The narrator's state of mind vacillates wildly through the story, which is, of course, part of the design of his torturers. As the story opens, the narrator is in a semi-conscious state of mind. He begins by saying he is "sick unto death with that long agony," implying that he may have been physically tortured in some way. During the sentence, he begins to feel his senses leaving him. As he is carried down into the dungeon, he is unconscious, although he has glimmers of memory of being carried down.
As he regains consciousness, he begins to think clearly enough to want to determine his situation, so he begins to explore his prison. At one point he is so fatigued he falls asleep; when he wakes he resumes his exploration, but he is disoriented to the point he fails to realize he has gotten turned around. He trips, finding his face hanging into the pit. He becomes filled with terror and "agitated." He falls asleep, and wakens with great thirst. He drinks a drugged liquid and falls asleep again.
When he wakes up, he is strapped to a table with the pendulum far above him. He considers his situation, he prays, he struggles, he becomes "frantically mad," but finally a resignation takes over as he realizes he is going to die. As the pendulum gets closer and closer and he realizes the type of death he will die, he alternately laughs and howls, showing an unstable mental state. Only when the pendulum descends to about ten to twelve strokes away from him does he experience the "collected calmness of despair" that allows him to clearly devise an escape plan. While the rats are swarming over him, he experiences "disgust, for which the world has no name" but has the mental capacity to force himself to remain absolutely still.
When he escapes, he finds himself facing the eerie paintings of the demons and has a hard time persuading himself they are not real. As the wall close in, he has no time to think, and he screams in despair. As he is rescued by General Lasalle, he gives no insight into the state of his mind. However, one might assume that the traumas he endured would cause his moods and mental states to swing like a pendulum the rest of his life as he relives the horrors of his torture and the joy of his rescue.