*Watch Online/In person*:Psychosis is a mental state where people experience a 'different' world. If, as clinical psychiatry and neuroscience suggests, it is our 'default mental state' why isn't everyone psychotic? Psychosis does not arise de novo; external sensory input and cognition actively inhibit its expression. This lecture provides an understanding on how thin the boundary is between sanity and madness and what leads from one to the other; and to appreciate the frailty of rational thought