The delusions definition states that when a person fixates upon a specific thought that is clearly false as being true, then they are in a state of delusion. The vast majority of delusions are found in patients with mental disorders or pathological conditions. The most frequent of these conditions are schizophrenia, paraphrenia, bipolar disorder, and psychotic depression. There are a number of common manifestations of this condition and certain terms have been coined to identify the various underlying conditions.

To be considered a real delusion, the problem must fit established delusions definition criteria. These were outlined by Karl Jaspers, a noted psychiatrist, in the year of 1917. His delusions definition is still used to this day by most specialists around the globe. In his definition, there are three specific criteria that must be met. The first is that the false beliefs are certain within the mind of the affected patient. The second condition is that the patient’s opinion of the matter cannot be changed when giving proof that the belief is untrue. The last condition is that the belief must be false or impossible in nature. These beliefs often are centered around a strange or bizarre subject matter. The one problem with this definition is that it works on the assumption that the beliefs of the majority of people are the correct beliefs while, in fact, there are many examples in history of situations where the majority of the people were clearly wrong.

Perhaps the most common of all modern day delusions are persecutory delusions. With this type, the patient feels that he or she is being unjustly persecuted. In some cases, the patient is able to identify the source, but for the vast majority, the persecutors are not readily apparent. This specific type of persecutory delusions frequently occur as part of overall schizophrenia delusions. The condition of schizophrenia is a mental disorder of which delusions are one of the main symptoms. Another example of schizophrenia delusions are patients that have delusions of grandeur. In these examples, the patient feels that they are a great person and somehow set apart from the rest of society. At the same time, the person will often feel that they are more powerful, frequently with supernatural abilities. The most common delusion of grandeur is when a patient believes that they are the reincarnation of Jesus Christ.

In modern times, some atheist writers have argued that there is one delusion that is more widespread than all others combined. This phenomenon is known as the god delusion. These writers, with Richard Dawkins being the most famous, state that a belief in god or another higher power is actually a delusion. By the clinical definition of the condition, this is technically a true statement. However, there is no way to provide proof for or against the existence of god. Therefore, the controversy has inspired lively debates and a number of books written about the subject. The application of delusions definition into the realm of religion has provided great insight into the psychology of humans.