"Beyond belief" is an idiomatic expression that is sometimes employed to convey the sense that a certain type of information or event is difficult to accept in light of traditional thoughts and understandings. A number of different situations may trigger a sense of being beyond belief, including actions taken by another person. The general idea behind this English saying is that something does not fit easily into what is known and accepted and is thus in some manner extraordinary. The nature of that extraordinary idea or event may be either a positive or a negative.
In terms of behavior, being beyond belief involves engaging in actions that are outside the scope of what is normally expected. For example, the idea that someone who appears to be happily married and devoted to a spouse would one day leave home and hearth to run off to a desert island with a new love interest is so far out of character that people would have a hard time believing that the devoted spouse was capable of such actions. In like manner, the idea that a businessperson with a reputation for honesty and integrity who chooses to engage in some type of activity that is underhanded and possibly illegal may be considered beyond belief by many people.
New theories of theology or science may also be greeted by skeptics as being beyond belief. Over time, those theories may eventually gain some ground in certain quarters and seem somewhat less disconnected from what is commonly accepted in those respective spheres. In the interim, the theory remains beyond belief, and outside the scope of what is considered acceptable and common in general.
It is very important to understand that "beyond belief" may be used in a positive or a negative connotation. When negative, the usage normally implies that something is unacceptable and should be avoided at all costs, else the normal balance will be thrown off and chaos will result. At the same time, something may be beyond belief and inspire wonderful visions for something better than what is known in the here and now. The latter application has often applied when humankind has envisioned technological advances that only a few years before were not even considered, much less investigated. With this in mind, being beyond belief may cause some upset to the status quo, but may also ultimately lead to advancements in just about any aspect of humanity that is to the benefit of all concerned.