 Delusions used to be divided into functional and organic. Now the distinction is regarded by most obsolete, at least in its original characterization. A delusion was called ‘organic’ if it was the result of brain damage (usually due to injuries affecting the right cerebral hemisphere). A delusion was called ‘functional’ if it had no known organic cause and was explained primarily via psychodynamic or motivational factors. It has become more and more obvious with the development of neuropsychiatry that the two categories overlap. Today, the received view is that there is a biological basis for all types of delusions, but that in some cases it has not been identified with precision yet. Some studies have reported very little difference between the phenomenology and symptomatology of delusions that were once divided into organic and functional (Johnstone et al. 1988).