US-P18.158ab ।US-P18.158cd ॥
In plain words
The thought "I am the witness" is something the intellect settles on; it is not the witness's own thought. The witness carries no mark that would set it apart — because there is no other there to set it apart from.
Close to the Sanskrit
The knowledge 'I am the witness' is a determination of the intellect alone, not of the witness — because of its having no distinguishing feature, since for it there exists no other.