To all these heretics is added one Tatian, a brother-heretic. This man was Justin Martyr’s disciple. After Justin’s death he began to cherish different opinions from his. For he wholly savours of Valentinus; adding this, that Adam cannot even attain salvation: as if, when the branches become salvable, the root were not!
Appendix: Against All Heresies
Trans. by Rev. S. Thelwall
Note: This quote is a good warning for us. It doesn’t matter who your teacher is, you can still fall from faith and become a heretic or unbeliever.