«إِلَّا أَنْ يُوَثِّقَهُ غَيْرُ مَنْ يَنْفَرِدُ عَنْهُ عَلَى الْأَصَحِّ»
According to the preferred view, an endorsement by someone other than the narrator’s sole reporting pupil may remove the deficiency.
This qualification shows that having only one known pupil does not create permanent ignorance. Independent attestation by a qualified critic acquainted with the person can supply the missing critical knowledge.
An endorsement must still be evaluated responsibly: the endorser’s competence, basis of acquaintance, and contrary evidence matter. This is a qualified critical rule, not a license to treat any unexplained use of “thiqah” as conclusive.