Philosophical and scientific investigations into the nature of belief and knowledge are ancient, extending back to the beginnings of rational thought. It is not until the last few decades that we have been able to peer into and examine the organ of belief, the brain. Neuroanatomical perspectives have begun to address the long-standing questions of epistemology by identifying specific neural regions that are critical for the storage and evaluations of beliefs. Here, a novel neuroanatomical model of belief and doubt is presented, where post-rolandic association cortices are critical for the storage of beliefs and the prefrontal cortex is necessary for the doubt and evaluation process. It is proposed that the singular function of the prefrontal cortex is "false tagging" (the neuroanatomical essence of doubt) to mental representations in post-rolandic cortices. Individuals that have dysfunction to the prefrontal cortex, such as patients with explicit damage to the prefrontal cortex, from tumor resections or cerebral vascular events, should show a "doubt deficit", accompanied by a general increased belief to information. Evidence is presented indicating that deficiencies in the "false tagging" function may explain a wide assortment of abnormalities in neurological and psychiatric patients. Several experiments in various populations (neurological, developmental, and psychiatric) were conducted to examine the role of specific brain regions in the believing and doubting process. First, two studies gave participants explicitly-labeled false beliefs and measured the ability of the participants to falsify these beliefs. It was predicted that participants with dysfunction to the prefrontal cortex would be poor at falsifying novel beliefs. Results confirmed the predictions. Second, participants were given pairs of statements that represented opposite opinions on some issue and responded by agreeing or disagreeing with each statement. Participants with dysfunction to the prefrontal cortex, who, theoretically, have a "doubt deficit," should show compartmentalized minds, where cognitions are easily believed but rarely doubted against other extant mental information. Results suggested that participants with prefrontal cortex dysfunction were more likely to agree to opposing statements. Third, individuals with dysfunction to the prefrontal cortex should lack a dissonant state that can change attitudes, when two cognitions are in conflict. Using a free-choice paradigm, it was found that participants with prefrontal dysfunction showed either extreme attitude change after choice or no attitude change after choice, which is consistent with a "no dissonance" state. Finally, individuals with compartmentalized minds tend evince an authoritarian personality. A psychometric scale and a behavioral measure of authoritarianism were examined in the participants. Results indicated that participants with prefrontal cortex dysfunction showed increased authoritarianism on the psychometric scale, but decreased authoritarian behavior, reflecting a dissociation between knowledge and behavior. In conclusion, the results support the theoretical assertions that the prefrontal cortex is critical for "false tagging" or doubting cognitive representations. Data from neurological, developmental, and psychiatric populations are broadly consistent with the theory and offer strong external validity.