What is doubt? To paraphrase American legal jargon is there both reasonable doubt and unreasonable doubt and so we need delve into the question of unreasonable doubt in the sense as constituting a rather common psychological affliction indeed.
Unreasonable doubt is a form of cognitive dissonance which if persistent typically causes significant pain. As other types of cognitive dissonance does unreasonable doubt emerge from conflict between the two brains. How does this occur and appear? The agency of the subconscious protects the agency of the conscious by means of warning the conscious of actual, potential or imaginary danger.
Although originally almost identical do the two brains of the human cranium with time develop into becoming increasingly distinctive from one another in having individual trajectories of development in ageing. There can however with time also develop increasing harmony in cooperation, collaboration and division of powers between the two brains.
When the subconscious of one of the two brains warns of a danger that the conscious is still unaware of may this cause a conflict with the subconscious of the other brain which may disagree about the risk/threat assessment or simply have different priorities in terms of acceptance of risk exposure.
Of course, an assessment or calculus of the subconscious of one of the two brains is not necessarily rational, reasonable and/or well-founded since a subconscious must have imperfections just as as has the conscious.
The question thus arises as to the nature of communication between the respective subconsciouses of the two brains in the human cranium? Subconscious communication is communication between subconsciouses of brains of two or more persons (i.e. neurological contact) and so there is no reason to believe that the two subconsciouses of the two parallel human brains cannot communicate with each other as well.
The problem however relates to the equal nature of the two brains. Most human beings are either right-handed or left-handed, yet there is not necessarily any such order of priority between the two brains of the human cranium. The absence of a clear chain of command or division of powers between the two brains is hence often the origin of psychological doubt which may cause severe emotional suffering indeed and significantly affect/impair the functioning of an individual human person.
One reason this has proven difficult to manage is that the mechanisms behind it have remained unknown. The combination of the subconscious providing clues (including inducing protective fear) and conflicts of priority and assessment between the two brains means that this may become quite confusing in conscious experience.
The relative difficulty in treating psychological afflictions is largely due to almost complete lack of understanding of how the four sentient agencies of cognition interact with each other, both within a brain and between the two brains in the human cranium.
Human beings generally thus need to individually learn and discover how to create a harmonious, customised relationship, indeed partnership between the two brains and so constructively resolve conflicts between them; including if helpful devising a functional division of authority and powers. We also need learn how the subconscious communicates with the conscious by means of the subconscious providing clues, warnings, hopes and pieces of information that serve to quite effectively guide (alternatively misguide) the conscious.
We need thus all learn rational brain management; meaning how we can become more emotionally rational in developing constructive relationships between the four non-singular sentient agencies of cognition within the human cranium.