Not only is the imagined scene in a suspension of time, but it is told from the third person limited point of view that assists with a "suspension of disbelief" on the part of the reader.  This point of view was begun three paragraphs prior to the beginning of Section II, so Bierce has surreptitiously already caught the reader into believing what follows.  Added to this, the metaphoric parallels of reality and Farquhar's imaginings run throughout the narrative making its verisimilitude only ambiguous.  For instance, Farquhar

had power only to feel...He was conscious of motion.  Encompassed in a luminous cloud, of which he was now merely the fiery heart, without material substance, he swung through unthinkable arcs of oscillation, like a vast pendulum.  [He is really swinging from the hangman's rope.]

The tremendous and lengthy detail joined by emotional diction sweeps the reader into the current of Farquhar's imagination; that is, until the jolting shift of point of view in the last paragraph, which reports the reality.