Hippocrates tends towards body and nature-based explanations for all illnesses, including mental ones. He believes the Four Humours are responsible for personality characteristics. For instance, a blood imbalance is seen as the cause of aggressiveness in self-centered people. Hippocrates and his contemporaries also recognize diseases like depression and anxiety and believe there might be a physical explanation for dreams.

Hippocrates believes the body consists of four Humours. To stay healthy, these Humours – blood, phlegm, yellow bile, and black bile – must remain in balance.

Hippocrates dismisses the idea that magic, spirits, or the gods can cause or cure disease.. Like many Greeks, he believes everything is comprised of the four physical elements-air, water, fire, and earth. Therefore, he thinks physical things like human action and the four seasons are responsible for disease and healing. When one or more of the Humours is unstable, treatments are prescribed to restore balance. Common therapies include laxatives, purging, and bleeding. Most treatments also involve rest, fresh air, good food, and water. In addition, herbal remedies are used to treat pain while a disease runs its natural course.