For the first time ever I encountered the dark night of the soul. I experienced depression caused by cognitive dissonance at the deepest level. Cognitive dissonance is the result of two contradicting beliefs, usually one is an established belief, and considered to be truth, and the second is discovered, thereby challenging the first. Most of the time our brains simply dismiss the second discovery as not being possible because of it's contradiction with the established truth. However, if the new discover is compelling enough then our mind must struggle to determine which is true. It is this struggle, the dissonance of competing truths, that can make us feel sick. There are many examples of mental dissonance, some are small and hardly noticeable, others rock our boat. The most potent example I can think of is when a friend is accused of murder, our first response is denial, and then we feel it in our guts.
Our minds have a process for collecting, comparing, and verifying information. Everyday, and thanks to technology more than ever before, our minds are bombarded with information. We can't give conscious consideration to everything that our senses experience. Most of the sorting happens at a subconscious level, many times a second our brains collect, compare, verify, over and over and over. In that shuffle if something comes up as new idea, then our mind searches for supporting evidence. If something comes up as being in conflict with an existing verified truth, then the mind denies and dismisses the conflicting information labelling it FALSE. When our minds are young and flexible these moments are no big deal. However by our middle or late middle years, we are so heavily invested in our truths that these moments of conflict are like a fire alarm.
The real problem happens when we discover recurring evidence against a foundational truth. The question then becomes, what if my foundational truth isn't actually true? Well, the truth is that many things we hold as true, are only true, as Forrest Gump would say, "Cuz that's what my Mama told me." We can't dismiss the significance of the trusted figure bias.
This explains how pathological liars function, they simply install their own lie in the truth slot. Then they go on to establish new evidence based on the lie and so on and so on. It also explains how we put up with slavery, and racism, and sexism, and, and, and. Furthermore, it certainly helps us understand why there are so many religions. We believe and then declare the truth.
Thankfully there is another brain function which provides balance, unfortunately it has been shunned for a long long time. The function I'm referring to is discernment. It's a kind of the double check mechanism, but it only operates on the conscious side of the mind. We have to exercise it. So while our subconscious is happily stamping true on thousands of pieces of throughput, we have to be consciously running quality control. We have to constantly be critiquing our own database.
My point here is that when we hit a bump on the road of life, and the doubt light goes on, it's not a bad thing.