While allusions to psychoses in the West date back to ancient Greek medicine and literature, the modern concept of schizophrenia is generally attributed to the German psychiatrist Emil Kraepelin (b. 1856–d. 1926). His description of schizophrenia as a syndrome composed of a diverse collection of seemingly unrelated symptoms that tended to co-occur across patients forms the basis for our modern diagnosis. According to the Diagnostic and Statistical Manual of the American Psychiatric Association (DSM-IV-TR), the diagnosis of schizophrenia requires two or more of the following manifestations of psychosis: delusions; hallucinations; disorganized speech; disorganized or catatonic behavior; or negative symptoms, such as lacking normal emotional responses to events, lacking normal levels of motivation, or a reduced flow of speech.