Believing something that is not based in reality is referred to as what?

The term that accurately describes the belief in something that is not based in reality is "delusion." Delusions are typically characterized as fixed false beliefs that are resistant to reason or confrontation with actual fact. This concept is often used in psychological contexts, referring to beliefs that an individual holds despite strong evidence to the contrary. For instance, someone may believe they have superhuman abilities or are being persecuted, even when this is clearly not the case.

In contrast, the other terms somewhat differ in meaning. An "illusion" often refers to a misinterpretation of a real external stimulus or event, whereas a "misconception" denotes a misunderstanding based on incorrect information or beliefs that may not be deeply ingrained or resistant to logic. "Fantasy" generally suggests imaginative or fanciful thoughts that are not necessarily meant to be taken as reality. While all four choices can involve elements of false belief or perception, "delusion" specifically captures the idea of an unwavering belief that contradicts reality.