yathoktam tasyaiva vyabhicārādau śabde 'pyavyabhicāriṇi / doṣavat sādhanaṃ jñeyaṃ vastuno vastusiddhitaḥ //
As has been stated: "Even when the verbal expression is free from deviation [from truth], the proof may be faulty in cases of deviation and the like, since a real thing can only be established by [another] real thing."