Final answer:
Hippocrates classified mental disorders into three categories: mania, melancholia, and phrenitis, focusing on natural rather than supernatural causes.
Step-by-step explanation:
The three categories that Hippocrates classified mental disorders into were mania, melancholia, and phrenitis. Hippocrates, often referred to as the "father of Western medicine," proposed that mental illnesses had natural causes. For instance, he attributed mania and melancholia to imbalances in the body's four humors, while phrenitis was believed to be an inflammation of the brain. This classification by Hippocrates was revolutionary for its time, shifting perspectives from supernatural explanations to naturalistic and biological causes for mental disorders.