 Definitions of delusions are based on the behavior we exhibit when experiencing a delusion rather than on the underlying mechanisms responsible for our behavior. The behavior associated with having delusions is often described in epistemic terms, using concepts such as belief, truth, rationality, evidence, and justification. For instance, delusions may be defined as beliefs held with conviction in spite of having little empirical support (where the epistemic concepts are in italics). According to the Glossary in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV 2000, p. 765 and DSM-5 2013, p. 819), delusions are false beliefs based on incorrect inference about external reality that persist despite evidence to the contrary: