As H. H. Holmes planned to use the atmosphere of the World’s Columbian Exposition to his advantage, he focused on achieving his ends to the exclusion of all other purposes. In doing so, he exhibited obsessive behavior, sometimes called monomania. In addition, because he showed a total disregard for the norms of society that would typically restrain someone from such behavior, he is considered to have been a psychopath.

While Holmes on some level enjoyed inflicting harm and pain on his victims and even fatal injuries, Larson admits that his exact motives remain unclear. Larson quotes Holmes as saying that he was helpless to resist being a murderer, blaming the devil for his behavior. Yet Holmes was methodical and careful in carrying out his plans, including the hotel’s construction, so he was clearly aware that his actions needed to be disguised or hidden.

While Holmes stood to profit by many of his actions, there were numerous other ways he could have earned the desired income. Sadism was perhaps the primary motivator, in that he derived satisfaction from fulfilling his desire for the victims to feel pain. He often took deliberate actions and addition time to inflict the pain of torture rather than to show mercy.