Chapter 2 begins with classical medicine, exploring the sources of so-called Hippocratic medicine, nosological and clinical, as well as other lesser-known authors from the fourth century BCE such as Diocles and Praxagoras. The limited material preserved on our topic from Hellenistic medicine (Herophilus and Erasistratus) is also surveyed. The richest information is preserved by the writings of the Hippocratic Corpus, where phrenitis first appears, and where it is richly described, both in nosological profiles and with reference to specific patients. Its core traits are by this point established: fever, localization in the chest , and an association with winter also showed by the co-morbidity with, and analogy to, pleuritis and pneumonia. Interestingly, the phren/phrenes are seldom mentioned in discussions of phrenitis, and when they are, not in their traditional, ‘Homeric’ psychological function, or directly as locus affectus, thus signalling a desire to distance the pathological narrative from traditional poetic models.

Self-reported wellbeing is correlated with activity in a number of brain areas. The sensation of pain is most clearly experienced in the anterior cingulate cortex which registers both physical pain and social pain.

The mind affects the body and vice versa. Wellbeing predicts mortality as well as smoking does. Prolonged psychological stress leads to excessive production of adrenaline/epinephrine and cortisol, over-activity of the immune system and to excessive inflammation in the body. Equally, the body affects the mind. This is obvious in the effects of drugs, recreational and psychiatric.

Our genes have important effects on our wellbeing. We know this in two ways. Identical twins (who have identical genes) are much more similar to each other in their wellbeing than are non-identical twins. Adopted children are more similar in mental health to their biological parents than to the parents who raised them. It is however not possible to neatly separate the effects of the genes and the environment for two reasons: (1) Genes and environment often interact in their effects on wellbeing. (2) Genes and the environment are correlated.