In the early 1900s the Karl Künstle theory of Priscillian origination and interpolation was popular: "The verse is an interpolation, first quoted and perhaps introduced by Priscillian (a.d. 380) as a pious fraud to convince doubters of the doctrine of the Trinity."